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HE 1.1.14 1 Leading nucleon and the proton-nucleus inelasticity | We present in this paper a calculation of the average proton-nucleus inelasticity. Using an Iterative Leading Particle Model and the Glauber model, we relate the leading particle distribution in nucleon-nucleus interactions with the respective one in nucleon- proton collisions. To describe the leading particle distribution in nucleon-proton collisions, we use the Regge Mueller formalism. ::: Contribution to 26th ICRC - Salt Lake City, Utah. August, 1999. ::: HE 1.1.14 | We study the effects of gluon radiation on top production and decay processes at an $e^+e^-$ collider.The matrix elements are computed without any approximations, using spinor techniques. We use a Monte Carlo event generator which takes into account the infrared singularity due to soft gluons and differences in kinematics associated with radiation in the production versus decay process. The calculation is illustrated for several strategies of top mass reconstruction. | eng_Latn | 26,900 |
Hysteresis and unusual magnetic properties in the singular Heusler alloy Ni45Co5Mn40Sn10 | An attractive strategy for the discovery of new materials is to combine a big first order phase transformation and interesting electromagnetic properties. 1 The change in lattice parameters at transformation, together with the lattice-parameter-sensitivity of electromagnetic properties, suggests the two phases can have diverse properties. While such phase transformations are sometimes not reversible, there is increasing evidence that certain conditions for low hysteresis 1–4 promote cyclic reversibility. The alloy | The neutrinoproduction of $\phi$ and $D^+_s$ mesons is studied, using the data obtained with the SKAT bubble chamber at the Serpukhov accelerator. It is found that the $\phi$ production occurs predominantly in the forward hemisphere of the hadronic c.m.s. (at $x_F > 0$, $x_F$ being the Feynman variable), with the mean yield strongly exceeding the expected yield of directly produced $\phi$ mesons and varying from $ 0) > = (0.92\pm0.34) \cdot 10^{-2}$ at $W > $ 2 GeV up to $(1.23\pm0.53) \cdot 10^{-2}$ at $W >$ 2.6 GeV and $(1.44\pm0.69) \cdot 10^{-2}$ at $W >$ 2.9 GeV, $W$ being the invariant mass of the hadronic system. The yield of leading $D^+_s$ mesons carrying more than $z = 0.85$ of the current $c$- quark energy is estimated: at $W > 2.9$ GeV, $ 0.85) > = (6.64\pm1.91) \cdot 10^{-2}$. It is shown, that the shape of the $\phi$ meson differential spectrum on $x_F$ is reproduced by that expected from the $D^+_s \to \phi X$ decays which, however, can account for only the half of the measured $\phi$ yield. | eng_Latn | 26,901 |
Radial Partition Enzyme Immunoassay | Radial Partition Immunoassay permits highly sensitive measurements of both low and high molecular weight ligands. The entire immunoassay is conducted on a small section of filter paper and assays can be done in less than 10 minutes. A variety of labels can be used with the technology including enzymes, fluorophores, chromophores or radioisotopes. We have achieved a high degree of sensitivity using enzyme labels and fluorescent readout of enzyme activity. The general principles of the radial partition enzyme immunoassay system are illustrated in Fig. 1. | Abstract A very promising spin physics programme will be soon on the way at the BNL Relativistic Heavy Ion Collider (RHIC). By studying the spin asymmetries for various processes (single photon, single jet and W ± production), we will compare the different predictions obtained using some sets of polarized parton distributions, available in the recent literature. We will put some emphasise on the analysis of the anticipated errors, given the event rates expected from this high luminosity new machine and the current acceptance for the detector systems at RHIC. | deu_Latn | 26,902 |
Analytic Structure of the Quark Propagator in a Model with an infrared vanishing Gluon Propagator | The Dyson-Schwinger equation for the quark self-energy is solved in the rainbow approximation using an infrared (IR) vanishing gluon propagator that introduces an IR mass scale {ital b}. There exists a {ital b}-dependent critical coupling indicating the spontaneous breakdown of chiral symmetry. If one chooses realistic QCD coupling constants the strength and the scale of spontaneous chiral symmetry breaking decouple from the IR scale for small {ital b} while for large {ital b} no dynamical chiral symmetry breaking occurs. At timelike momenta the quark propagator possesses a pole, at least for a large range of the parameter {ital b}. Therefore, it is suggestive that quarks are not confined in this model for all values of {ital b}. Furthermore, we argue that the quark propagator is analytic within the whole complex momentum plane except on the timelike axis. Hence the naive Wick rotation is allowed. {copyright} {ital 1995 The American Physical Society.} | Preparation of 1, 1-difluorobenzocyclopropene (4) and of its 2, 5- and 3, 4-dideuterio derivatives 4a and 4b is reported. Upon ionization in cold fluorosulfonic acid, 4 affords 1-fluorobenzocyclopropenium ion (6). 1H- and 13C-NMR. spectra of 4 and 6 are assigned on the basis of the data for the specifically deuteriumlabelled compounds 4a and 6a. Hydrolysis of 6a leads to 2, 5-dideuteriobenzoic acid (7a). | eng_Latn | 26,903 |
Internal shock model for the radio emission of Microquasars | The superluminal radio components observed in microquasars are usuallyinterpreted as individual ejection events. We discuss some of theshortcomings of this model and propose the internal shock model inquasi-continuous relativistic jets as an alternative. This model canresolve the problems with the single ejection model and is inagreement with radio observations. We outline some further testablemodel predictions some of which are already confirmed by observations. | The dependence of the differential cross section ${\mathrm{d}\sigma}/{\mathrm{d}p_{\perp}}$ of inclusive heavy quark production in pp and $\bar{\mathrm{p}}$p collisions on the renormalization and factorization scales is investigated. The implications of our results for experiments at TEVATRON and LHC are discussed. In particular, it is shown that the NLO QCD predictions for $\bar{t}t$ production at the LHC based on the Principle of Minimal Sensitivity are by 30-50% higher than the standard ones. | eng_Latn | 26,904 |
New textures for the lepton mass matrices | Abstract We study predictive textures for the lepton mass matrices in which the charged-lepton mass matrix has either four or five zero matrix elements while the neutrino Majorana mass matrix has, respectively, either four or three zero matrix elements. We find that all the viable textures of these two kinds share many predictions: the neutrino mass spectrum is inverted, the sum of the light-neutrino masses is close to 0.1 eV, the Dirac phase δ in the lepton mixing matrix is close to either 0 or π , and the mass term responsible for neutrinoless double-beta decay lies in between 12 and 22 meV. | The latest results from ATLAS and CMS on single top quark production and rare production channels of top quarks at the LHC are presented. | eng_Latn | 26,905 |
NASA probe spurs fresh view of Mercury's interior | A sulphur-rich shell could encase tiny planet's massive core. | The last few years, 2013-2016, the high energy neutrino events in ICECUBE and the last rich UHECR maps by AUGER and TA were hopefully opening a new High Energy astronomy age. Unfortunately the foreseen correlation between neutrino with best gamma X sources has not (yet) been found. The most celebrated GRB gamma sources do not correlate to any neutrino events. The expected Local Group anisotropy in UHECR within the nuleon GZK cut off, has just fade away. UHECR events from Virgo are almost absent. Above two hundred TeV energy tau neutrino might shine by double bang in detectable way in ICECUBE. Within a dozen of events no tau neutrino arised (yet) in ICECUBE. Finally GRBs Fireball models calling since decades for HE neutrinos correlated imprint at TeVs energy are not (yet) found. So many absences are making a huge question mark: is there a new reading key? | eng_Latn | 26,906 |
Method for managing the operation of a source of electrical energy storage, including a supercapacitor | The source of electrical energy storage is able to deliver in a short time a large electric power to an electrical load to enable a functional unit provided that a predetermined control is applied to this unit fonctionnelle.Selon the invention, the method comprises, before enabling said functional unit, to determine the temperature and, if said temperature is below a predetermined temperature, performing at least once the steps of connecting (D) said electric load said source of electrical energy storage without applying said predetermined command, and then reload (R) said source of storage, said electrical load is then reconnected and said control applied to said functional unit to operate (DEM). | We compute the O(alpha_t alpha_s) two-loop corrections to the neutral Higgs boson masses in the Minimal Supersymmetric extension of the Standard Model. An appropriate use of the effective potential allows us to obtain simple analytical formulae, valid for arbitrary values of mA and of the mass parameters in the stop sector. We elucidate some subtleties of the effective potential calculation, and find full agreement with the numerical output of the existing diagrammatic calculation. We discuss in detail the limit of heavy gluino. | eng_Latn | 26,907 |
RELATIVISTIC DIRECT INTERACTION BETWEEN NUCLEONS DERIVED FROM CLASSICAL FIELD THEORY | In order to achieve a realistic description of nuclear matter properties, the nonlinear interactions between nucleons can be introduced into the quantum model on the basis of nonlinear coupling constants solutions to the classical equations for meson fields. In this connection, the quantization of the classical theory is firstly considered in the case of linear solutions. The obtained model is applied to reproduce the "liquid–gas" phase transition in nuclear matter. | In this article we are discussing the nature and mechanism of the huge ::: amount of heat generation in Megawatts Energy Catalyzers (E-cat) of Andrea ::: Rossi that are able to change the energetics of our civilization in general. ::: These processes are new effects of Unitary Quantum Theory and do not relate to ::: either chemical or nuclear reactions or phase transfer. | yue_Hant | 26,908 |
Influence of Ingesting a Flavonoid-Rich Supplement on the Metabolome and Concentration of Urine Phenolics in Overweight/Obese Women | This study evaluated the effect of ingesting a flavonoid-rich supplement (329 mg/d) on total urine phenolics and shifts in plasma metabolites in overweight/obese female adults using untargeted metabolomics procedures. Participants (N = 103, 18–65 y, BMI ≥ 25 kg/m2) were randomized to flavonoid (F) or placebo (P) groups for 12 weeks with blood and 24 h urine samples collected prestudy and after 4 and 12 weeks in a parallel design. Supplements were prepared as chewable tablets and included vitamin C, wild bilberry fruit extract, green tea leaf extract, quercetin, caffeine, and omega 3 fatty acids. At 4 weeks, urine total phenolics increased 24% in F versus P with similar changes at 12 weeks (interaction effect, P = 0.041). Groups did not differ in markers of inflammation (IL-6, MCP-1, CRP) or oxidative stress (oxLDL, FRAP). Metabolomics data indicated shifts in 63 biochemicals in F versus P with 70% from the lipid and xenobiotics superpathways. The largest fold changes in F were measured for three gut-deriv... | We discuss flavor violation in large N Composite Higgs models. We focus on scenarios in which the masses of the standard model fermions are controlled by hierarchical mixing parameters, as in models of Partial Compositeness. We argue that a separation of scales between flavor and Higgs dynamics can be employed to parametrically suppress dipole and penguin operators, and thus effectively remove the experimental constraints arising from the lepton sector and the neutron EDM. The dominant source of flavor violation beyond the standard model is therefore controlled by 4-fermion operators, whose Wilson coefficients can be made compatible with data provided the Higgs dynamics approaches a"walking"regime in the IR. Models consistent with all flavor and electroweak data can be obtained with a new physics scale within the reach of the LHC. Explicit scenarios may be realized in a 5D framework, the new key ingredient being the introduction of flavor branes where the wave functions of the bulk fermions end. | eng_Latn | 26,909 |
Hadronic production of the doubly charmed baryon via the proton-nucleus and the nucleus-nucleus collisions at the RHIC and LHC | We present a detailed discussion on the doubly charmed baryon $\Xi_{cc}$ production at the RHIC and LHC via the proton-nucleus ($p$-N) and nucleus-nucleus (N-N) collision modes. The extrinsic charm mechanism via the subprocesses $g+c\to (cc)[n]+\bar{c}$ and $c+c\to (cc)[n]+g$ together with the gluon-gluon fusion mechanism via the subprocess $g+g\to(cc)[n]+\bar{c}+\bar{c}$ have been taken into consideration, where the intermediate diquark is in $[n]=[^1S_0]_{\bf 6}$-state or $[^3S_1]_{\bar{\bf 3}}$-state, respectively. Total and differential cross sections have been discussed under various collision energies. To compare with the $\Xi_{cc}$ production via proton-proton collision mode at the LHC, we observe that sizable $\Xi_{cc}$ events can also be generated via $p$-N and N-N collision modes at the RHIC and LHC. For examples, about $8.1\times10^7$ and $6.7\times10^7$ $\Xi_{cc}$ events can be accumulated in $p$-Pb and Pb-Pb collision modes at the LHC within one operation year. | During the course of an investigation into domestic radon levels in Northamptonshire, two hourly sampling real-time radon detectors were operated simultaneously in separate locations 2.25 km apart in Northampton, in the English East Midlands, for a 25-week period. This period of operation encompassed the period in September 2002 during which the Dudley earthquake (magnitude - 5.0) and smaller aftershocks occurred in the English West Midlands, UK. We report herein our observations regarding the occurrence of simultaneous short-period radon anomalies and their timing in relation to the Dudley, and other, earthquakes which occurred during the monitoring period. Analysis of the radon time-series reveals a short period when the two time-series displayed simultaneous in-phase short-term (6-9 h) radon anomalies prior to the main Dudley earthquake. Subsequent investigation revealed that a similar period occurred prior to another smaller but recorded earthquake in the English Channel. | eng_Latn | 26,910 |
Trapped ion emulation of electric dipole moment of neutral relativistic particles | The electric dipole moments of various neutral elementary particles, such as neutron, neutrinos, certain hypothetical dark matter particles and others, are predicted to exist by the standard model of high energy physics and various extensions of it. However, the predicted values are beyond the present experimental capabilities. We propose to simulate and emulate the electric dipole moment of neutral relativistic particles and the ensuing effects in the presence of electrostatic field by emulation of an extended Dirac equation in ion traps. | Abstract We present a convenient analytical parametrization, in both configuration and momentum spaces, of the deuteron wave-function calculated with the Paris potential. | eng_Latn | 26,911 |
Studies of ribosomal proteins of yeast species and their hybrids gel electrophoresis and immunochemical cross-reactions | The cytoplasmic ribosomal proteins (r-proteins) of seventeen yeast species of the genera Saccharomyces and Kluyveromyces were analyzed by one-dimensional gradient polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate. The electrophoretic patterns of cytoplasmic r-proteins from different species display extensive differences in both the 40S and the 60S subunit. Relatedness of species suggested by r-protein patterns correlates well with that based on DNA/DNA homology (Bicknell and Douglas 1970). Immunochemical cross-reactions and antibiotic susceptibility tests were also used to compare different species. Analyses of r-proteins from two different interspecific hybrids showed that their ribosomes were hybrid, containing r-proteins from both parents. These findings are discussed in relation to the evolution of yeast species and the regulation of expression of r-proteins in eucaryotes. | A good deal is known by now on the so-called jellium model of the homogeneous electron liquid. However, much of the quantitative progress at experimentally realizable densities has come from quantal computer simulation. Therefore, we here consider a homogeneous Fermion liquid with ‘artificial’ repulsive interaction λ/(rij )2 between Fermions i and j at separation rij . We discuss first of all the way the static structure function S(q), essentially the Fourier transform of the pair correlation function, is changed because of non-zero λ from the ‘Fermi hole’ form due entirely to Pauli principle effects between parallel spin Fermions. Unlike jellium with e 2/rij repulsive interactions, S(q) is proportional to q at long wavelengths, whereas the plasmon in jellium annulls the q term and S(q) is quadratic in q as q tends to zero. However for λ/(rij )2 interactions, the coefficient of q appearing in the Fermi hole structure factor, is renormalized by particle repulsions. Then some discussion is given of Fermion ... | eng_Latn | 26,912 |
Potential for increasing protein production by legume inoculation | The world food problem has been discussed in terms of food production for a rapidly expanding population, a large portion of which is already undernourished. | Recent results from CERN experiment NA36 are discussed and compared with models. These results refer to reactions of sulfur and protons of momentum 200 GeV/c per nucleon on a lead target. The [Lambda] spectrum for the sulfur beam was found to peak at mid-rapidity rather than target rapidity as observed in the proton induced reactions. This result indicates different reaction mechanisms are active. We discuss in some detail the analysis methods used. The data are consistent with the assumption of a fireball of high strangeness content being created at mid-rapidity in S [plus] Pb reactions. | eng_Latn | 26,913 |
Aggregation and fast diffusion of dye molecules on air–glycerol interface observed by confocal fluorescence microscopy | Abstract Diffusion processes of Rhodamine 6G (Rh6G) dye molecules dissolved in a small hemisphere drop of glycerol on a cover glass were investigated by using a confocal fluorescence microscope equipped with an objective lens with a high numerical aperture (NA = 1.35). Photon burst signals from Rh6G molecules in the bulk glycerol and on the air–glycerol interface of the hemisphere drop were separately detected at a single molecule level. The analysis of the photon burst signals by a correlation function method reveals that a sizable portion of the Rh6G molecules in the drop are aggregated on the air–glycerol interface and diffuse two-dimensionally on it, while the rest diffuse molecularly in the bulk. The aggregates are found to have a diffusion constant 15 times as large as that of the Rh6G molecule in the bulk glycerol, although the aggregates have a hydrodynamical radius much larger than that of a Rh6G molecule. | Abstract Recently we proposed the hypercubic smearing (HYP) that improves the flavor symmetry of staggered fermions by an order of magnitude with only minimal distortions at small distances. We describe a new algorithm to simulate dynamical HYP fermions based on the standard pure gauge overrelaxation and heatbath updates. The algorithm has been used to simulate four and two flavors of staggered fermions. Unlike standard dynamical simulation techniques, this algorithm does not loose efficiency at small quark masses. | eng_Latn | 26,914 |
Surface hydrogenation of silicon nanocrystallites during pulsed laser ablation of silicon target in hydrogen background gas | The surface hydrogenated silicon nanocrystallites can be prepared by pulsed laser ablation of a silicon target in hydrogen background gas. Formation processes of the surface Si–H bonds were found by correlation between the surface structure of the deposited nanocrystal film and the time- and space-resolved spectra of plume emission during the deposition. A precursor of the hydrogenation is SiH species created in blast-wave stage by collision between ejected Si species and background hydrogen gas. Results of plume diagnostics indicate that the spatial or temporal separation between Si and SiH species is not an origin of the formation of the surface hydrogenated Si nanocrystallite. It is concluded that the correlation between the thermal stability of the Si–H bond and the temperature variation of the formed nanoparticle during the deposition is important for the formation of the chemical bonding on the surface. | Abstract Recently we proposed the hypercubic smearing (HYP) that improves the flavor symmetry of staggered fermions by an order of magnitude with only minimal distortions at small distances. We describe a new algorithm to simulate dynamical HYP fermions based on the standard pure gauge overrelaxation and heatbath updates. The algorithm has been used to simulate four and two flavors of staggered fermions. Unlike standard dynamical simulation techniques, this algorithm does not loose efficiency at small quark masses. | eng_Latn | 26,915 |
The High Density Effects in Heavy Quark Production at pA Colliders | In this paper we investigate the role of the high density effects in the heavy quark production cross section in $pA$ processes at RHIC and LHC. We use, as initial condition, a gluon distribution consistent with fixed target nuclear data and the Glauber-Mueller approach to describe the high density effects. We show that this process can be used as a probe of the presence of the high density effects. Moreover, we include these effects in the calculation of the heavy quark production in $AA$ collisions, verifying that they cannot be disregarded both in the estimates of quarkonium suppression and in the initial conditions of the quark-gluon plasma. | Abstract Exotic pentaquark baryon with strangeness +1, Θ+, is studied in the QCD sum rule approach. We derive sum rules for the positive and negative parity baryon states with J= 1 2 and I=0. It is found that the standard values of the QCD condensates predict a negative parity Θ+ of mass ≃1.5 GeV, while no positive parity state is found. We stress the roles of chiral-odd condensates in determining the parity and mass of Θ+. | eng_Latn | 26,916 |
Kinematical Constraints on QCD Factorization in the Drell-Yan Process | We study factorization schemes for parton shower models in hadron-hadron collisions. As an example, we calculate lepton pair production mediated by a virtual photon in quark--anti-quark annihilation, and we compare factorized cross sections obtained in the conventional $\bar{\rm MS}$ scheme with those obtained in a factorization scheme in which a kinematical constraint due to parton radiation is taken into account. We discuss some properties of factorized cross sections. | This paper discusses the dynamical properties of p-spin models with Kac interactions. For large but finite interaction range R one finds two different well separated time scales for relaxation. A first short time scale, roughly independent of R, on which the system remains confined to limited regions of the configuration space and an R dependent long time scale on which the system is able to escape from the confining regions. I will argue that the R independent time scales can be described through dynamical mean field theory, while non-perturbative new techniques have to be used to deal with the R dependent scales. | eng_Latn | 26,917 |
Modeling of a Lagrangian Flamelet with Radiation Interaction | Abstract The burning history of a spherical diffusion flame element (Lagrangian flamelet) is modeled under three distinctive burning conditions: a quasi-steady burning process, a quasi-periodic burning mode, and a purely transient burning condition. In the quasi-periodic burning mode, the time scale of the oscillations is shown to affect the chemistry by providing an observed extinction reignition process associated with the unsteady fuel flux into the flame sheet. For the purely transient burning process radiation extinction occurs for certain soot loadings, initial fuel element sizes, and environmental temperatures. | Abstract Within the framework of perturbative QCD I show that the high energy factorization formula for jets observables resumming to all orders the leading log(s) can be extended to next-to-leading log(s) approximation. In addition, I provide the last missing factor of such a formula, namely the NL correction to the jet-production vertex. This makes it possible to perform accurate analyses of high energy processes like dijets at hadron-hadron colliders as well as forward jets at lepton-hadron colliders in a framework that is now consistent with both DGLAP evolution and BFKL evolution, providing a quantitative tool for exploring QCD in the high energy regime. | eng_Latn | 26,918 |
INTERNAL CONVERSION PAIRS IN NEUTRAL PION DECAY | Twenty-seven events of charge-exchange scattering with subsequent decay pi /sup 0/ yields e/sup -/ + e/sup -/ + gamma were recorded in th e hydrogen- filled diffusion cloud chamber placed in a magetic field and exposed to 128 and 162 Mev negative pion beams. A probability of this decay with respect to the usual decay was found. The results of the measurements of momenta and angles of electron-positron pairs are presented. The energy characteristics of pairs and angular distributions experimentally found are in good agreement with the theoretical ones. (auth) | The article investigates structural change among the four-digit (SIC) industries of the US manufacturing sector during 1958–1996 and its relation to productivity growth within a distribution dynamics framework. Focus is on the transition density of the Markov process that characterizes the value-added shares of the industries. This transition density is estimated nonparametrically as well as by maximum likelihood, in which case the functional form of the density is motivated by a search theoretic model. The nonparametric fit and the maximum likelihood fit show striking similarities. The relation of structural change to a measure of total factor productivity change is tested by quantile regression and appears to be significantly positive throughout. Copyright 2008 , Oxford University Press. | yue_Hant | 26,919 |
Enhanced vacuum Rabi splitting and double dark states in a composite atom-cavity system | The transmission spectrum of four-level atoms in a cavity is calculated. It is shown that the four separate peaks associated with normal mode splitting and intra-cavity double dark states can be observed simultaneously. The position and intensity of the four peaks can be controlled by the intensity of the third interacting light. Therefore, the enhancement of normal mode splitting by a third coupling light of the intra-cavity four-level atoms is developed. | We discuss some recent phenomenological models for strong interactions based on the idea of gauge/string duality. A very good estimate for hadronic masses can be found by placing an infrared cut off in AdS space. Considering static strings in this geometry one can also reproduce the phenomenological Cornell potential for a quark anti-quark potential at zero temperature. Placing static strings in an AdS Schwarzschild space with an infrared cut off one finds a transition from a confining to a deconfining phase at some critical horizon radius (associated with temperature). | eng_Latn | 26,920 |
Explanation of the Rb-Rc discrepancy using new physics. | The experimental values of Rb and Rc are the only data which do not seem to agree with standard model predictions. Although it is still premature to draw any definite conclusions, it is timely to look for new physics which could explain the excess in Rb and deficit in Rc . We investigate this problem in a simple extension of the standard model, where a charge 12/3 isosinglet quark is added to the standard spectrum. Upon the further introduction of an extra scalar doublet, one finds a solution with interesting consequences. @S0556-2821~96!00515-2# | 4 pages.-- PACS numbers: 05.45.Xt, 87.10.+e.-- ArXiv pre-print: http://arxiv.org/abs/nlin.CD/0512009.-- Final full-text version of the paper available at: http://dx.doi.org/10.1103/PhysRevE.73.055202. | eng_Latn | 26,921 |
Pion-skyrmion scattering: collective coordinates at work, SLACPUB 3703, published | It is argued that the Skryme model, and more generally, the picture of the nucleon as a chiral soliton, can give a qualitatively correct picture of pion-nucleon scattering, considering both group-theoretic and more scheme-dependent results. The properties of the nucleon and its excited states in large-N quantum chromodynamics are discussed qualitatively. Then the pion-nucleon S-matrix is reduced. It is found that the model succeeds at the first level of calculation in producing many of the features of pion-nucleon scattering which are revealed by experiment, but that many aspects of the description need to be better understood, including the treatment of nonleading corrections near threshold and the inclusion of inelastic channels. 22 refs., 8 figs. (LEW) | Lattice QCD can give direct information on OZI-violating contributions to mesons. Here we explore the contributions that split flavour singlet and non-singlet meson masses. I discuss in detail the spectrum and decays for scalar mesons (ie including glueball effects). I also review the status of hybrid mesons and their decays. | eng_Latn | 26,922 |
A Note on the Changes of the Maximum of Ionization of the F1 Layer Associated with the Sunspot Activity | AbstractThe ionospheric F1 layer, whose behaviour conforms to the standard theory during low and moderate solar activity, shows considerable departure from it when the solar activity is very high. The simple relationship which has been shown to exist between foF1 and the mean Zurich sunspot number (Ratcliffe et al., 1956) no longer holds at very high sunspot numbers that were observed during the current solar epoch. Also, foF1 shows anomalous behaviour with respect to season and geographic latitude, similar to that of the F2 layer, at very high solar activity. | We calculate the threshold T-matrices of kaon-nucleon and antikaon-nucleon scattering to one loop order in SU(3) heavy baryon chiral perturbation theory. To that order the complex-valued isospin-1 $\bar KN$ threshold T-matrix can be successfully predicted from the isospin-0 and 1 $KN$ threshold T-matrices. As expected perturbation theory fails to explain the isospin-0 $\bar KN$ threshold T-matrix which is completely dominated by the nearby subthreshold $\Lambda^*(1405)$-resonance. Cancelations of large terms of second and third chiral order are observed as they seem to be typical for SU(3) baryon chiral perturbation theory calculations. We also give the kaon and eta loop corrections to the $\pi N$ scattering lengths and we investigate $\pi\Lambda$ scattering to one-loop order. The second order s-wave low-energy constants are all of natural size and do not exceed 1 GeV$^{-1}$ in magnitude. | eng_Latn | 26,923 |
Anisotropic saturation of the electron spin resonance in the photo-excited triplet state of pyrene-d-10 | Electron spin saturation measurements have been performed on the optically excited triplet state of pyrene-d-10 in biphenyl. An order of magnitude anisotropy is found in the amount of power needed to saturate the spin resonance as the molecule is rotated in the external magnetic field. Relaxation times have been inferred at room temperature and the anisotropy is found to be consistent with that predicted by the modulation of the electron spin-spin interaction. For pyrene-d-10 in biphenyl: | We calculate the chiral condensate of QCD at infinite coupling as a function of the number of fundamental fermion flavours using a lattice diagrammatic approach inspired by recent work of Tomboulis, and other work from the 80's. We outline the approach where the diagrams are formed by combining a truncated number of sub-diagram types in all possible ways. Our results show evidence of convergence and agreement with simulation results at small Nf. However, contrary to recent simulation results, we do not observe a transition at a critical value of Nf. We further present preliminary results for the chiral condensate of QCD with symmetric or adjoint representation fermions at infinite coupling as a function of Nf for Nc = 3. In general, there are sources of error in this approach associated with miscounting of overlapping diagrams, and over-counting of diagrams due to symmetries. These are further elaborated upon in a longer paper. | eng_Latn | 26,924 |
A definition of the single-nucleon potential | Abstract The definition is the familiar one which regards a single-particle energy as an average of actual energy levels weighted with spectroscopic factors. It is shown to be related to the shorttime behavior of the single-nucleon propagator. This leads to a Feynman expansion which is then compared with the expansion of the exact energies, related to the long-time behavior. The first expansion contains only a small fraction of the diagrams occurring in the second, namely those diagrams in which the two external lines issue from a common two-body vertex. This particular definition of the single-nucleon potential is capable of playing a central role in comparisons between BHF calculations and experiment. Short-range correlations can be eliminated and present no difficulty. Finally, a similar time-development leads to the Feynman expansion of the width of the single-nucleon strength distribution. | This paper presents the recent development of the pulsed power technology based on inductive energy storage (including Superconducting Magnetic Energy Storage, SMES) and its opening switch. It also introduces several circuit topologies with power electronics/superconducting opening switch. | eng_Latn | 26,925 |
Ionization radii of compressed atoms | The compression of all atoms has been modelled by changing the free-atom boundary condition obeyed by electronic wavefunctions, from r [graphic omitted] ∞, ψ(r)= 0 to r [graphic omitted] ro, ψ(r)= 0, ro < ∞, in numerical Hartree–Fock–Slater calculations of electronic energy levels. As ro decreases, energy levels increase uniformly and by transferring the excess energy, an electron escapes from the valence shell when compression reaches a critical value of ro, characteristic of each atom. These ionization radii display remarkable periodicity, commensurate with the known chemistry of the elements, and introduce a new fundamental theoretical parameter that could serve to quantify chemical reactivity. Insofar as the compression of atomic wavefunctions occurs within crowded environments that lead to chemical interactions, ionization radii provide a more realistic index of the chemical properties of atoms in the bulk, than ionization energies, which are more appropriate in spectroscopic analyses of free atoms. | In this talk I summarize recent findings around the description of axial vector mesons as dynamically generated states from the interaction of pseudoscalar mesons and vector mesons, dedicating some attention to the two $K_1(1270)$ states. Then I review the generation of open and hidden charm scalar and axial states, and how some recent experiment supports the existence of the new hidden charm scalar state predicted. I present recent results showing that the low lying $1/2^+$ baryon resonances for S=-1 can be obtained as bound states or resonances of two mesons and one baryon in coupled channels. Then show the differences with the S=0 case, where the $N^*(1710)$ appears also dynamically generated from the two pion one nucleon system, but the $N^*(1440)$ does not appear, indicating a more complex structure of the Roper resonance. Finally I shall show how the state X(2175), recently discovered at BABAR and BES, appears naturally as a resonance of the $\phi K \bar{K}$ system. | eng_Latn | 26,926 |
Yun Yang in Qin and Han Dynasty | Yun Yang Lines in these places—the River of Jing to the south,Zhi Dao to the north,the middle part of Shaanxi to the east and mountains to the west.It is an ancient city germinated in legend era but got great prosperity in Qin and Han Dynasty.In order to restore the original shape of Yun Yang,this paper centers on several character Btizs present- ed in Qin and Han Dynasty. | In Ref. [1] we proposed a model for Heterotic $F$-theory duality with Wilson line symmetry-breaking and a $4+1$ split of the $F$-theory spectral divisor. One goal of this note is to call attention to the existence of right-handed neutrinos in our $F$-theory model. As pointed out in Section 4 of Ref. [2] such existence may be evidence for the $U\left(1\right)_{X}$-symmetry that remains after the Higgsing of $E_{8}$ via \[ E_{8}\Rightarrow SU\left(5\right)_{gauge}\oplus\left[SU\left(4\right)\oplus U\left(1\right)_{X}\right]_{Higgs} \] occasioned by the $4+1$ split of the spectral divisor. In addition, as a result of the $\mathbb{Z}_{2}$-action that supports the Wilson line we argue that the $U\left(1\right)_{X}$-symmetry is, in fact, broken to $\mathbb{Z}_{2}$-matter parity. Finally we identify co-dimension $3$ singularities which determine Yukawa couplings for the MSSM matter fields. | eng_Latn | 26,927 |
Generalized Canonical Form of a Multi-Time Dynamical Theory and Quantization | A generalized canonical form of multi-time dynamical theories is proposed. This form is a starting point for a modified canonical quantization procedure of theories based on a quantum version of the action principle. As an example, the Fokker theory of a direct electromagnetic interaction of charges is considered. | Recently, both ATLAS and CMS collaborations report an excess at 750GeV in the diphoton invariant mass spectrum at 13TeV LHC. If it is a new scalar produced via loop induced gluon-gluon fusion process, it is important to know what is the particle in the loop. In this work, we investigate the possibility of determine the fraction of the contribution from the standard model top-quark in the loop. | eng_Latn | 26,928 |
Artists Ma Desheng, Wang Keping, Huang Rui, Li Shuang, Zhong Acheng, Ai Weiwei and Qu Leilei are associated with which avant-garde art group? | Ai Wei Wei @ 798district.com 798district.com >> 798 Artists >> Art >> Ai Wei Wei Ai Wei Wei Ai Weiwei, (born 1957, Beijing) is a leading Chinese artist, curator, architectural designer, cultural and social commentator and activist. Ai is known for the design of the Beijing National Stadium, more commonly known as the "Bird's Nest", the main stadium of the 2008 Olympic Games in Beijing. Beginning with the 2008 Sichuan earthquake, Ai has emerged as one of China's most influential bloggers and social activists; he is known for his tongue-in-cheek and sometimes vulgar social commentary, and has had frequent run-ins with Chinese authorities. He was particularly focused at exposing an alleged corruption scandal in the construction of Sichuan schools that collapsed during the earthquake. Born in Beijing, his father was Chinese poet Ai Qing, who was denounced during the Cultural Revolution and sent off to a labor camp in Xinjiang with his wife, Gao Ying. Ai Weiwei also spent five years there. Ai Weiwei is married to artist Lu Qing. Ai Weiwei is represented by Galerie Urs Meile, Beijing-Lucerne. Education In 1978, Ai enrolled in the Beijing Film Academy and attended school with Chinese directors Chen Kaige and Zhang Yimou. In 1978, he was one of the founders of the early avant garde art group the "Stars", together with Ma Desheng, Wang Keping, Huang Rui, Li Shuang, Zhong Acheng and Qu Leilei. In China the group subsequently disbanded in 1983. Yet Ai Weiwei participated in regular Stars group shows, The Stars: Ten Years, 1989 (Hanart Gallery, Hong-Hong and Taipei), and a retrospective exhibition in Beijing in 2007: Origin Point (Today Art Museum, Beijing). Influences From 1981 to 1993, he lived in the United States, mostly in New York, doing performance art and creating conceptual art by altering readymade objects. While in New York, he studied at Parsons School of Design.. In 1987 he took part in the founding of The Chinese United Overseas Artists Association, along with Li Shuang, Qu Leilei, Zhang Hongtu. In 1993, Ai returned to China because his father became ill. Back in Beijing, he helped establish the experimental artists' East Village and published a series of three books about this new generation of artists: Black Cover Book (1994), White Cover Book (1995), and Gray Cover Book (1997). In 2000, he co-curated the notorious art exhibition "Fuck Off" with curator Feng Boyi in Shanghai, China. In 2000, Ai Weiwei moved to Caochangdi where he built a compound of houses and opened his studio REAL/FAKE. In 2006, Ai Weiwei and HHF Architects designed a private residence in Columbia County, New York. According to the New York Times, the house was completed in 2008 and is "extraordinarily refined". Ai was the artistic consultant for design, collaborating with the Swiss firm Herzog & de Meuron, for the Beijing National Stadium for the 2008 Summer Olympics, also known as the "Bird's Nest." Although ignored by the Chinese media, he has voiced his anti-Olympics views. He later distanced himself from the project, saying, "I've already forgotten about it. I turn down all the demands to have photographs with it," saying it is part of a "pretend smile" of bad taste. In August 2007 he also accused those choreographing the Olympic opening ceremony, including Steven Spielberg and Zhang Yimou, of failing to live up to their responsibility as artists. Ai said "It's disgusting. I don't like anyone who shamelessly abuses their profession, who makes no moral judgment." While being asked why he participated in the designing of the Bird's Nest, Ai replied "I did it because I love design." | CERN finds four new X particles – how big a deal is this? | Cosmos Save to Pocket Email link Print article Facebook Twitter Reddit Email link Print article CERN finds four new X particles – how big a deal is this? Physicists at CERN have discovered a family of new 'exotic' particles. Cathal O’Connell assesses what it means. The LHCb particle detector magnet. CERN/SPL CERN/SPL What’s just happened? Physicists at CERN have discovered four new “tetraquark” particles – unusual arrangements of four fundamental particles called quarks. The new particles are highly unstable, decaying almost immediately into other particles. These are not new fundamental particles heralding a new era of physics (like the unexpected new one recently hinted at ) but rather are new combinations of previously known particles in the standard model of particle physics (See the Cosmos primer on particle physics for an explanation). The new particles are called “exotic” because they are made of four quarks. Quarks usually group together in twos and threes. Physicists at the Large Hadron Collider beauty (LHCb) collaboration made the discoveries by monitoring the decays of B mesons (so-called beauty particles) formed in CERN’s Large Hadron Collider. The results have not yet been peer reviewed, but have been published in two papers ( here and here ) on the arXiv.org pre-print server, where physicists share their results prior to peer review. Tetra-what? At the deepest level, we are all made of quarks. Quarks are the fundamental particles that gang together to form protons and neutrons. They come in six “flavours”: up, down, top, bottom, strange and charm. Quarks are most stable in groups of three. And so the physicist who proposed them, Murray Gell-Mann, coined their name from a quote in James Joyce’s novel Finnegan’s Wake, in which a publican dreams of a drunken seagull ordering beer by demanding “three quarks for Muster Mark”, instead of “three quarts for Mister Mark!” But in the past two years, scientists have discovered that quarks can sometimes form other, temporary alliances – a bit like politicians making an unlikely crossbench deal. In 2014 scientists at CERN discovered the first four-quark particle, called a tetraquark. Last year, the same team also discovered a five-member variety . None of these particles exist for more than a fraction of a second before decaying. Discovery, or confirmation? One of the new tetraquarks had been glimpsed before, though not with enough certainty to be called a “discovery”. Now LHCb has confirmed its existence with a significant of over five sigma (meaning there’s a less than 1 in 3.5 million chance the signal is a chance fluctuation in the data). The placeholder name of the particle, X(4140), seems like something off a car number plate, but actually comes from its mass measured in megaelectronvolts (4140 MeV). This makes it about four times heavier than the proton. The other three particles are dubbed with equally catchy names, X(4274), X(4500) and X(4700). None of these three had been detected before – so they are new discoveries. What are they made of? All four are made of the same gang of quarks (one charm, one anti-charm, one strange and one anti-strange) but differ in the energy states of their constituents. In this sense, the four are really just versions of the same particle. Besides their masses, the physicists were able to measure each particle’s quantum numbers, which describe their subatomic properties. How big of a deal is this? The new particles are interesting because they’re the first four-quark particles found that are made of only the heavy quarks (strange and charm). Studying them could help us understand how these big quarks interact. But because these tetraquark particles are transient, they likely have a very minor role in the makeup of the universe. With LHC now revved up to a collision energy of 13 TeV, and generating one billion proton collisions per second. That unprecedented deluge of data can only lead to more quirks and varieties of quarks in future. Expect more tetraquarks. | eng_Latn | 26,929 |
In particle physics there are six 'flavours' of quarks; up, down, top and bottom are four of them, name either of the other two. | CERN finds four new X particles – how big a deal is this? | Cosmos Save to Pocket Email link Print article Facebook Twitter Reddit Email link Print article CERN finds four new X particles – how big a deal is this? Physicists at CERN have discovered a family of new 'exotic' particles. Cathal O’Connell assesses what it means. The LHCb particle detector magnet. CERN/SPL CERN/SPL What’s just happened? Physicists at CERN have discovered four new “tetraquark” particles – unusual arrangements of four fundamental particles called quarks. The new particles are highly unstable, decaying almost immediately into other particles. These are not new fundamental particles heralding a new era of physics (like the unexpected new one recently hinted at ) but rather are new combinations of previously known particles in the standard model of particle physics (See the Cosmos primer on particle physics for an explanation). The new particles are called “exotic” because they are made of four quarks. Quarks usually group together in twos and threes. Physicists at the Large Hadron Collider beauty (LHCb) collaboration made the discoveries by monitoring the decays of B mesons (so-called beauty particles) formed in CERN’s Large Hadron Collider. The results have not yet been peer reviewed, but have been published in two papers ( here and here ) on the arXiv.org pre-print server, where physicists share their results prior to peer review. Tetra-what? At the deepest level, we are all made of quarks. Quarks are the fundamental particles that gang together to form protons and neutrons. They come in six “flavours”: up, down, top, bottom, strange and charm. Quarks are most stable in groups of three. And so the physicist who proposed them, Murray Gell-Mann, coined their name from a quote in James Joyce’s novel Finnegan’s Wake, in which a publican dreams of a drunken seagull ordering beer by demanding “three quarks for Muster Mark”, instead of “three quarts for Mister Mark!” But in the past two years, scientists have discovered that quarks can sometimes form other, temporary alliances – a bit like politicians making an unlikely crossbench deal. In 2014 scientists at CERN discovered the first four-quark particle, called a tetraquark. Last year, the same team also discovered a five-member variety . None of these particles exist for more than a fraction of a second before decaying. Discovery, or confirmation? One of the new tetraquarks had been glimpsed before, though not with enough certainty to be called a “discovery”. Now LHCb has confirmed its existence with a significant of over five sigma (meaning there’s a less than 1 in 3.5 million chance the signal is a chance fluctuation in the data). The placeholder name of the particle, X(4140), seems like something off a car number plate, but actually comes from its mass measured in megaelectronvolts (4140 MeV). This makes it about four times heavier than the proton. The other three particles are dubbed with equally catchy names, X(4274), X(4500) and X(4700). None of these three had been detected before – so they are new discoveries. What are they made of? All four are made of the same gang of quarks (one charm, one anti-charm, one strange and one anti-strange) but differ in the energy states of their constituents. In this sense, the four are really just versions of the same particle. Besides their masses, the physicists were able to measure each particle’s quantum numbers, which describe their subatomic properties. How big of a deal is this? The new particles are interesting because they’re the first four-quark particles found that are made of only the heavy quarks (strange and charm). Studying them could help us understand how these big quarks interact. But because these tetraquark particles are transient, they likely have a very minor role in the makeup of the universe. With LHC now revved up to a collision energy of 13 TeV, and generating one billion proton collisions per second. That unprecedented deluge of data can only lead to more quirks and varieties of quarks in future. Expect more tetraquarks. | Corridors of Power: C. P. Snow: Amazon.com: Books Corridors of Power Customers Who Viewed This Item Also Viewed Page 1 of 1 Start over Page 1 of 1 This shopping feature will continue to load items. In order to navigate out of this carousel please use your heading shortcut key to navigate to the next or previous heading. Next Special Offers and Product Promotions Don't have a Kindle? Get your Kindle here , or download a FREE Kindle Reading App . New York Times best sellers Browse the New York Times best sellers in popular categories like Fiction, Nonfiction, Picture Books and more. See more Product Details Amazon Best Sellers Rank: #10,698,843 in Books ( See Top 100 in Books ) Customer Reviews By C. L Wilson on March 8, 2006 Apparently, it was Snow who coined the phrase "corridors of power" in an earlier book. This one is all about English politics, and the machinations that go on in trying to change policy. I suspect it was far more riveting to an English reader who knows more about the workings of Parliament than I do. Rather dry, and involved, with many, many characters. Only in the last fifty pages or so is there any semblance of suspense. As usual, Lewis Eliot is the narrator and at the heart of matters. Exactly how he got to be such a confidante of Roger Quaife, who seems to be a Minister in another department, I never could figure out. Snow, I suspect, lived these times and questions, but perhaps he was too close to see that his reader might need a little more explanation. Quaife is trying to disengage England from the nuclear arms race, a thoroughly admirable position, but one which would have required Parliament to own up to the fact that England was no longer a super power, a hard pill to swallow indeed. Many times, throughout the book, one or another character expresses the thought that no man can really do much of anything, that government will go on in its own way no matter who is at the helm. If you like to read about power and politics, all the weavings in and out, and subplots, the goings on behind the top, this book would probably rate high with you. I do not think it Snow's best. Once again, he is too detached. Too close to the heartbeat of things. On rereading this six years later, I see that like "The Affair", and "The Conscience of the Rich", this one too is about reputation and honor and conscience, very much so. A running theme with Snow apparently. And yet another one that is not about Lewis Eliot at all, but about other characters and arenas of life. I do not disagree with my earlier review, but now I see the distance Snow has chosen. In "The Affair", the plot revolved around Howard and Cambridge, in "Conscience", about the March family, and the world of the truly wealthy, and now, the 3rd, about Roger Quaife and the workings of Parliament. Eliot, as a character, is really only the narrator of all the events and - way too much so - the dissector of all the characters' natures, reasons for acting, etc. That got a bit much. Too intricate, far too much delving into the various psyches. But his emphasis on the nature of the times, and the questions and events being too much for any one person to alter, certainly rings true today also. How we all feel helpless to change the way history is being played out. It would seem we are the product of our times; not that time is a product of our actions. Things just march inexorably on. Relentless. Anthony Hopkins played Quaife in the dismal BBC series, because Snow kept referring to him as Pierre, and Hopkins played Pierre in the marvelous "War and Peace". By Timothy J Hurst on May 31, 2015 Format: Kindle Edition|Verified Purchase If you haven't read any of the Strangers and Brothers series, you shouldn't start with this book, because they're sequential, and not everyone's cup of tea. I suggest you try GEORGE PASSANT first, the first one that C.P.Snow wrote, although chronologically second. You'll know by the end of the second chapter whether it's for you. I really like the series - it follows an Englishman, Lewis Elliot, from his chil | eng_Latn | 26,930 |
A graviton is a term in? | Graviton | Define Graviton at Dictionary.com graviton noun, Physics. 1. the theoretical quantum of gravitation, usually assumed to be an elementary particle that is its own antiparticle and that has zero rest mass and charge and a spin of two. Expand British Dictionary definitions for graviton Expand noun 1. a postulated quantum of gravitational energy, usually considered to be a particle with zero charge and rest mass and a spin of 2 Compare photon Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012 graviton (grāv'ĭ-tŏn') A hypothetical particle postulated in supergravity theory to be the quantum of gravitational interaction, mediating the gravitational force. Like all force carriers, the graviton is a boson. It is presumed to have an indefinitely long lifetime, zero electric charge, a spin of 2, and zero rest mass (thus travelling at the speed of light). The graviton has never been detected. See also supersymmetry . See Table at subatomic particle . The American Heritage® Science Dictionary Copyright © 2002. Published by Houghton Mifflin. All rights reserved. | Girton College - Girton Community Girton Community CamCORS Contacts Girton Community Girton College is part of the University of Cambridge. It is a world-class higher education institution, comprising a vibrant community of undergraduate and graduate students, academic Fellows and professional administrative and support staff. This section contains information primarily for College members. Some sections are visible only by those who have logged-in using their Raven Password. | eng_Latn | 26,931 |
Like all quarks , the top quark is an elementary fermion with spin-1 ⁄ 2 , and experiences all four fundamental interactions : gravitation , electromagnetism , weak interactions , and strong interactions . | Top quarks interact with all four of the fundamental forces , which are gravity , electromagnetism , strong force , and weak force . | The FSF maintains a list of `` high priority projects '' where the Foundation says that `` there is a vital need to draw the free software community 's attention '' . | eng_Latn | 26,932 |
Strange quarks are found in subatomic particles called hadrons . | Strange quarks can be found in particles such as kaons and some hyperons . | A Hurricane Hunter scouting flight reported hail , which is unusual for tropical cyclones . | eng_Latn | 26,933 |
What is the difference between partition function for two-boson system and two-fermion system? | I have two atoms, both of which are either bosons or fermions, with four allowed energy states: $E_1 = 0$, $E_2 = E$, $E_3 = 2E$, with degeneracies 1, 1, 2 respectively. What's the difference between the partition functions of a pair of two bosons and that of a pair of two fermions? | I have two atoms, both of which are either bosons or fermions, with four allowed energy states: $E_1 = 0$, $E_2 = E$, $E_3 = 2E$, with degeneracies 1, 1, 2 respectively. What's the difference between the partition functions of a pair of two bosons and that of a pair of two fermions? | eng_Latn | 26,934 |
The image shows experimental data for the ratio of cross sections $$R=\frac{\sigma(e^+e^-\rightarrow\text{hadrons})}{\sigma(e^+e^-\rightarrow\mu^+\mu^-)}.$$ I am wondering why $R$ is so large for the $Z$ resonance. I thought that it would only depend on the branching ratios of the $Z$ decay into hadrons and muons, but this gives $R\approx 20$ which is much too small. | Below is experimental data for the ratio $$R=\frac{\sigma(e^+e^-\rightarrow hadrons)}{\sigma(e^+e^-\rightarrow\mu^+\mu^-)}$$ as a function of the centre of mass energy $\sqrt s$. I am interested in the peak at around $100GeV$ which corresponds to the resonance of the $Z^0$ boson. There are two ways of looking at this that I have in mind: We can effectively ignore the electromagnetic process around this energy, and so each process should have it's own Breit-Wigner peak centred on the mass energy of the $Z^0$. The ratio of these is just a constant. Thinking in terms of Feynman rules and again ignoring the electromagnetic process around this region, each process has the same propagator and vertex factors (roughly - ignore quark mixing) and there are some extra factors due to different quarks being possible and colour degeneracy, but still the ratio should be a constant (one possible issue here is interference between Feynman diagrams which I have neglected?). So my question is why does the peak exist in the data? | Prove that there is no retraction (i.e. continuous function constant on the codomain) $r: M \rightarrow S^1 = \partial M$ where $M$ is the Möbius strip. I've tried to find a contradiction using $r_*$ homomorphism between the fundamental groups, but they are both $\mathbb{Z}$ and nothing seems to go wrong... | eng_Latn | 26,935 |
Can there be a two-neutron bound state? | Why are the dineutron and diproton unbound? | A fiber bundle over Euclidean space is trivial. | eng_Latn | 26,936 |
The neutral pion π0 is a combination of an up quark with an anti-up quark or a down quark with an anti-down quark . | π0 can be formed with one up quark and an up antiquark , or one down quark and one down antiquark . | ) is a French aeronautical non-profit organization created in 1927 in order to `` group , in a close community all those who belong , by their profession , to the civil aviation , and participate in the development of the national aeronautics , in conjunction with the public authorities , the manufacturers , the airlines and the professionals unions '' . | eng_Latn | 26,937 |
Why is this decay process allowed? | How does Delta baryon decay conserve angular momentum? | Why is the decay of a neutral rho meson into two neutral pions forbidden? | eng_Latn | 26,938 |
Does a black hole singularity compress mass back into energy? I was watching this which made the case that mass is just a form of bound energy. Essentially massless particles are confined in a small space giving particles the illusion of mass. Since the heat and pressure inside a black hole is essentially infinite, does that mean that matter can't hold its form at the singularity and therefore reverts back into energy via $E=mc^2$? Wouldn't the converse (elementary particles keep their mass) lead to infinities (which are impossible) as the black hole tries to infinitely compress particles at the singularity? Should the singularity be instead described as a peak in the energy field of the Universe, instead of a physical object? | Where does matter go after reaching singularity in uncharged black holes? I am a layman in physics and just read about black holes on the internet. I read that matter encounters geodesic incompleteness in the singularity in an uncharged black hole. I heard an analogy of geodesic incompleteness as a straight line on a paper reach a hole on the paper, so it cannot continue. But in this analogy, isn't the straight line possible to continue into 3D (continue down the paper)? So, if matter reaches the singularity, is it possible too (to reach another dimension)? I also heard that the matter is annihilated when reaching the singularity, does it mean it disappear from this world, and violates conservation of energy? | What happens to matter in a standard model with zero Higgs VEV? Suppose you reset the parameters of the standard model so that the Higgs field average value is zero in the vacuum, what would happen to standard matter? If the fundamental fermions go from a finite to a zero rest mass, I'm pretty sure that the electrons would fly away from nuclei at the speed of light, leaving positively charged nuclei trying to get away from each other. Looking at the solution for the Hydrogen atom, I don't see how it would be possible to have atoms with zero rest mass electrons. What happens to protons and neutrons? Since only a very small part of the mass of protons and neutrons is the rest mass of the quarks, and since they're flying around in there at relativistic speeds already, and since the nuclear force is so much stronger than the electrical force with an incredible aversion to naked color, would protons and neutrons remain bound assemblages of quarks and virtual gluons? Would they get a little larger? A little less massive? What would happen to nuclei? Would they stay together? If the protons and neutrons hold together and their properties change only some, then I might expect the same of nuclei. Different stable isotopes, different sizes, and different masses, but I would expect there would still be nuclei. Also the W and Z particles go to zero rest mass. What does that do to the electroweak interactions? Does that affect normal stable matter (outside of nuclear decay modes)? Is the weak force no longer weak? What happens to the forces overall? | eng_Latn | 26,939 |
Distance between particles in pair annihilation (or any other matter antimatter collision) | How close does a particle-antiparticle pair need to be for annihilation to happen? | How close does a particle-antiparticle pair need to be for annihilation to happen? | eng_Latn | 26,940 |
Why did the Crown allow giving Highgarden to Bronn? According to about the ending of Game of Thrones, Bronn gets Highgarden: Kingdom of the Reach - Unknown Ruler: Bronn; Highgarden is part of the six kingdoms; Bronn was given highgarden as payment of the Lannister debts. This was of course part of the deal the Lannister boys made with Bronn so he wouldn't kill them. The remaining Lannister does not seem to have the power to give away other kingdoms. It seems very likely that King Bran has agreed with Bronn getting Highgarden? Is this somehow explained in the series? In particular, Bronn seems a bad choice because he does whatever monetary incentives are in play. If anyone, Bran would know that Bronn just does what whomever pays the most tells him to do This is not a duplicate of , which asks about Tyrion's power. I am asking about why the King agreed to this, or if that's not clear from the series. | Did Tyrion even have the authority to do this? In Game of Thrones S08E04 (The Last of the Starks) when Tyrion and Jaime are confronted by Bronn, Tyrion attempts to evade poetic justice by offering Bronn Highgarden. Was it even within Tyrion's power to give away Highgarden? Follow up question: Why would Bronn even risk waiting around to see how things play out? Based on his demeanor during that conversation, he seemed pretty pissed that all he has to show for serving the Lannisters is a lousy title. So, why wouldn't he just take bird in hand and collect the reward from Cersei instead of risking Tyrion dying before all of this is over? I mean, Tyrion even mentioned to him that all of this means nothing until they [the North] take over King's Landing, but it didn't really seem to faze Bronn. | What do the supercharges in extended supersymmetry do? What do the supercharges in do? In ${\cal N}=1$ supersymmetry there are a certain number of fermions and and equal number of bosons. You can transform all fermions to the bosons (and vice versa) in a 1 to 1 fashion using a single supercharge, $Q$. So what happens when you have, for example, ${\cal N}=2$ supersymmetry with 8 supercharges? Since $Q$ is a generator of supersymmetry transformations, is it a linear combination of these supercharges that act on the particles? In which case could one particle be acted on by two separate linear combinations of $Q$? Or is it strictly one linear combination of $Q$ per fermion/boson? Also, what does ${\cal N}$ mean physically? What difference does ${\cal N}=2$ have to ${\cal N}=1$ other than more supercharges? Or is that the only difference between the two theories? | eng_Latn | 26,941 |
Color is a property of these fundamental particles that come in strange & charm types | Quarks - HyperPhysics There was a recent claim of observation of particles with five quarks ... Charm ... These masses represent a strong departure from earlier approaches which ... The presence of a strange quark in a particle is denoted by a quantum number S=-1. ... example of the need for the property called "color" in describing particles. | James Chadwick - Biography, Facts and Pictures - Famous Scientists James Chadwick discovered the neutron in 1932 and was awarded the ... It had been a tough three years financially Chadwick always went without ... After graduating, Chadwick continued to work in Rutherford's laboratory until, ... In fact, Chadwick at this time did not believe he had discovered a new elementary particle. | eng_Latn | 26,942 |
Measurement collapsing wave functions I'm sure variations on this come up a lot, but I was specifically interested in a response to a claim made by a particular article: The article is aiming to disprove the idea that an 'observer' collapsing a wave function has anything to do with consciousness or human observers. At one point it argues that the reason an electron in the double slit experiment has its wave function collapsed when detected before entering one slit or the other is due to the photons fired at it to detect its position having momentum and physically interacting with it. The author uses the analogy of tennis balls being fired into a dark room and using a tennis racquet to detect them - the method of detection causes a change in their behaviour. Now in this instance that's all well and good, but firing photons is not the only means of detecting something. In the Schrödinger's cat thought experiment, for instance, a Geiger counter is used. As far as I understand it, these simply detect passively rather than firing out photons with momentum. I know many people disagree with the wave function collapse theory and prefer decoherence (which I'm still wrapping my head around) but I'm interested to know if this is something that's explained within collapse theory or if it's something that's seen as disproving it. | In the double-slit experiment of electrons (observed by photons), is it correct to say the collapse is caused by the momentum of the photons? I'm working off the article, . I think it's well-written, but I'm not convinced about this part: So what is causing the change in the particle’s behaviour? In the example given above, when electrons are fired at a fluorescent screen, when we bombard the electrons with photons the interaction changes the state of the system catastrophically as, despite lacking mass, photons do carry momentum. Here the author strongly implicates the momentum of photons as being responsible for the collapse. But is that correct to say? I have read that the verified that obscuring which-way information restores wave-like behavior. So it feels to me it's more about some "outer" state (perhaps well-characterized as "information") that we don't yet understand that collapses the system, not per se the photon-electron interaction. Or am I wrong, and in fact for example, the process of obscuring in the quantum eraser experiments somehow "undoes" the photon-electron interaction or restores the quantum state through another interaction? | What role does "spontaneously symmetry breaking" played in the "Higgs Mechanism"? In talking about Higgs mechanism, the first part is always some introduction to the concept of spontaneously symmetry breaking (SSB), some people saying that Higgs mechanism is the results of SSB of local gauge symmetry, some people says that we can formulate Higgs mechanism in a gauge invariant way, some people also says that we need only a non-zero vaccum expectation value... I am confused about this different or maybe same point of views. In this post: , the most highly voted answer, I still can't feel how SSB worked in Higgs mechanism. It seem that the validity of last part, the appearance of a mass term for $A$, is guaranteed if we have a non-zero equilibrium value $\phi_0$ to expand around. I do not see that the requirement that the phase of the field $\phi$ need to be fixed at some particular value to generate mass term. Thus it seems to me it is not true that SSB is really indispensable for Higgs mechanism. To put it simply: The spontanously breaking of what is attributed to Higgs mechanism? local gauge symmetry global symmetry, since breaking of a "gauge symmetry" should not have any effect on physics. In higgs mechanism, the really broken symmetry is a global one. Mathematically, it is similar in looking as fixing a gauge, but one should not think it as a spontanously breakdown of local gauge symmetry. other. Is SSB really indispensable for Higgs mechanism? yes, Higgs mechanism is relied on the SSB of some symmetry (above question), the other approches of description eventually has spontanously broke some symmetry. No, the SSB is just one way to describe Higgs mechanism (or even not a complete way), what is really need is the non-zero vaccum expectation value, for example in the linked post the requirement for the mass term to occur is to have some non-zero expectation value of $\phi$ to expand around, we do not need the phase of the field to be fixed, thus the symmetry is not broken. Other. some reference materials: States that SSB of local gauge symmetry is impossible. in the abstract states that: gauge symmetries merely reflect a redundancy in the state description and therefore the spontaneous breaking can not be an essential ingredient. Indeed, as already shown by Higgs and Kibble, the mechanism can be explained in terms of gauge invariant variables, without invoking spontaneous symmetry breaking In the introduction it says: In particular, we emphasize that global U(1) phase rotation symmetry, and not gauge symmetry, is spontaneously violated, and show that the BCS wave function is, contrary to claims in the literature, fully gauge invariant | eng_Latn | 26,943 |
I am wondering if the masslessness of photons is due to the local gauge invariance of $u(1)$-gauge fields. The reason why I consider about this question is that I remember that the is not locally $u(1)$-invariant. How do I prove this explicitly in field theory? | Why can't photons have a mass? Could you explain this to me in a short and mathematical way? | The Higgs boson and gluons have no electric charge and photons couple to charge, so there is no tree level interaction between them and photons. But what prevents higher order diagrams from contributing a non-zero mass term to the photon, for instance where a photon couples to some fermion (say an electron, or a top quark) which can interact with the Higgs field. Or consider that same diagram but with quarks and a gluon interacting between them? Or any higher diagram with even more loops? I have heard charge conservation depends on gauge invariance, which in turn depends on photons being massless. So it appears the photon has no mass, and these diagrams must all cancel somehow. So I'm hoping there is a very nice symmetry explanation for why they all disappear, but if I say "because of gauge invariance" that would be circular logic, so there must be another symmetry at stake here? What prevents photons from obtaining a mass from high-order self-energy loop diagrams? | eng_Latn | 26,944 |
Spontaneous Symmetry Breaking vs Addition of 'Mass terms' by hand | What goes wrong if we add a mass term for gauge bosons without the Higgs mechanism? | Intersection of all $p$-Sylow subgroups is normal | eng_Latn | 26,945 |
Higgs Coupling - Fifth Force | Why isn't Higgs coupling considered a fifth fundamental force? | Why isn't Higgs coupling considered a fifth fundamental force? | eng_Latn | 26,946 |
What happens if I add a single quark to a system of hadrons? | About free quarks and confinement | Moderator actions on items in the review queues don't count towards the review totals | eng_Latn | 26,947 |
Dubai pardons Norwegian woman who was jailed after reporting being raped .
5.9-magnitude earthquake leaves dozens dead in northwest China .
Hezbollah's military wing designated a terrorist group by EU . | (CNN) -- While half of civilization busied itself trying to find out the name, weight, gender, hair color, taste in music and political disposition of the new heir to the British throne, it turns out there was a whole world of other news happening out there. Here are five other stories you may have missed today: . 1. Dubai pardons woman jailed after reporting rape . A 24-year-old Norwegian woman says she was raped by a colleague in a Dubai hotel following a work party -- but after she went to police, she was convicted and sentenced to 16 months in jail on charges of having unlawful sex, making a false statement and illegal consumption of alcohol. Now Dubai's ruler has pardoned Marte Deborah Dalelv according to Norway's foreign minister, who called Dalelv's conviction "contrary to fundamental human rights." Dalelv will be free to travel where she wants and can remain in Dubai if she chooses. 2. Dozens dead as earthquake hits northwest China . A shallow, powerful 5.9-magnitude earthquake tore through China's Gansu Province, killing at least 89 people and injuring hundreds more, according to state media. The original quake and powerful aftershocks caused roofs to collapse, cut telecommunications lines and damaged a major highway. Emergency services have converged on the area to try to rescue survivors. 3. Hezbollah's military wing is a terrorist group, says EU . The European Union has joined the U.S. and Israel in designating the military wing of Hezbollah as a terrorist organization, but stopped short of putting the entire group on its terror list. The Bulgarians cited evidence that the military wing of the Iranian-backed Lebanese Shiite group was involved in a terror attack last year that killed five Israeli tourists and a Bulgarian bus driver. In Cyprus earlier this year, a court found a Hezbollah member guilty of assisting in the planning of an attack on Israel. Lately, its fighters have sided with Syrian President Bashar al-Assad in that country's civil war. The designation, which a spokeswoman for Israeli Justice Minister Tzipi Livni called "correct and just," would freeze the assets of Hezbollah entities. 4. Man who bombed Beijing airport wanted to flag 'unjust treatment' The wheelchair-bound Ji Zhongxing, 34, set off a homemade explosive inside a Beijing airport on Saturday after he was stopped from handing out leaflets "to get attention to his complaints" outside the arrival hall, according to Xinhua news agency. Ji said on his personal blog in 2006 that he had been beaten by security guards outside a police station in 2005 after carrying a passenger on his motorcycle -- a charge the police denied. He was paralyzed after the incident and petitioned for official compensation. Ji was hospitalized after he detonated his explosives. No other people were injured and flights at the airport were not affected. 5. CNN Exclusive: Glee star Charice on why she'll miss Cory Monteith . In an exclusive opinion piece for CNN.com, "Glee" star Charice writes that her body went cold when she learned co-star Cory Monteith had been found dead from a drug overdose in his hotel room in Vancouver. Charice says Monteith, who had been frank about his struggles with substance abuse in the past, was a "real talent" -- and that she has no idea what will happen to the hit American musical now that the actor is gone. | CERN's Large Hadron Collider will be turned back on in March - at double power, scientists revealed today. The world's biggest particle collider, located near Geneva, has been undergoing a two-year refit. Work is now 'in full swing' to start circulating proton beams again in March, with the first collisions due by May, the European Organization for Nuclear Research said. Scroll down for video . A worker stands below the Compact Muon Solenoid (CMS), a general-purpose detector at CERN's Large Hadron Collider, during maintenance works. Deep below the border between Switzerland and France, the tunnel stretches out of sight, decked with silver installations fit for a starship . 'With this new energy level, the (collider) will open new horizons for physics and for future discoveries,' CERN Director General Rolf Heuer said in a statement. 'I'm looking forward to seeing what nature has in store for us.' CERN's collider is buried in a 27-km (17-mile) tunnel straddling the Franco-Swiss border at the foot of the Jura mountains. The entire machine is already almost cooled to 1.9 degrees above absolute zero in preparation for the next three-year run. The first run, carried out at lower power, led in 2012 to confirmation of the existence of the Higgs boson particle, which explains how fundamental matter took on the mass to form stars and planets. That discovery was a landmark in physics but there are still plenty of other mysteries to be unraveled, including the nature of 'dark matter' and 'dark energy'. Latest calculations suggest that dark matter accounts for 27 percent of the universe and dark energy, which drives galaxies apart, 68 percent, while the visible matter observed in galaxies, stars and planets makes up just 5 percent. Scientists look at a section of the LHC while it is switched off. A year ago, the world's largest particle collider made one of the greatest discoveries in the history of science, identifying what is believed to be the Higgs Boson -- the long-sought maker of mass . Other unsolved questions include the relative lack of antimatter in the universe, when equal amounts of matter and antimatter were created in the Big Bang 13.8 billion years ago, and the possible existence of other new kinds of particles. Many physicists favor a yet-to-be-proven theory known as super-symmetry, in which all basic particles have a heavier but invisible 'super' partner. Getting to grips with such issues requires deeper insights into the building blocks of the cosmos, which researchers hope to achieve by turning up the dial at CERN to higher energies. 'We have unfinished business with understanding the universe,' said Tara Shears, a physics professor at the University of Liverpool, who works on one of the four main experiments at the collider. A worker walks past the Compact Muon Solenoid - part of the LHC. The 27 kilometre circular lab went offline in February for an 18-month overhaul. When experiments resume in 2015, scientists at CERN will use its enhanced power to probe dark matter, dark energy and supersymmetry . As engineers focus on the technical mission, physicists are sifting through the mountains of data that the Large Hadron Collider (LHC) has churned out since 2010, for there could be more nuggets to find. 'The things that are easy to spot have already been exploited, and now we're taking another look,' said Tiziano Camporesi of CERN, noting wryly that dealing with the unknown was, well, unknowable. 'We always say that astronomers have an easier task, because they can actually see what they're looking for!' The LHC's particle collisions transform energy into mass, the goal being to find fundamental particles in the sub-atomic debris that help us to understand the universe. At peak capacity, the 'old' LHC managed a mind-boggling 550 million collisions per second. 'We give the guys as many collisions as we can,' said Mike Lamont, head of its operating team. 'That's our bread and butter. Most of that stuff is not very interesting, so there are real challenges sorting out and throwing most of that away, and picking out the interesting stuff,' he explained in the tunnel, which mixes installations fit for a starship with the low-tech practicality of bicycles for inspection tours. CERN's supercomputers are programmed to identify within microseconds the collisions worth more analysis - chunks of a few hundred per second - before thousands of physicists from across the globe comb the results to advance our knowledge of matter. The LHC's computer screens are dark, but behind the scenes, work is pushing ahead to give the vast machine a mighty upgrade, enabling the collider to advance the frontiers of knowledge even farther . 'We want to understand how that behaves, why it sticks itself together into tiny things that we call atoms and nuclei at really small scales, into things that we call people and chairs and buildings at bigger scales, and then planets and solar systems, galaxies at larger scales,' said CERN spokesman James Gillies. CERN's work can bemuse beginners, but the researchers find ways to make it simple. 'Everybody knows what an electron is, especially if they put their finger in an electric socket,' joked Pierluigi Campana, whose team has just provided the most exhaustive confirmation to date of the Standard Model, the chief theoretical framework of particle physics conceived in the 1970s. At peak capacity, the 'old' LHC managed a mind-boggling 550 million collisions per second. 'We give the guys as many collisions as we can,' said Mike Lamont, head of its operating team. Here, an engineer observes the Compact Muon Solenoid . They achieved the most accurate measurement yet of a change in a particle called a Bs, showing that out of every billion, only a handful decay into smaller particles called muon, and do so in pairs. For the experts, that finding was almost as thrilling as tracking the Higgs boson -- nicknamed the God Particle. It was theorised in 1964 by British physicist Peter Higgs and others in an attempt to explain a nagging anomaly - why some particles have mass while others, such as light, have none. As engineers (pictured) focus on the technical mission, physicists are sifting through the mountains of data that the LHC has churned out since 2010, for there could be more nuggets to find . It is believed to act like a fork dipped . in syrup and held up in dusty air. While some dust slips through . cleanly, most gets sticky - in other words, acquires mass. With mass . comes gravity, which pulls particles together. The Standard Model is a trusty conceptual vehicle but it still lacks an explanation for gravity, nor does it account for dark matter and dark energy, which comprise most of the cosmos and whose existence is inferred from their impact on ordinary matter. Some physicists champion supersymmetry, the notion that there are novel particles which mirror each known particle. A worker rides his bike in a tunnel of the LHC. When it is back in business, the supercomputers are programmed to identify the collisions worth more analysis - chunks of a few hundred per second - before thousands of physicists from across the globe comb the results to advance our knowledge of matter . 'We have a theory that describes all the stuff around us, all the ordinary, visible matter that makes up the Universe. Except, the problem is, it doesn't. It makes up around five percent of the Universe,' said Gillies. The LHC replaced the Large Electron-Positron Collider (LEP), which ran from 1989 to 2000. I . It came online in 2008, but ran into problems, forcing a year-long refit. The LHC's particle collisions transform energy into mass, the goal being to find fundamental particles in the sub-atomic debris that help us to understand the universe. Here a scientist gestures in front of a diagram of one of the many goings on at the LHC . It went on to reach a collision level of eight teraelectron volts (TeV) -- an energy measure -- compared to the LEP's 0.2 TeV. After the 50 million Swiss franc ($54-million, million-euro) upgrade, the target is 14 TeV, meaning bigger bangs and clearer snapshots. ''Every time we pass a significant amount of data collected, someone will find an excuse to open a bottle of champagne,' said physicist Joel Goldstein, glancing at a lab corner piled with empties.'We're going to run out of space eventually!' The particle was theorised in 1964 by British physicist Peter Higgs and others in an attempt to explain a nagging anomaly - why some particles have mass while others, such as light, have none. The search more knowledge about the Higgs Boson will resume when the LHC opens again after its upgrade . | eng_Latn | 26,948 |
Physicists discovered a new particle that appears to be the highly sought after Higgs boson .
Lawrence Krauss: Our understanding of physical reality has changed forever .
He says the Higgs is the key to unlocking the question: Why does matter have mass?
Krauss: Higgslike particle gets us closer to solving the mystery of the universe and our origin . | (CNN) -- Our understanding of physical reality — of everything and nothing — has changed forever. We don't yet know where we are heading, but nothing will ever be the same. As a scientist, I don't know what more I could ask for. On July 4, two independent teams of more than 3,000 physicists apiece from more than 40 countries working at the largest particle accelerator on Earth at the European Center for Nuclear Research, or CERN, gathered to announce to the world the discovery of a new elementary particle. This was not just any elementary particle. It was a particle that appears to have all the characteristics of the Higgs boson, which was first predicted by physicists in 1964 and became the most sought-after particle ever since. The Higgs particle is an essential part of the Standard Model of particle physics, one of the most beautiful theories ever created by the human mind. The model provides an eloquent description of almost all of nature as we have observed in experiments in a few equations that can fit on a T-shirt. The only problem was that no experiment had ever provided evidence that the Higgs particle actually exists. News: Higgs boson is like... a Justin Bieber fan? Without the Higgs, the heart of the Standard Model is missing. The Higgs is associated with an invisible field predicted to permeate throughout all of space interacting with particles to give them mass. The Higgs is the key to unlocking the question: Why does matter have mass? Equally importantly, the Higgs allows two of the four forces in nature -- the electromagnetic force and the weak force, which is responsible for most nuclear reactions -- to be unified and described by mathematics of the same type that describe the other two known forces, the so-called strong force and gravity. Quantum mechanics tells us that if such a Higgs field exists, then one can produce real particles out of the field if one throws enough energy into a small enough volume. The discovery of this new particle is notable for what it tells us, but also for what it doesn't. There were some intriguing anomalies in the observation of this Higgslike particle. For example, the rate at which the new particle is produced seems to be slightly higher than the one predicted in the Standard Model. However, this could merely be a statistical fluke that results from the fact that to date only a few score of Higgs candidate events have been observed amongst billions of particle collisions. There are still important unanswered questions about the Standard Model and we have to verify that this remarkable theoretical house of cards can stand on its own. Deviations from the Standard Model prediction, if they are confirmed by more data, can shed light on these unknowns. What is the Higgs boson and why is it important? First and foremost is the question of how the invisible background field tied to the existence of the Higgs came to be and why it has the properties it does. This field is simply posited to exist, and apparently it does. The Higgslike particle takes us a step closer to solving the mystery of the universe, which is inextricably connected to the mystery of our own origin. Likewise, other new physics is now more likely to be uncovered at CERN's Large Hadron Collider, which will add to our knowledge base. We might, for example, find the particles that make up more than 90% of the matter in our galaxy and all galaxies, which look dark to our eyes. And we might be provided with clues that reveal the trail to unraveling the ultimate holy grail of fundamental particle physics -- a quantum theory of gravity. Imagine that the visible universe and everything in it was once contained in a volume many times smaller than the size of a single atom. With a quantum theory of gravity, we may be able to trace the Big Bang expansion back to its very beginning, and understand precisely how our universe arose, presumably from nothing. Read more science news on Light Years . Whatever new door to reality the discovery of Higgs opens for us, the best days may be ahead. That possibility is what energizes us, and makes the continued effort to probe new corners of nature such an exciting part of the human adventure. The opinions expressed in this commentary are solely those of Lawrence M. Krauss. | (CNN)What do you get when you combine Japanese culture, rock and musical theater? Chaos. Or more precisely KAO=S -- a band of spellbinding musicians presenting vivid visual performances unlike anything you may have ever seen. Following the devastating tsunami in 2011, the trio came together with the mission of creating something beautiful out of the turmoil. The result is an unusual musical style that blends the vocals and raw acoustic guitar of frontman Shuji Yamagiri with traditional Japanese instruments like the three-string Tsugaru-shamisen played by a musician known as Jack. The two instrumentalists are accompanied by powerful sword dancing from "Lady Samurai," aka Kaori Kawabuchi. "Music gives me imagination or inspiration by just listening to it. It's like I tell a story by using my body," Kawabuchi says of dancing with a samurai sword known as a katana. "I get an image from the sound by the (band) members under the conditions on that day, energy given by the audience, and the atmosphere." Kawabuchi's energetic sword dancing is a fluid, swift selection of movements that translate the musicians' deeply personal sound into a visual spectacle for the band's growing international audience. Since their conception, the band has played several high-profile gigs outside of Japan, including at the venerated annual SXSW music and media festival in Austin, Texas. They've also completed a tour of the United States as well as performed for fans at festivals in Germany and England. Band leader Yamagiri adds: "A strength and characteristic of our band is, we have [Kawabuchi] between us, and through her movement, she expresses the feeling of sadness and delight that we try to express in our play, using her body. "I think it makes it easier for an overseas audience to understand. She can deliver feminine delicacy and tenderness, and also intensity, which is even stronger than men." Watch the video to learn more about how KAO=S is turning their live gigs into a visually stimulating sensory experience. | eng_Latn | 26,949 |
What are the weaknesses of durkheim? Request | What are the weaknesses of durkheim? | Is de Broglie's subquantic medium a strongly interacting dark matter? Is there evidence of the dark matter when a double slit experiment is performed? | eng_Latn | 26,950 |
The 27 km circular lab went offline .
in February but will reopen in March with more firepower to help scientists solve the mysteries of the universe .
A year ago, the Large Hadron Collider made one of the greatest discoveries in the history of .
science, identifying what is believed to be the Higgs boson .
As engineers focus on the technical .
mission, physicists are sifting through data that the mighty atom smasher has churned out since 2010 . | CERN's Large Hadron Collider will be turned back on in March - at double power, scientists revealed today. The world's biggest particle collider, located near Geneva, has been undergoing a two-year refit. Work is now 'in full swing' to start circulating proton beams again in March, with the first collisions due by May, the European Organization for Nuclear Research said. Scroll down for video . A worker stands below the Compact Muon Solenoid (CMS), a general-purpose detector at CERN's Large Hadron Collider, during maintenance works. Deep below the border between Switzerland and France, the tunnel stretches out of sight, decked with silver installations fit for a starship . 'With this new energy level, the (collider) will open new horizons for physics and for future discoveries,' CERN Director General Rolf Heuer said in a statement. 'I'm looking forward to seeing what nature has in store for us.' CERN's collider is buried in a 27-km (17-mile) tunnel straddling the Franco-Swiss border at the foot of the Jura mountains. The entire machine is already almost cooled to 1.9 degrees above absolute zero in preparation for the next three-year run. The first run, carried out at lower power, led in 2012 to confirmation of the existence of the Higgs boson particle, which explains how fundamental matter took on the mass to form stars and planets. That discovery was a landmark in physics but there are still plenty of other mysteries to be unraveled, including the nature of 'dark matter' and 'dark energy'. Latest calculations suggest that dark matter accounts for 27 percent of the universe and dark energy, which drives galaxies apart, 68 percent, while the visible matter observed in galaxies, stars and planets makes up just 5 percent. Scientists look at a section of the LHC while it is switched off. A year ago, the world's largest particle collider made one of the greatest discoveries in the history of science, identifying what is believed to be the Higgs Boson -- the long-sought maker of mass . Other unsolved questions include the relative lack of antimatter in the universe, when equal amounts of matter and antimatter were created in the Big Bang 13.8 billion years ago, and the possible existence of other new kinds of particles. Many physicists favor a yet-to-be-proven theory known as super-symmetry, in which all basic particles have a heavier but invisible 'super' partner. Getting to grips with such issues requires deeper insights into the building blocks of the cosmos, which researchers hope to achieve by turning up the dial at CERN to higher energies. 'We have unfinished business with understanding the universe,' said Tara Shears, a physics professor at the University of Liverpool, who works on one of the four main experiments at the collider. A worker walks past the Compact Muon Solenoid - part of the LHC. The 27 kilometre circular lab went offline in February for an 18-month overhaul. When experiments resume in 2015, scientists at CERN will use its enhanced power to probe dark matter, dark energy and supersymmetry . As engineers focus on the technical mission, physicists are sifting through the mountains of data that the Large Hadron Collider (LHC) has churned out since 2010, for there could be more nuggets to find. 'The things that are easy to spot have already been exploited, and now we're taking another look,' said Tiziano Camporesi of CERN, noting wryly that dealing with the unknown was, well, unknowable. 'We always say that astronomers have an easier task, because they can actually see what they're looking for!' The LHC's particle collisions transform energy into mass, the goal being to find fundamental particles in the sub-atomic debris that help us to understand the universe. At peak capacity, the 'old' LHC managed a mind-boggling 550 million collisions per second. 'We give the guys as many collisions as we can,' said Mike Lamont, head of its operating team. 'That's our bread and butter. Most of that stuff is not very interesting, so there are real challenges sorting out and throwing most of that away, and picking out the interesting stuff,' he explained in the tunnel, which mixes installations fit for a starship with the low-tech practicality of bicycles for inspection tours. CERN's supercomputers are programmed to identify within microseconds the collisions worth more analysis - chunks of a few hundred per second - before thousands of physicists from across the globe comb the results to advance our knowledge of matter. The LHC's computer screens are dark, but behind the scenes, work is pushing ahead to give the vast machine a mighty upgrade, enabling the collider to advance the frontiers of knowledge even farther . 'We want to understand how that behaves, why it sticks itself together into tiny things that we call atoms and nuclei at really small scales, into things that we call people and chairs and buildings at bigger scales, and then planets and solar systems, galaxies at larger scales,' said CERN spokesman James Gillies. CERN's work can bemuse beginners, but the researchers find ways to make it simple. 'Everybody knows what an electron is, especially if they put their finger in an electric socket,' joked Pierluigi Campana, whose team has just provided the most exhaustive confirmation to date of the Standard Model, the chief theoretical framework of particle physics conceived in the 1970s. At peak capacity, the 'old' LHC managed a mind-boggling 550 million collisions per second. 'We give the guys as many collisions as we can,' said Mike Lamont, head of its operating team. Here, an engineer observes the Compact Muon Solenoid . They achieved the most accurate measurement yet of a change in a particle called a Bs, showing that out of every billion, only a handful decay into smaller particles called muon, and do so in pairs. For the experts, that finding was almost as thrilling as tracking the Higgs boson -- nicknamed the God Particle. It was theorised in 1964 by British physicist Peter Higgs and others in an attempt to explain a nagging anomaly - why some particles have mass while others, such as light, have none. As engineers (pictured) focus on the technical mission, physicists are sifting through the mountains of data that the LHC has churned out since 2010, for there could be more nuggets to find . It is believed to act like a fork dipped . in syrup and held up in dusty air. While some dust slips through . cleanly, most gets sticky - in other words, acquires mass. With mass . comes gravity, which pulls particles together. The Standard Model is a trusty conceptual vehicle but it still lacks an explanation for gravity, nor does it account for dark matter and dark energy, which comprise most of the cosmos and whose existence is inferred from their impact on ordinary matter. Some physicists champion supersymmetry, the notion that there are novel particles which mirror each known particle. A worker rides his bike in a tunnel of the LHC. When it is back in business, the supercomputers are programmed to identify the collisions worth more analysis - chunks of a few hundred per second - before thousands of physicists from across the globe comb the results to advance our knowledge of matter . 'We have a theory that describes all the stuff around us, all the ordinary, visible matter that makes up the Universe. Except, the problem is, it doesn't. It makes up around five percent of the Universe,' said Gillies. The LHC replaced the Large Electron-Positron Collider (LEP), which ran from 1989 to 2000. I . It came online in 2008, but ran into problems, forcing a year-long refit. The LHC's particle collisions transform energy into mass, the goal being to find fundamental particles in the sub-atomic debris that help us to understand the universe. Here a scientist gestures in front of a diagram of one of the many goings on at the LHC . It went on to reach a collision level of eight teraelectron volts (TeV) -- an energy measure -- compared to the LEP's 0.2 TeV. After the 50 million Swiss franc ($54-million, million-euro) upgrade, the target is 14 TeV, meaning bigger bangs and clearer snapshots. ''Every time we pass a significant amount of data collected, someone will find an excuse to open a bottle of champagne,' said physicist Joel Goldstein, glancing at a lab corner piled with empties.'We're going to run out of space eventually!' The particle was theorised in 1964 by British physicist Peter Higgs and others in an attempt to explain a nagging anomaly - why some particles have mass while others, such as light, have none. The search more knowledge about the Higgs Boson will resume when the LHC opens again after its upgrade . | (CNN) -- The Louvre has stood at the heart of Paris for 800 years - in turns, medieval fortress, royal chateau and renaissance palace. Most of the magnificent limestone edifice we see now is 17th, 18th and 19th century. For the last 220 years, it's been a people's museum. And with close to 10 million visitors a year, it's the most visited art museum in the world. Now we want to know what's your favorite work of art inside the Louvre. Is it one of the many magnificent paintings? Maybe it's the small portrait of the mysterious Mona Lisa. Or perhaps it's a collection of Egyptian figurines. Whatever it is, famous or obscure, small or big, we want to know, as long as it's an artwork in the public domain. Check out our instavid and tell us in the comment section below or via the hashtag #LouvreFavorite on Twitter, Facebook, Instagram, Google+ or Vine and you might be part of a special CNN.com feature. | eng_Latn | 26,951 |
Many of Yardley's colleagues were killed in the collapse of Canterbury Television news station .
Building collapsed when 6.3-magnitude earthquake struck Christchurch February 22 .
CTV is the longest-running television channel in New Zealand .
Yardley: CTV can and must rise again to serve the Canterbury region . | Christchurch, New Zealand (CNN) -- I was just leaving Newstalk ZB's building for the day when all hell broke loose. Fast-footing it in the middle of Worcester Street, I watched in raw terror as the Christchurch Club collapsed in front of me. A blood-soaked woman emerged out of the storm of dust and debris and after I assisted her to Latimer Square, it soon dawned on me that much of the city center was raining down on its citizens. Gazing to the south of Latimer Square, a billowing column of dust blocked any view of the CTV building. It wasn't until later in the day that I was confronted with the brutal reality that the dust wasn't blocking the view, but it was the dust of the building's remains. After frantically ensuring my family members were all safe, and taking stock of my own smashed-up house, my thoughts and prayers have been transfixed on my CTV family. For the past 10 years, the regional television channel has been a trusty employer for me, broadcasting my weekly current affairs program. At the time of writing, it would be inappropriate for me to name all of the staff that have been killed in this mass tragedy. My heart has been torn by the unwieldy weight of grief, as I reflect on 17 much-loved workmates who I will never share a TV studio with again. Seventeen passionate, resolute workmates who believed in regional television and made it work. CTV was not just "a shopping channel," as some people have scoffed. It served as a mirror on our region and that mirror has been so grotesquely shattered. And CTV has been the career launch-pad for dozens and dozens of TV journalists, who now appear on our nightly network news programs. CTV was the longest-running television channel in New Zealand, and although it will never be the same, it will rise again to serve our region. It must. One day at a time. Like many Cantabs, my mind is haunted with the apocalyptic scenes of our devastated city. I am sick to the pit of my stomach at the wrenching loss of life and casualty toll. Why did so many modern buildings implode? In hindsight, were we too impatient and "she'll be right" in agitating for the city center to return to "business as usual" so soon? How long should it be closed for now? What will it take before people trust our city center, and feel safe in the buildings that remain? How many people will trust the land they have lived and worked on? I know many Cantabs who simply cannot take it anymore and have abandoned the city they love, indefinitely. There are no fast solutions. For tens of thousands of folk, even securing basic services like power, water and sewage is going to be a marathon wait. Just as the Ellerslie Flower Show has been understandably cancelled, Christchurch's share of the Rugby World Cup does not look viable. Where will people stay? How fast can AMI Stadium be repaired? Should resources be diverted from key infrastructure work for the sake of this rugby tournament? There are so many questions and clouds of doubt. As much as we are exhorted to uphold our plucky, resilient spirit, I have huge fears about how much repair and rebuilding work can be done in time for winter. Can our viciously wounded city continue to support and sustain 400,000 people while major infrastructure and rebuilding work is undertaken? How can we seriously house everyone? I suspect a substantial portion of our population will need to relocate out of Christchurch, in the medium term, while the large-scale reconstruction work is carried out. Christchurch will rise again, Christchurch will shine again. But the slow road to recovery is going to be herculean. | CERN's Large Hadron Collider will be turned back on in March - at double power, scientists revealed today. The world's biggest particle collider, located near Geneva, has been undergoing a two-year refit. Work is now 'in full swing' to start circulating proton beams again in March, with the first collisions due by May, the European Organization for Nuclear Research said. Scroll down for video . A worker stands below the Compact Muon Solenoid (CMS), a general-purpose detector at CERN's Large Hadron Collider, during maintenance works. Deep below the border between Switzerland and France, the tunnel stretches out of sight, decked with silver installations fit for a starship . 'With this new energy level, the (collider) will open new horizons for physics and for future discoveries,' CERN Director General Rolf Heuer said in a statement. 'I'm looking forward to seeing what nature has in store for us.' CERN's collider is buried in a 27-km (17-mile) tunnel straddling the Franco-Swiss border at the foot of the Jura mountains. The entire machine is already almost cooled to 1.9 degrees above absolute zero in preparation for the next three-year run. The first run, carried out at lower power, led in 2012 to confirmation of the existence of the Higgs boson particle, which explains how fundamental matter took on the mass to form stars and planets. That discovery was a landmark in physics but there are still plenty of other mysteries to be unraveled, including the nature of 'dark matter' and 'dark energy'. Latest calculations suggest that dark matter accounts for 27 percent of the universe and dark energy, which drives galaxies apart, 68 percent, while the visible matter observed in galaxies, stars and planets makes up just 5 percent. Scientists look at a section of the LHC while it is switched off. A year ago, the world's largest particle collider made one of the greatest discoveries in the history of science, identifying what is believed to be the Higgs Boson -- the long-sought maker of mass . Other unsolved questions include the relative lack of antimatter in the universe, when equal amounts of matter and antimatter were created in the Big Bang 13.8 billion years ago, and the possible existence of other new kinds of particles. Many physicists favor a yet-to-be-proven theory known as super-symmetry, in which all basic particles have a heavier but invisible 'super' partner. Getting to grips with such issues requires deeper insights into the building blocks of the cosmos, which researchers hope to achieve by turning up the dial at CERN to higher energies. 'We have unfinished business with understanding the universe,' said Tara Shears, a physics professor at the University of Liverpool, who works on one of the four main experiments at the collider. A worker walks past the Compact Muon Solenoid - part of the LHC. The 27 kilometre circular lab went offline in February for an 18-month overhaul. When experiments resume in 2015, scientists at CERN will use its enhanced power to probe dark matter, dark energy and supersymmetry . As engineers focus on the technical mission, physicists are sifting through the mountains of data that the Large Hadron Collider (LHC) has churned out since 2010, for there could be more nuggets to find. 'The things that are easy to spot have already been exploited, and now we're taking another look,' said Tiziano Camporesi of CERN, noting wryly that dealing with the unknown was, well, unknowable. 'We always say that astronomers have an easier task, because they can actually see what they're looking for!' The LHC's particle collisions transform energy into mass, the goal being to find fundamental particles in the sub-atomic debris that help us to understand the universe. At peak capacity, the 'old' LHC managed a mind-boggling 550 million collisions per second. 'We give the guys as many collisions as we can,' said Mike Lamont, head of its operating team. 'That's our bread and butter. Most of that stuff is not very interesting, so there are real challenges sorting out and throwing most of that away, and picking out the interesting stuff,' he explained in the tunnel, which mixes installations fit for a starship with the low-tech practicality of bicycles for inspection tours. CERN's supercomputers are programmed to identify within microseconds the collisions worth more analysis - chunks of a few hundred per second - before thousands of physicists from across the globe comb the results to advance our knowledge of matter. The LHC's computer screens are dark, but behind the scenes, work is pushing ahead to give the vast machine a mighty upgrade, enabling the collider to advance the frontiers of knowledge even farther . 'We want to understand how that behaves, why it sticks itself together into tiny things that we call atoms and nuclei at really small scales, into things that we call people and chairs and buildings at bigger scales, and then planets and solar systems, galaxies at larger scales,' said CERN spokesman James Gillies. CERN's work can bemuse beginners, but the researchers find ways to make it simple. 'Everybody knows what an electron is, especially if they put their finger in an electric socket,' joked Pierluigi Campana, whose team has just provided the most exhaustive confirmation to date of the Standard Model, the chief theoretical framework of particle physics conceived in the 1970s. At peak capacity, the 'old' LHC managed a mind-boggling 550 million collisions per second. 'We give the guys as many collisions as we can,' said Mike Lamont, head of its operating team. Here, an engineer observes the Compact Muon Solenoid . They achieved the most accurate measurement yet of a change in a particle called a Bs, showing that out of every billion, only a handful decay into smaller particles called muon, and do so in pairs. For the experts, that finding was almost as thrilling as tracking the Higgs boson -- nicknamed the God Particle. It was theorised in 1964 by British physicist Peter Higgs and others in an attempt to explain a nagging anomaly - why some particles have mass while others, such as light, have none. As engineers (pictured) focus on the technical mission, physicists are sifting through the mountains of data that the LHC has churned out since 2010, for there could be more nuggets to find . It is believed to act like a fork dipped . in syrup and held up in dusty air. While some dust slips through . cleanly, most gets sticky - in other words, acquires mass. With mass . comes gravity, which pulls particles together. The Standard Model is a trusty conceptual vehicle but it still lacks an explanation for gravity, nor does it account for dark matter and dark energy, which comprise most of the cosmos and whose existence is inferred from their impact on ordinary matter. Some physicists champion supersymmetry, the notion that there are novel particles which mirror each known particle. A worker rides his bike in a tunnel of the LHC. When it is back in business, the supercomputers are programmed to identify the collisions worth more analysis - chunks of a few hundred per second - before thousands of physicists from across the globe comb the results to advance our knowledge of matter . 'We have a theory that describes all the stuff around us, all the ordinary, visible matter that makes up the Universe. Except, the problem is, it doesn't. It makes up around five percent of the Universe,' said Gillies. The LHC replaced the Large Electron-Positron Collider (LEP), which ran from 1989 to 2000. I . It came online in 2008, but ran into problems, forcing a year-long refit. The LHC's particle collisions transform energy into mass, the goal being to find fundamental particles in the sub-atomic debris that help us to understand the universe. Here a scientist gestures in front of a diagram of one of the many goings on at the LHC . It went on to reach a collision level of eight teraelectron volts (TeV) -- an energy measure -- compared to the LEP's 0.2 TeV. After the 50 million Swiss franc ($54-million, million-euro) upgrade, the target is 14 TeV, meaning bigger bangs and clearer snapshots. ''Every time we pass a significant amount of data collected, someone will find an excuse to open a bottle of champagne,' said physicist Joel Goldstein, glancing at a lab corner piled with empties.'We're going to run out of space eventually!' The particle was theorised in 1964 by British physicist Peter Higgs and others in an attempt to explain a nagging anomaly - why some particles have mass while others, such as light, have none. The search more knowledge about the Higgs Boson will resume when the LHC opens again after its upgrade . | eng_Latn | 26,952 |
Is de Broglie's subquantic medium a strongly interacting dark matter? Is there evidence of the dark matter when a double slit experiment is performed? | Is there evidence of the strongly interacting dark matter that fills 'empty' space every time a double slit experiment is performed? Is it what waves? | Is there any tangible evidence for life after death? | eng_Latn | 26,953 |
The International Linear Collider aims to "discover an overarching theory of everything"
The vast new facility will increase understanding of the Higgs Boson, commonly known as the "God particle"
Research into the particle led to the awarding of this year's Nobel Prize in Physics . | (CNN) -- "Two professors, both alike in dignity, in fair Geneva where we lay our scene." When it is finally written, the story of one of the greatest scientific discoveries of our age may begin something like this. Last month, two eminent professors -- Peter Higgs and Francois Englert -- were jointly awarded one of science's greatest honours: the Nobel Prize in Physics. The award came on the back of the dramatic announcement last year that the Large Hadron Collider (LHC), based in Geneva, had made an astonishing discovery: a new particle, a Higgs Boson, had been comprehensively proven to exist. Physicists around the world rejoiced -- some wept openly. Years of speculation, theory and research had suddenly been validated. In typical Scandinavian understatement, Staffan Normark, permanent secretary of the Royal Swedish Academy of Sciences said "This year's prize is about something small that makes all the difference." The discovery came as a major puzzle piece in the way physicists understand the universe. The "Standard Model" of physics, which some regard as a "theory of almost everything" suffered from a significant "missing link" before the discovery of the Higgs Boson. Now there seemed to be a reason why particles have mass; now we had a key to understanding our 4% of the universe and perhaps access to understanding the other 96% of the universe as well. But just as one set of answers were being revealed, more questions immediately presented themselves. CNN Labs spoke to some of the world's top physicists about what the discovery of the Higgs Boson means, and what questions now need to be addressed. Joel Butler, a scientist at the prestigious Fermilab laboratory in Illinois said: "The big question is why the Higgs (particle), with a mass more than 100 times that of the proton, is so light. That question is not answered by our picture of the universe" Jon Butterworth, Head of Physics and Astronomy at University College London, says that in his view: "There are issues like what is dark matter? (And) why is the universe mostly matter not antimatter?" Hitoshi Murayama, a professor of physics at UC Berkeley, says: "The main question is this: we have never seen an elementary particle without spin. Electron, quarks, photon, etc all have spins ... The Higgs boson may actually have spin but it is spinning in extra dimensions of space we cannot see. We really need to know the true nature and context of this newly discovered particle." To answer these questions the Large Hadron Collider will soon be joined by another massive experimental facility -- the International Linear Collider (ILC). Like the LHC, the ILC will be a vast machine that stretches for miles beneath the earth. A site for the ILC has yet to be determined. The history of science is replete with machines that have helped scientists make significant breakthroughs, providing the kind of quantifiable, testable, reproducible data science requires to progress. From Marie Curie's ionization chamber used in the discovery of spontaneous radioactivity, to Cathode ray tubes which led to the discovery of the electron, to Geiger counters and more recently the Large Hadron Collider, discoveries have come from equipment both big and small; simple and complex. The ILC sits as the latest in a long line of machines designed to advance physics, but what exactly will it do that the LHC cannot? Tim Meyer, Head of Strategic Planning and Communications at TRIUMF, Canada's national laboratory for particle and nuclear physics, says that it will be able to produce many more Higgs particles than the vast collider in Geneva, and will offer new levels of accuracy. "The ILC will be able to study the Higgs precisely," he said. "It will be a Higgs factory and will be able to make measurements of the Higgs' properties with 3% relative precision as opposed to the LHC's 25% relative precision, people believe ... The ILC could 'crack open the Higgs' and reveal the mysteries of nature's first spin-zero particle." Brian Foster, the European Regional Director for the International Linear Collider, says that it is not impossible that the vast machine could help us discover an overarching theory of everything. "If we are lucky, the ILC can detect a whole new family of particles that might help us to realize Einstein's dream of uniting all the theories of physics into one overarching and conceptually simple theory," Foster says. A decision to begin construction on the International Linear Collider is currently expected by 2015. Monique Rivalland contributed to this article . | TOWIE star and footballer Jake Hall scored a vital goal for non-league side Boston United on Monday - impressing his on-screen girlfriend Chloe Lewis in the stands. Hall scored with his first touch just moments after coming off the bench to keep the Pilgrims on course for a place in the Conference North play-offs. And it put a smile on the face of Lewis, his on-off girlfriend in the popular Essex-based ITV show, who was watching on at York Street. TOWIE star Jake Hall points to his co-star Chloe Lewis in the stands at York Street after scoring for Boston United in their Conference North match with Tamworth on Monday . TOWIE star James 'Arg' Argent was also in the crowd to see Hall score with his first touch . 'Arg' tries to get onto the pitch to celebrate after Hall scored Boston's second goal . With her was Hall's friend and TOWIE co-star James 'Arg' Argent, who leaned over the hoardings to celebrate when he netted during the second-half of Boston's 2-0 win over Tamworth. Hall hit the headlines this week after reports he is dating Hollywood actress Lindsay Lohan after they were spotted out in Soho together. Both parties denied any relationship, saying they were just friends. Semi-professional footballer Hall, who played 15 matches for Boston last season before rising to fame on the TV series, rejoined the Lincolnshire club last week. Reports this week suggested Hall has secretly been dating Hollywood actress Lindsay Lohan - pictured here attending Soho nightclub The Box together in February . The Only Way is Essex stars Jake Hall and Chloe Lewis pictured together on the show . He told the Boston Target after the game: 'It was mental, on my left peg as well, you can't write that, I'm still in shock. 'Chloe was at the game and I could see her jumping up and down when I scored the goal. That one was for her. 'The buzz around the crowd today was immense. It was electric and gave me a real buzz. 'I love this club. If I could be here full-time, I would be. The crowd are amazing and the boys make you feel so welcome. It's a special club.' Boston manager Dennis Greene added: 'He brought his girlfriend Chloe and Arg with him today. Arg was so excited when Jake scored he was trying to get over the barriers. It was funny and a really brilliant moment.' | eng_Latn | 26,954 |
The picture follows the convention of the time axis being on the vertical direction. I think this Feynman diagram represents Coulomb repulsion between two electrons with a virtual photon being absorbed and emitted by each electron. What are the arrows on the electron lines for? I'm not sure what information this tells us. | The momentum-space fermion propagator in the free Dirac theory is given by The arrow on the fermion propagator is said to represent the flow of charge. How can we derive this statement quantitatively from the Dirac Lagrangian? What is the quantitative form of the charge being referred to here? | Prove that there is no retraction (i.e. continuous function constant on the codomain) $r: M \rightarrow S^1 = \partial M$ where $M$ is the Möbius strip. I've tried to find a contradiction using $r_*$ homomorphism between the fundamental groups, but they are both $\mathbb{Z}$ and nothing seems to go wrong... | eng_Latn | 26,955 |
The energy scale of is around $160$ GeV. But the LHC has a centre of mass energy of $7$ TeV... so do they see processes involving the $W^1, W^2, W^3$ and $B$ fields, before spontaneous symmetry breaking and mixing into the well-know massive gauge bosons + photon? | Spontaneous electroweak symmetry breaking (i.e. $SU(2)\times U(1)\to U(1)_{em}$ ) is at scale about 100 Gev. So, for , gauge bosons $Z$ & $W$ have masses about 100 GeV. But before this spontaneous symmetry breaking ( i.e. Energy > 100 GeV) the symmetry $SU(2)\times U(1)$ is not broken, and therefore gauge bosons are massless. The same thing happens when we go around energy about $10^{16}$ GeV, where we have the Grand Unification between electroweak and strong interactions, in some bigger group ($SU(5)$, $SO(10)$ or others). So theoretically we should find gauge bosons $X$ and $Y$ with masses about $10^{16}$ GeV after GUT symmetry breaks into the Standard Model gauge group $SU(3)\times SU(2)\times U(1)$, and we should find massless X and Y bosons at bigger energies (where GUT isn't broken). So this is what happened in the early universe: when temperature decreased, spontaneous symmetry breaking happened and firstly $X$ & $Y$ gauge bosons obtained mass and finally $Z$ & $W$ bosons obtained mass. Now, I ask: have I understood this correctly? In other words, if we make experiments at energy above the electroweak scale (100 GeV) we are where $SU(2)\times U(1)$ isn't broken and then we should (experimentally) find $SU(2)$ and $U(1)$ massless gauge bosons, i.e. $W^1$, $W^2$, $W^3$ and $B$ with zero mass? But this is strange, because if I remember well in LHC we have just make experiments at energy about 1 TeV, but we haven't discovered any massless gauge bosons. | The relativistic energy-momentum equation is: $$E^2 = (pc)^2 + (mc^2)^2.$$ Also, we have $pc = Ev/c$, so we get: $$E = mc^2/(1-v^2/c^2)^{1/2}.$$ Now, accelerating a proton to near the speed of light, I get the following results for the energy of proton: 0.990000000000000 c => 0.0000000011 J = 0.01 TeV 0.999000000000000 c => 0.0000000034 J = 0.02 TeV 0.999900000000000 c => 0.0000000106 J = 0.07 TeV 0.999990000000000 c => 0.0000000336 J = 0.21 TeV 0.999999000000000 c => 0.0000001063 J = 0.66 TeV 0.999999900000000 c => 0.0000003361 J = 2.10 TeV 0.999999990000000 c => 0.0000010630 J = 6.64 TeV 0.999999999000000 c => 0.0000033614 J = 20.98 TeV 0.999999999900000 c => 0.0000106298 J = 66.35 TeV 0.999999999990000 c => 0.0000336143 J = 209.83 TeV 0.999999999999000 c => 0.0001062989 J = 663.54 TeV 0.999999999999900 c => 0.0003360908 J = 2,097.94 TeV 0.999999999999990 c => 0.0010634026 J = 6,637.97 TeV 0.999999999999999 c => 0.0033627744 J = 20,991.10 TeV If the LHC is accelerating protons to $7 TeV$ it means they're traveling with a speed of $0.99999999c$. Is everything above correct? | eng_Latn | 26,956 |
Fusion of quarks release 8 times more energy than hydrogen fusion, so I was wondering if quark star exists and before quark degeneracy pressure kicks in wouldn't these tightly packed sea of quarks start fusing and eventually becoming a miniature neutron star? I think in normal scenario due to the short range of strong force and quark/neutron cannot be found alone in nature compare to the condition of quark star where quarks should easily fused with each other and outshines almost everything in the night sky. | A quark star is a hypothetical type of compact exotic star composed of quark matter. These are ultra-dense phases of degenerate matter theorized to form inside particularly massive[citation needed] neutron stars. -Wikipedia If you add enough mass to a neutron star it forms a black hole but how much mass is needed to form a quark star? When do neutrons and protons start to break down into a mush of quarks and gluons? | The entire site is blank right now. The header and footer are shown, but no questions. | eng_Latn | 26,957 |
Why do no particles have a 1/3 spin? Why are all particles' spin either a half-integer or integer? How would a particle with such a spin behave, as a fermion, boson, or neither? | It seems to me that we could change all the current spin values of particles by multiplying them by two. Then we could describe Bosons as even spin particles and Fermions as odd spin particles. Is there some consequence or reason why we can't simply change 1/2 as the smallest unit of spin into 1? It just seems prettier this way. In fact, there's almost an interesting relation to even and odd functions in that if you switch any two bosons around the wave function stays the same while if you switch any two fermions around the wave function becomes negative. | It seems to me that we could change all the current spin values of particles by multiplying them by two. Then we could describe Bosons as even spin particles and Fermions as odd spin particles. Is there some consequence or reason why we can't simply change 1/2 as the smallest unit of spin into 1? It just seems prettier this way. In fact, there's almost an interesting relation to even and odd functions in that if you switch any two bosons around the wave function stays the same while if you switch any two fermions around the wave function becomes negative. | eng_Latn | 26,958 |
The higgs boson is an elementary particle so how it can decays into another elementary particle; the photon? And why the photon doesn't interact with the Higgs field? | Why don’t photons interact with the Higgs field and hence remain massless? | Why don’t photons interact with the Higgs field and hence remain massless? | eng_Latn | 26,959 |
Why do we not observe any free quarks or gluon, but only particles that are built out of them, such as mesons and baryons? How does this phenomenon emerge from QCD? | I simply know that a single free quark does not exist. What is the reason that we can not get a free quark? If we can't get a free quark then what is single-top-quark? | was created on Server Fault, answered on Server Fault, I upvoted some of those answers on Server Fault, and then moved by consensus to Super User. Now that the question is on Super User, I can upvote the same answers I previously upvoted on Server Fault. | eng_Latn | 26,960 |
Can Quantum Teleportation be accomplished faster than the speed of light? Let us say Alice wants to communicate state |T> (also a qubit) to Bob. Given, they have an EPR Pair shared amongst them. Alice interacts her qubit with |T> and then sends the measured state (classical information) of qubits to Bob. Depending upon the measured state of qubits(00,01,10,11) Bob uses the quantum gates to get back |T>. But instead of doing that Bob could have decided upon using a particular quantum gate. So, he could have got the right information with a probability of 0.25 but at least he could have achieved faster than light teleportation with a probability of 0.25. | Can't quantum teleportation be superluminal some percentage of times? I apologize if this is a really silly question. In the (textbook) quantum teleportation algorithm, in the step right after Alice has measured her system but before she has sent her classical information to Bob, she is about to send one of the following values: 00,01,10,11. What if Bob doesn't want to wait and simply takes a guess? Wouldn't there then be superluminal communication 25% of the time? | What's the deepest reason why QCD bound states have integer charge? What's the deepest reason why QCD bound states have integer electric charge, i.e. equal to an integer times the electron charge? Given that the quarks have the fractional electric charges they do, this is a consequence of color confinement. The charges of the quarks are constrained in the context of the standard model by anomaly cancellation, and can be explained by grand unification. The GUT explanation for the charges doesn't care about the bound state spectrum of the QCD sector, so it just seems to be a coincidence that hadrons (which are composite) have integer charge, and that leptons (which are elementary) also have integer charge. Now maybe there's some anthropic argument for why such a coincidence is useful (in the case of proton and electron, it gives us atoms as we know them). Or maybe you can argue that GUTs naturally produce fractionally charged particles and strongly coupled sectors, and it's just not much of a coincidence. But I remain curious as to whether Seiberg duality, anyons, some UV/IR relationship... could really produce something like the lepton-hadron charge coincidence, for deeper reasons. I suppose one is looking for a theory in which properties of bound states in one sector have a direct and nontrivial relationship to properties of elementary states in another sector. Is there anything like this out there? (This question was prompted by muster-mark's many recent questions about fractional charge, and by a that the hadron-lepton charge coincidence is a "semi-coincidence", which assured me that I wasn't overlooking some obvious explanation.) | eng_Latn | 26,961 |
Observationally distinguishing a galaxy of antimatter from a galaxy of matter I was just wondering how, observationally, we would distinguish a distant galaxy of "normal" matter from one of antimatter. Maybe there is a simple answer but I don't see it. Once I started thinking about it, it bothered me. I will often come across an article that says (paraphrasing) cosmologists can't account for asymmetry in matter/antimatter in the observable universe. What technique do they use to distinguish the two remotely? Suns and "antisuns" would have the same spectra as would all the elements and their counterparts so far as I can tell. They have the same masses, so gravitationally they wouldn't be distinguishable. Am I missing something? | Experimental observation of matter/antimatter in the universe Ordinary matter and antimatter have the same physical properties when it comes to, for example, spectroscopy. Hydrogen and antihydrogen atoms produce the same spectroscopy when excited, and adsorb the same frequencies. The charge does not make a difference in the potential (regardless if it's generated by a proton or an antiproton) nor in how the positron behaves in this potential (being its mass equal to the mass of an electron) How can astronomy evaluate if a far galaxy is made of matter or antimatter, given that from the spectroscopy point of view, they behave in the same way? In other words, how do we know that an asymmetry exists between matter and antimatter in the universe? | Implications of parity violation for molecular biology In biology, the concept of parity emerges in the context of chiral molecules, where two molecules exist with the same structure but opposite parity. Interestingly, one enantiomer often strongly predominates over the other in natural biological systems (e.g. D-glucose is ubiquitous, L-glucose is rare in nature). In physics, it has been established that weak interactions violate parity, which (if I understand correctly) implies a physical difference between left- and right-handed systems. This suggests to me the following questions: Does parity violation in physics affect the physical or chemical properties of chiral molecules? And does this have any implications for our understanding of biological homochirality? | eng_Latn | 26,962 |
Non normalisability implies uncertainty principle? The wave function $\psi(x,t)$ for a free particle assuming that the position and momentum is well defined, can be solved from the schroedinger equation, $$\frac{-\hbar^2}{2m}\nabla^2\psi+V\psi=\hat{E}\psi$$ And that wave function is $$\psi(x,t)=Ae^{i(kx−\omega{t})}$$ and also we know that this wavefunction is not normalisable. Thus we conclude that this particle has no well defined momentum (and hence energy). But uncertainty principle says the same thing. That is, particle has no well defined momentum and position. Now, my question is that is these two concepts are same? That is, non-normalisability implies uncertainty principle? or is there a different conceptual explannation about the non normalisability of the wavefunction? I think a big mistake happened to me in understanding both these concepts. pls help | is there any uncertainty on the free particle with a definite momentum $\vec p$? The probability amplitude for a free particle with momentum $\ p$ and energy $E$ is the complex wave function: $$\psi_{(\vec x , t)}=e^{i(\vec k\cdot \vec x -\omega t)}$$ is there any uncertainty on the free particle with a definite momentum $\vec p$!? | What prevents photons from getting mass from higher order Feynman diagrams The Higgs boson and gluons have no electric charge and photons couple to charge, so there is no tree level interaction between them and photons. But what prevents higher order diagrams from contributing a non-zero mass term to the photon, for instance where a photon couples to some fermion (say an electron, or a top quark) which can interact with the Higgs field. Or consider that same diagram but with quarks and a gluon interacting between them? Or any higher diagram with even more loops? I have heard charge conservation depends on gauge invariance, which in turn depends on photons being massless. So it appears the photon has no mass, and these diagrams must all cancel somehow. So I'm hoping there is a very nice symmetry explanation for why they all disappear, but if I say "because of gauge invariance" that would be circular logic, so there must be another symmetry at stake here? What prevents photons from obtaining a mass from high-order self-energy loop diagrams? | eng_Latn | 26,963 |
What does the star mean in $\rightarrow ZZ^{(∗)}$? Z boson can neither be positive nor negative. "For masses above 130 GeV, Higgs-boson decays, H $\rightarrow ZZ^{(∗)}$, where each Z decays to a pair of oppositely charged leptons, would provide the experimentally cleanest channel to study the properties of the Higgs boson." Quoted from "The ATLAS Experiment at the CERN Large Hadron Collider" page 2 or 3 | I can always find that in some articles the production of higgs decay written as "$\rm H\to {ZZ}^*\to 4l$", "$\rm H\to ZZ\to 4l$", "$\rm H\to Z\gamma^*\to\ldots$” What dose it mean when some particles with a superscript *? Such as “$\rm Z^*, W^*, \gamma^*, \ldots$". What’s the difference between them and "$\rm Z, W, \gamma$"? | How do we show that equality holds in the triangle inequality $|a+b|=|a|+|b|$ iff both numbers are positive, both are negative or one is zero? I already showed that equality holds when one of the three conditions happens. | eng_Latn | 26,964 |
Extra Shottky Flyback Diodes on FET-based BLDC Motor Driver? TL;DR: I have a FET-based BLDC motor driver design, and I need to decide whether to add discrete Shottky diodes in parallel with each FET for reliable and long-lived operation in an automotive-like application. Yes? No? What do I need to consider? Longer version: I'm going through the details of a 3-phase BLDC (brushless DC) motor driver, and I'm debating whether to include discrete flyback diodes. The circuit looks like this one: A few other parameters: It's a 48V, 40A continuous (60A intermittent) driver. Reliability and toughness are a factor. This will see service as a traction motor driver in an automotive-like environment, for a small vehicle. The system will see operation in all . Since the FETs already have body diodes, there are technically flyback diodes in place already, which means that even if the active components fail, there will still be a path for currents to flow. The question is whether these are enough to handle all of the scenarios that come up during normal (read: abusive) operation in the field. I've considered adding a discrete Shottky diode in parallel with the FET body diode. In principle, since it has a lower forward voltage curve as well as a faster response time, any flyback currents should shunt through the Shottky instead of the FETs. If the current ever comes along, this is a good thing. But the question is, will there ever be a scenario where the body diodes aren't big enough to handle the heat? Does anyone have any experience as to whether adding discrete Shottkys in a FET-based motor driver bridge provides any benefit? If so, what do they protect against? | Body Diode of a MOSFET So for some MOSFETs, specially with Power MOSFETs, the body diode is a flyback diode that (as far as aI can tell) can be conveniently added to the MOSFET's bulk as there already PN junctions (correct me if I'm wrong). I've looked at the datasheet of a Power P-MOSFET and it has parameters like "Internal Source Inductance" and "Internal Drain Inductance". So, is the build up of reverse voltage on the source and drain sides, when said MOSFET is suddenly turned off, a behavior intrinsic to (at least some) MOSFETs? Or are these from the rest of the circuit, say inductive loads? | What role does "spontaneously symmetry breaking" played in the "Higgs Mechanism"? In talking about Higgs mechanism, the first part is always some introduction to the concept of spontaneously symmetry breaking (SSB), some people saying that Higgs mechanism is the results of SSB of local gauge symmetry, some people says that we can formulate Higgs mechanism in a gauge invariant way, some people also says that we need only a non-zero vaccum expectation value... I am confused about this different or maybe same point of views. In this post: , the most highly voted answer, I still can't feel how SSB worked in Higgs mechanism. It seem that the validity of last part, the appearance of a mass term for $A$, is guaranteed if we have a non-zero equilibrium value $\phi_0$ to expand around. I do not see that the requirement that the phase of the field $\phi$ need to be fixed at some particular value to generate mass term. Thus it seems to me it is not true that SSB is really indispensable for Higgs mechanism. To put it simply: The spontanously breaking of what is attributed to Higgs mechanism? local gauge symmetry global symmetry, since breaking of a "gauge symmetry" should not have any effect on physics. In higgs mechanism, the really broken symmetry is a global one. Mathematically, it is similar in looking as fixing a gauge, but one should not think it as a spontanously breakdown of local gauge symmetry. other. Is SSB really indispensable for Higgs mechanism? yes, Higgs mechanism is relied on the SSB of some symmetry (above question), the other approches of description eventually has spontanously broke some symmetry. No, the SSB is just one way to describe Higgs mechanism (or even not a complete way), what is really need is the non-zero vaccum expectation value, for example in the linked post the requirement for the mass term to occur is to have some non-zero expectation value of $\phi$ to expand around, we do not need the phase of the field to be fixed, thus the symmetry is not broken. Other. some reference materials: States that SSB of local gauge symmetry is impossible. in the abstract states that: gauge symmetries merely reflect a redundancy in the state description and therefore the spontaneous breaking can not be an essential ingredient. Indeed, as already shown by Higgs and Kibble, the mechanism can be explained in terms of gauge invariant variables, without invoking spontaneous symmetry breaking In the introduction it says: In particular, we emphasize that global U(1) phase rotation symmetry, and not gauge symmetry, is spontaneously violated, and show that the BCS wave function is, contrary to claims in the literature, fully gauge invariant | eng_Latn | 26,965 |
Which is a good and short book for foundations of quantum mechanics? I am looking for a book that has stuff on quantum states, entanglement, etc. I am aware of the book, Geometry of Quantum States. I have read Ballentine's book, Quantum Mechanics: A modern development | What is a good introductory book on quantum mechanics? I'm really interested in quantum theory and would like to learn all that I can about it. I've followed a few tutorials and read a few books but none satisfied me completely. I'm looking for introductions for beginners which do not depend heavily on linear algebra or calculus, or which provide a soft introduction for the requisite mathematics as they go along. What are good introductory guides to QM along these lines? | What's the deepest reason why QCD bound states have integer charge? What's the deepest reason why QCD bound states have integer electric charge, i.e. equal to an integer times the electron charge? Given that the quarks have the fractional electric charges they do, this is a consequence of color confinement. The charges of the quarks are constrained in the context of the standard model by anomaly cancellation, and can be explained by grand unification. The GUT explanation for the charges doesn't care about the bound state spectrum of the QCD sector, so it just seems to be a coincidence that hadrons (which are composite) have integer charge, and that leptons (which are elementary) also have integer charge. Now maybe there's some anthropic argument for why such a coincidence is useful (in the case of proton and electron, it gives us atoms as we know them). Or maybe you can argue that GUTs naturally produce fractionally charged particles and strongly coupled sectors, and it's just not much of a coincidence. But I remain curious as to whether Seiberg duality, anyons, some UV/IR relationship... could really produce something like the lepton-hadron charge coincidence, for deeper reasons. I suppose one is looking for a theory in which properties of bound states in one sector have a direct and nontrivial relationship to properties of elementary states in another sector. Is there anything like this out there? (This question was prompted by muster-mark's many recent questions about fractional charge, and by a that the hadron-lepton charge coincidence is a "semi-coincidence", which assured me that I wasn't overlooking some obvious explanation.) | eng_Latn | 26,966 |
Charged gravity: what magnitudes, if any, would be consistent with observations so far? (Disclaimer: the following might fit better on Worldbuilding - on the one hand, I'm not looking to write a story, but on the other, I don't know enough physics to know whether this is a trivial "no, save it for science fiction". Also could be considered a follow-up to ). Suppose for a moment that gravity is symmetric with electromagnetism, only with like "charges" attracting rather than repelling, and opposite charges repelling rather than attracting. At the macro scale, billions of years of opposite gravitational polarities mean a sort of segregation of positively and negatively "charged" particles, which seems a plausible surface explanation for the lack of antigravity in day-to-day life - but, as I said, I don't know the physics well enough (read: at all) to say how well that explanation holds up under closer scrutiny. At the micro scale, I don't know that we've had the capacity to observe the effects of gravity one way or the other on individual particles (to the extent that "individual particles" makes sense in modern physics), but while I'm on this hypothetical/crackpot bent I'd note that as long as the repulsive force from antigravity is exceeded by an attractive force from one of the other fundamental forces you could have, say, (obviously less stable) "hybrid" atoms, with a corresponding reduction in the observed gravitational force due to that atom. Averaged over lots* of atoms, and you'd have what appears to be gravity that's significantly weaker than other forces, due to some of it being cancelled out by the mixed-in antigravity particles (presumably both fall off at $1/r^2$, and I'm also assuming there's no catastrophic mutual annihilation as with antimatter). So. "totally uncharged" is obviously a consistent option. Are there any nonzero magnitudes for charged gravity that would be consistent with observations? Probably more importantly for physics, but less important from a personal-interest perspective, how would we test this? Or, if this has already been disproved elsewhere, what experiments have we performed to rule this out? *For experimentally confirmed values of "lots", ideally | Negative Mass and gravitation Since Newtonian gravity is analogous to electrostatics shouldn't there be something called negative mass? Also, a moving charge generates electric field, but why doesn't a moving mass generate some other field? | What role does "spontaneously symmetry breaking" played in the "Higgs Mechanism"? In talking about Higgs mechanism, the first part is always some introduction to the concept of spontaneously symmetry breaking (SSB), some people saying that Higgs mechanism is the results of SSB of local gauge symmetry, some people says that we can formulate Higgs mechanism in a gauge invariant way, some people also says that we need only a non-zero vaccum expectation value... I am confused about this different or maybe same point of views. In this post: , the most highly voted answer, I still can't feel how SSB worked in Higgs mechanism. It seem that the validity of last part, the appearance of a mass term for $A$, is guaranteed if we have a non-zero equilibrium value $\phi_0$ to expand around. I do not see that the requirement that the phase of the field $\phi$ need to be fixed at some particular value to generate mass term. Thus it seems to me it is not true that SSB is really indispensable for Higgs mechanism. To put it simply: The spontanously breaking of what is attributed to Higgs mechanism? local gauge symmetry global symmetry, since breaking of a "gauge symmetry" should not have any effect on physics. In higgs mechanism, the really broken symmetry is a global one. Mathematically, it is similar in looking as fixing a gauge, but one should not think it as a spontanously breakdown of local gauge symmetry. other. Is SSB really indispensable for Higgs mechanism? yes, Higgs mechanism is relied on the SSB of some symmetry (above question), the other approches of description eventually has spontanously broke some symmetry. No, the SSB is just one way to describe Higgs mechanism (or even not a complete way), what is really need is the non-zero vaccum expectation value, for example in the linked post the requirement for the mass term to occur is to have some non-zero expectation value of $\phi$ to expand around, we do not need the phase of the field to be fixed, thus the symmetry is not broken. Other. some reference materials: States that SSB of local gauge symmetry is impossible. in the abstract states that: gauge symmetries merely reflect a redundancy in the state description and therefore the spontaneous breaking can not be an essential ingredient. Indeed, as already shown by Higgs and Kibble, the mechanism can be explained in terms of gauge invariant variables, without invoking spontaneous symmetry breaking In the introduction it says: In particular, we emphasize that global U(1) phase rotation symmetry, and not gauge symmetry, is spontaneously violated, and show that the BCS wave function is, contrary to claims in the literature, fully gauge invariant | eng_Latn | 26,967 |
I have seen some articles talking about the role of sigma meson in nuclear force, but more articles omit it and only mention pion, rho and omega (e.g., Wikipedia). What is this sigma meson? | At one point, I decided to make friends with the low-lying spectrum of QCD. By this I do not mean the symmetry numbers (the "quark content"), but the actual dynamics, some insight. The pions are the sloshing of the up-down condensate, and the other pseudoscalars by extending to strangeness. Their couplings are by soft-particle theorems. The eta-prime is their frustrated friend, weighed down by the instanton fluid. The rho and omega are the gauge fields for flavor SU(2), and A1(1260) gauges the axial SU(2), and they have KaluzaKlein-like echoes at higher energies, these can decay into the appropriate "charged" hadrons with couplings that depend on the flavor symmetry multiplet. The proton and the neutron are the topological defects. That accounts for everything up to 1300 but a few scalars and the b1. There are scalars starting at around 1300 MeV which are probably some combination of glue-condensate sloshing around and quark-condensate sloshing around, some kind of sound in the vacuum glue. Their mass is large, their lifetime is not that big, they have sharp decay properties. On the other hand, there is nothing in AdS/QCD which should correspond to the sigma/f0(600), or (what seems to be) its strange counterpart f0(980). While looking around, I found this discussion: . The literature that it pointed to suggests that the sigma is a very unstable bound state of pions (or, if you like, tetraquarks). gives strong evidence for an actual pole; gives a more cursory review. The location of the pole is far away from the real axis, the width is larger than the mass by 20% or so, and the mass is about 400MeV. The authors though are confident that it is real because they tell me that the interpolation the interactions of pions is safe in this region because their goldstone properties dominate the interactions. I want to believe it, but how can you be sure? I know this particle was controversial. I want to understand what kind of picture this is giving. The dispersion subtraction process is hard for me to visualize in terms of effective fields, and the result is saying that there is an unstable bound state. Is there a physical picture of the sigma which is more field theoretical, perhaps even just an effective potential for pions? Did anyone who convinced himself of the reality of the sigma have a way of understanding the bound state properties? Is there an analog unstable bound state for other goldstone bosons? Any insight would be welcome. | Take a sponge ball and compress it. The net force acting on the body is zero and the body isn't displaced. So can we conclude that there is no work done on the ball? | eng_Latn | 26,968 |
Are the intermediate vector bosons real (like the electrons) or just mathetical constructs?i have got a theory to unify the 4 forces, but it does not tell anything about exchange particles in case of the weak force.I could proceed only if they are imaginary. | W and Z bosons are observed/discovered. But as force carrying bosons they should be virtual particles, unobservable? And also they require to have mass, but if they are virtual they may be off-shell, so are they virtual or not. | (used to show two posts from MSE) (there used to be a list of the accounts) (it was there) seems to be fixed | eng_Latn | 26,969 |
are hypothetical, real (non-virtual) particles made up of gluons, the particle of the gluon field that interacts with quarks. The gluons have a color charge themselves and they can form a bound state (the ball). According to lattice computations in Quantum Chromodynamics, they have a mass that varies from . This mean that a bound state of massless particles can form a massive particle. Is the mass of the glueball non-zero only because the constituting gluons interact strongly? Don't massless particles stay massless, even when they form a bound state? Has the glueball a velocity less than c, while the gluons themselves speed with c (which would mean that it has mass)? | From Glueballs are predicted by quantum chromodynamics to be massive, notwithstanding the fact that gluons themselves have zero rest mass in the Standard Model. Glueballs with all four possible combinations of quantum numbers P (parity) and C (c-parity) for every possible total angular momentum have been considered, producing at least fifteen possible glueball states including excited glueball states that share the same quantum numbers but have differing masses with the lightest states having masses as low as 1.4 GeV/c2 (for a glueball with quantum numbers J=0, P=+, C=+), and the heaviest states having masses as great as almost 5 GeV/c2 (for a glueball with quantum numbers J=0, P=+, C=-). Rather than going through a list of possible mechanisms that unfortunately I know next to nothing about, such as can the mass be attributed to virtual quarks, or binding energy between the gluons, I would rather leave the question as in the title to find out as much as I can. Also, although the SM is firmly established, would the discovery of Glueballs buttress it further? My apologies for not knowing more about the interior of hadron like particles or if the answer is readily available (or worse, blindingly obvious). | The entire site is blank right now. The header and footer are shown, but no questions. | eng_Latn | 26,970 |
How can a truly elementary particle decay into other particles? Consider (for example) the next particle decays: The decay of a Higgs and the decay of a muon [in the diagram of which we also see the decay of (virtual) $W^-$ into an electron and its associated neutrino)]. If a particle (or an excitation of the associated quantum field) is truly elementary doesn't that imply that it can't change into other particles? The case of a muon (which is considered elementary, i.e. not built up out of other particles) changing into an electron, and two neutrinos (which are all three also considered to be elementary) can very easily be described in the of Haim Harari (of which I'm a big fan), in which only two (!) truly elementary (apart from the photon, gluon and the $Z^0$ and $W^{+/-}$, of which the last three are considered to be composed particles which transmit not a truly elementary force, but a residual force of a deeper force, as once the $\eta$ was thought to be the transmitter of the strong force, which turned out to be the residual force of the strong force as it is known today) particles are said to exist: the T- and V-rishon (and their anti-particles). $\bar T\bar T\bar T$ (the muon, in this model considered as an excited state of the electron) gives a $VVV$ (neutrino), $\bar V\bar V\bar V$ (the anti-neutrino, associated with the electron), and a $\bar T\bar T\bar T$ (the electron). So before and after the change, the same (net) combination of rishons exists. The virtual $W^-$ is a short existent $\bar V\bar V\bar V\bar T\bar T\bar T$ combination, which in the rishon model obviously has an electric charge -1 because the $T$-rishon has electric charge +1, and the $V$-rishon has no electric charge. In this change, the (according to the rishon model) truly elementary particles keep their identity, so a $T$-rishon can't change into a $V$-rishon and vice-versa, and it only seems that what we consider elementary particles can change into other elementary particles. The decays, in the rishon model, are nothing more than rearrangements of T-rishons and V-rishons (and their antiparticles), while at the same time virtual $T$ and $V$ rishons can become real in the decay and contribute to the process. Clearly, these $T$ and $V$ rishons can't change their identity if they are truly elementary (if so that would indicate that these two elementary particles would be composed of even more elementary particles, which is nonsense if you need only two elementary particles to explain the abundance of quarks and leptons; the model doesn't address the force-carrying particles, which are all massless in this model). In the case of the changing Higgs (which in the rishon model isn't needed to give mass to particles, but it nevertheless exists because it has been detected so it can be considered as a boson particle), the change results in two pairs of $TTT$ and $\bar T\bar T\bar T$ combinations of T-rishons (and their anti-particles), the electron and it's anti-particle and a muon together with its anti-particle. The two $Z^0$ particles that appear shortly are both $TTT\bar T\bar T\bar T$ combinations (with obvious electric charges of zero). So the Higgs can be a combination of six $T$-rishons and six $\bar T$-rishons. Again the truly elementary particles (the $T$ and the $V$) don't change their identity. So does the fact that what we consider as elementary particles (excitations of the associated field) can change into other particles mean they are not truly elementary? | Why do physicists think that the electron is an elementary particle? When we first discovered the proton and neutron, I'm sure scientists didn't think that it was made up of quark arrangements, but then we figured they could be and experiments proved that they were. So, what is it about the electron that leads us to believe that it isn't a composite particle? What evidence do we have to suggest that it it isn't? | Do the laws of physics evolve? Hubble's constant $a(t)$ appears to be changing over time. The fine stucture constant $\alpha$, like many others in QFT, is a running constant that varies, proportional to energy being used to measure it. Therefore, it could be agued that all running constants have 'evolved' over time as the Universe has expanded and cooled. Both the local and global curvature of the Universe changes over time implying that so too does the numerical value of $\pi$. All these things are however constants (well, let's say parameters since they are not really 'constant'.) In with astronomer Sir Fred Hoyle, Feynman said "what today, do we not consider to be part of physics, that may ultimately become part of physics?" He then goes on to say "..it's interesting that in many other sciences there's a historical question, like in geology - the question how did the Earth evolve into the present condition? In biology - how did the various species evolve to get to be the way they are? But the one field that hasn't admitted any evolutionary question - is physics." So have the laws of physics remained form-invariant over the liftetime of the Universe? Does the recent understanding of the aforementioned not-so-constant constants somehow filter into the actual form of the equations being used? Has advances in astronomical observations, enabling us to peer back in time as far back as the CMB, given us any evidence to suggest that the laws of nature have evolved? If Feynman thinks that "It might turn out that they're not the same all the time and that there is a historical, evolutionary question." then this is surely a question worth asking. NB/ To be clear: this is a question concerning purely physics, whether the equations therein change as the Universe ages, and whether there is any observational evidence for this. It is not intended as an oportunity for a philosophical discussion. | eng_Latn | 26,971 |
Why is particle superposition still part of quantum mechanics? After reading an article on Schrodinger's Cat, it seems that if we take the environment as an observer, that superposition cannot occur because all atomic and subatomic entities would be observed all the time. Thus, something like quantum entanglement cannot occur. So if superposition cannot occur, why is superposition (and by extension quantum entanglement) still part of quantum mechanics? Updated: In the question , the notion of observer is replaced by measurement. In this context, my question would be: if the system (cat) is constantly being measured by the environment (the observer is watching the cat), how can superposition (the cat is in multiple states; i.e., alive and dead) exist in quantum mechanics? For example, if a photon passes by a heavy particle and splits into an electron and positron, the splitting process is a measurement of the electron and positron to make sure the total spin is 0. I understand the argument that we might not know which has +1/2 and which has -1/2, but the observation/measurement had to be done to make sure we didn't have 3/4 total spin. | How is it possible that quantum phenomenons (e.g. superposition) are possible when all quantum particles are being constantly observed? I don't understand how quantum mechanics (and therefore also quantum computers) can work given that while we work with quantum states, particles that this quantum state consist of cannot be observed, which is the most fundamental requirement. If I am not mistaken, by "observed" we mean interaction with any other particle (photon, gluon, electron or whatever else). So my very important questions: Aren't the particles this quantum state consists of interacting with each other? Why doesn't that cause the state to collapse? Aren't all particles in the universe interacting with Higgs field and gravitons etc? Why doesn't that cause every quantum state to collapse? I feel there is something very fundamental in quantum mechanics that I am not aware of, hence I would be very pleased to have these questions answered. | What's the deepest reason why QCD bound states have integer charge? What's the deepest reason why QCD bound states have integer electric charge, i.e. equal to an integer times the electron charge? Given that the quarks have the fractional electric charges they do, this is a consequence of color confinement. The charges of the quarks are constrained in the context of the standard model by anomaly cancellation, and can be explained by grand unification. The GUT explanation for the charges doesn't care about the bound state spectrum of the QCD sector, so it just seems to be a coincidence that hadrons (which are composite) have integer charge, and that leptons (which are elementary) also have integer charge. Now maybe there's some anthropic argument for why such a coincidence is useful (in the case of proton and electron, it gives us atoms as we know them). Or maybe you can argue that GUTs naturally produce fractionally charged particles and strongly coupled sectors, and it's just not much of a coincidence. But I remain curious as to whether Seiberg duality, anyons, some UV/IR relationship... could really produce something like the lepton-hadron charge coincidence, for deeper reasons. I suppose one is looking for a theory in which properties of bound states in one sector have a direct and nontrivial relationship to properties of elementary states in another sector. Is there anything like this out there? (This question was prompted by muster-mark's many recent questions about fractional charge, and by a that the hadron-lepton charge coincidence is a "semi-coincidence", which assured me that I wasn't overlooking some obvious explanation.) | eng_Latn | 26,972 |
Symmetry of physical laws What is the easiest explanation for how the symmetry of laws under translation in time relates to energy conservation in physics? | Emmy Noether's theorem in simpler terms I'd like to understand and its contents as to what it implies in a bit simpler terms. I am familiar with mathematics unto Calculus 1,2,3 and some linear algebra and group theory. I am familiar with that for each symmetry there is a conservation law. Now is there a one-one correspondence between these two always? What about laws like conservation of charge? And conservation of energy? And conservation of mass? Considering our view of nature was changed as Special Relativity was introduced and thus, what earlier the theorem would have asserted as mass and energy to be originating from different symmetries then how did we reconcile these two as just one symmetry? | What do the supercharges in extended supersymmetry do? What do the supercharges in do? In ${\cal N}=1$ supersymmetry there are a certain number of fermions and and equal number of bosons. You can transform all fermions to the bosons (and vice versa) in a 1 to 1 fashion using a single supercharge, $Q$. So what happens when you have, for example, ${\cal N}=2$ supersymmetry with 8 supercharges? Since $Q$ is a generator of supersymmetry transformations, is it a linear combination of these supercharges that act on the particles? In which case could one particle be acted on by two separate linear combinations of $Q$? Or is it strictly one linear combination of $Q$ per fermion/boson? Also, what does ${\cal N}$ mean physically? What difference does ${\cal N}=2$ have to ${\cal N}=1$ other than more supercharges? Or is that the only difference between the two theories? | eng_Latn | 26,973 |
Quantum mechanics not in $L_2$-space As far as I understand the postulates of quantum mechanics use only properties of abstract Hilbert space. So could we use any other Hilbert space for calculations instead of $L_2$? What could it be? I can only suggest infinite-dimensional vector space with Euclidean norm, but it seems to be isomorphic to $L_2$. | Why we use $L_2$ Space In QM? I asked this question for many people/professors without getting a sufficient answer, why in QM Lebesgue spaces of second degree are assumed to be the one that corresponds to the Hilbert vector space of state functions, from where this arises? and why 2-order space that assumes the following inner product: $\langle\phi|\psi\rangle =\int\phi^{*}\psi\,dx$ While there is many ways to define the inner product. In Physics books, this always assumed as given, never explains it, also I tried to read some abstract math books on this things, and found some concepts like "Metric weight" that will be minimized in such spaces, even so I don't really understand what is behind that, so why $L_2$? what special about them? Who and how physicists understood that those are the one we need to use? | What's the deepest reason why QCD bound states have integer charge? What's the deepest reason why QCD bound states have integer electric charge, i.e. equal to an integer times the electron charge? Given that the quarks have the fractional electric charges they do, this is a consequence of color confinement. The charges of the quarks are constrained in the context of the standard model by anomaly cancellation, and can be explained by grand unification. The GUT explanation for the charges doesn't care about the bound state spectrum of the QCD sector, so it just seems to be a coincidence that hadrons (which are composite) have integer charge, and that leptons (which are elementary) also have integer charge. Now maybe there's some anthropic argument for why such a coincidence is useful (in the case of proton and electron, it gives us atoms as we know them). Or maybe you can argue that GUTs naturally produce fractionally charged particles and strongly coupled sectors, and it's just not much of a coincidence. But I remain curious as to whether Seiberg duality, anyons, some UV/IR relationship... could really produce something like the lepton-hadron charge coincidence, for deeper reasons. I suppose one is looking for a theory in which properties of bound states in one sector have a direct and nontrivial relationship to properties of elementary states in another sector. Is there anything like this out there? (This question was prompted by muster-mark's many recent questions about fractional charge, and by a that the hadron-lepton charge coincidence is a "semi-coincidence", which assured me that I wasn't overlooking some obvious explanation.) | eng_Latn | 26,974 |
Why is this decay process allowed? I have been given an assignment in which I have been asked to list some quantum numbers for some given allowed processes. One of them is $\Delta^+ \rightarrow p^+ + \pi^0$ I know that $\Delta^+$ has J value as 3/2, $p^+$ has J value as 1/2 and $\pi^0$ has J value as 0. So, clearly, the total angular momentum is not conserved. Then, why is this process allowed? | How does Delta baryon decay conserve angular momentum? I'm a chemist so bear with me: I understand the $\Delta^{+}$ and $\Delta^{0}$ to be in some sense spin (and isospin) quartet states of the proton and neutron. These can decay straight to a proton or neutron through emission of a pion, which is spin-0. I've been puzzling about the mechanism by which this decay conserves spin. I note via Wikipedia that into either a lepton pair or a photon pair, for which it's easy to show spin is conserved, however pion production seems to induce a loss of $J=1$. This seems to suggest momenta of: $\Delta^{+} (J=\frac{3}{2}) \rightarrow{} p^{+} (J=\frac{1}{2}) + \pi^{0} (J=0)$ Am I missing a boson? Is my understanding of spin flawed? I assume that if this decay exists, similar things turn up everywhere else. | Definition of the $Q$ factor? According to Wikipedia, the is defined as: $$Q=2\pi\frac{\mathrm{energy \, \, stored}}{\mathrm{energy \, \,dissipated \, \, per \, \, cycle}}.$$ Here are my questions: Does the energy dissipated per cycle assume that the amplitude is constant from one cycle to the next. Is it always calculated at the resonance frequency? If the answer to 2 is yes can you explain why for a forced oscillator system with a damping coefficient of $\gamma$ and natural frequency $\omega_o$ the quality factor is $Q=\omega_o/\gamma$ and not some more complicated expression involving the actual resonant frequency (which is not quite $\omega_o$ and is given by $$\omega_r=(\omega_0^2-\frac{\gamma^2}{2})^{\frac{1}{2}}$$ of the system? Is this just an approximation i.e. are we assuming that it resonates at $\omega_o$ but in fact the actual expression is a big more complicated? Edit: With using the actual value of $\omega_r$ I get: $Q=(\omega_0^2-\frac{\gamma^2}{2})^{\frac{1}{2}}/\gamma$ is this more correct? | eng_Latn | 26,975 |
How do force carrying particles "give" force? So, I am not taking physics in school, but I do have an interest in it, and I was wondering, in the standard model, all of the force carrying particles (photons, Z Bosons, W Bosons, gluons, and (hypothetical) gravitons) give a separate type of force. Those being the electromagnetic force, the weak nuclear force, the strong nuclear force and gravity. What my question is, is how do these particles give their force and why do they give different forces? What differences are between the particles that they give different forces? For example why does a photon give the electromagnetic force while a gluon gives the strong nuclear force? I am not asking why particles carry force, I am asking about how they give that force to other particles. | The exchange of photons gives rise to the electromagnetic force Pardon me for my stubborn classical/semiclassical brain. But I bet I am not the only one finding such description confusing. If EM force is caused by the exchange of photons, does that mean only when there are photons exchanged shall there be a force? To my knowledge, once charged particles are placed, the electromagnetic force is always there, uninterruptedly. According to such logic, there has to be a stream of infinite photons to build EM force, and there has to be no interval between one "exchange event" to another. A free light source from an EM field? The scenario is really hard to imagine. For nuclei the scenario becomes even odder. The strong interaction between protons is caused by the exchange of massive pions. It sounds like the protons toss a stream of balls to one another to build an attractive force - and the balls should come from nothing. Please correct me if I am wrong: the excitations of photons and pions all come from nothing. So there should be EM force and strong force everywhere, no matter what type of particles out there. Say, even electrical neutral, dipole-free particles can build EM force in-between. And I find no reason such exchanges of particles cannot happen in vacuum. Hope there will be some decent firmware to refresh my classical brain with newer field language codes. | Is the density operator a mathematical convenience or a 'fundamental' aspect of quantum mechanics? In quantum mechanics, one makes the distinction between mixed states and pure states. A classic example of a mixed state is a beam of photons in which 50% have spin in the positive $z$-direction and 50% have spin in the positive $x$-direction. Note that this is not the same as a beam of photons, 100% of which are in the state $$ \frac{1}{\sqrt{2}}[\lvert z,+\rangle + \lvert x,+\rangle]. $$ It seems, however, that at least in principle, we could describe this beam of particles as a single pure state in a 'very large' Hilbert space, namely the Hilbert space that is the tensor product of all the $\sim 10^{23}$ particles (I think that's the proper order of magnitude at least). So then, is the density operator a mathematical convenience, or are there other aspects of quantum mechanics that truly require the density operator to be a 'fundamental' object of the theory? (If what I mean by this is at all unclear, please let me know in the comments, and I will do my best to clarify.) | eng_Latn | 26,976 |
Why aren't quarks free? According to latest modern theory on subatomic particles, electrons and protons are further divided into quarks, having fractional charges. My question is, why can't they exist independently? and why don't they show up Millikan's experiment? | About free quarks and confinement I simply know that a single free quark does not exist. What is the reason that we can not get a free quark? If we can't get a free quark then what is single-top-quark? | What makes a Feynman diagram real or virtual? Simple question: as the title says, what makes a real Feynman diagram real, and what makes a virtual diagram virtual? Or in other words, how do I tell whether any given diagram is real or virtual? I've never gotten a really satisfying explanation of this. I would imagine it has something to do with virtual particles, but all internal propagators are virtual particles and I know for a fact that having internal lines doesn't make a diagram virtual. | eng_Latn | 26,977 |
Supersymmetry with two independent supercharges, $\mathcal N=4$, or $\mathcal N=(2,2)$, and physical significance? My question is about a specific example of supersymmetry in quantum mechanics. I am not an expert on SUSY, and I would like to have some insights on this. Imagine you have a non-Hermitian supercharge $Q$ satisfying the algebra \begin{equation} \{ P, Q \}=0,\,\,\,\, Q^2=( Q^\dagger)^2=0, \,\,\, \{Q,Q^\dagger\}=H, \end{equation} where $P$ is the parity operator and $H$ is the Hamiltonian. To be specific, let's assume that $H$ is a quantum mechanical Hamiltonian (e.g., Schrödinger) in one dimension. In this case, since the supercharge is not-Hermitian and can be written as a sum of two Hermitian operators, one says that the Hamiltonian has $\mathcal N=2$ supersymmetry. Imagine now that one has a second supercharge $Q'$ such that $[Q,Q']\neq0$ and $\{Q,Q'\}\neq0$, satisfying the same algebra \begin{equation} \{ P, Q' \}=0,\,\,\,\, Q^{\prime 2}=(Q^{\prime\dagger})^2=0, \,\,\, \{Q',Q^{\prime\dagger}\}=H, \end{equation} My question(s): In this case, one is talking about $\mathcal N=4$, $\mathcal N=(2,2)$ or else? What is the physical significance of supersymmetry with respect to two independent supercharges? | What do the supercharges in extended supersymmetry do? What do the supercharges in do? In ${\cal N}=1$ supersymmetry there are a certain number of fermions and and equal number of bosons. You can transform all fermions to the bosons (and vice versa) in a 1 to 1 fashion using a single supercharge, $Q$. So what happens when you have, for example, ${\cal N}=2$ supersymmetry with 8 supercharges? Since $Q$ is a generator of supersymmetry transformations, is it a linear combination of these supercharges that act on the particles? In which case could one particle be acted on by two separate linear combinations of $Q$? Or is it strictly one linear combination of $Q$ per fermion/boson? Also, what does ${\cal N}$ mean physically? What difference does ${\cal N}=2$ have to ${\cal N}=1$ other than more supercharges? Or is that the only difference between the two theories? | What role does "spontaneously symmetry breaking" played in the "Higgs Mechanism"? In talking about Higgs mechanism, the first part is always some introduction to the concept of spontaneously symmetry breaking (SSB), some people saying that Higgs mechanism is the results of SSB of local gauge symmetry, some people says that we can formulate Higgs mechanism in a gauge invariant way, some people also says that we need only a non-zero vaccum expectation value... I am confused about this different or maybe same point of views. In this post: , the most highly voted answer, I still can't feel how SSB worked in Higgs mechanism. It seem that the validity of last part, the appearance of a mass term for $A$, is guaranteed if we have a non-zero equilibrium value $\phi_0$ to expand around. I do not see that the requirement that the phase of the field $\phi$ need to be fixed at some particular value to generate mass term. Thus it seems to me it is not true that SSB is really indispensable for Higgs mechanism. To put it simply: The spontanously breaking of what is attributed to Higgs mechanism? local gauge symmetry global symmetry, since breaking of a "gauge symmetry" should not have any effect on physics. In higgs mechanism, the really broken symmetry is a global one. Mathematically, it is similar in looking as fixing a gauge, but one should not think it as a spontanously breakdown of local gauge symmetry. other. Is SSB really indispensable for Higgs mechanism? yes, Higgs mechanism is relied on the SSB of some symmetry (above question), the other approches of description eventually has spontanously broke some symmetry. No, the SSB is just one way to describe Higgs mechanism (or even not a complete way), what is really need is the non-zero vaccum expectation value, for example in the linked post the requirement for the mass term to occur is to have some non-zero expectation value of $\phi$ to expand around, we do not need the phase of the field to be fixed, thus the symmetry is not broken. Other. some reference materials: States that SSB of local gauge symmetry is impossible. in the abstract states that: gauge symmetries merely reflect a redundancy in the state description and therefore the spontaneous breaking can not be an essential ingredient. Indeed, as already shown by Higgs and Kibble, the mechanism can be explained in terms of gauge invariant variables, without invoking spontaneous symmetry breaking In the introduction it says: In particular, we emphasize that global U(1) phase rotation symmetry, and not gauge symmetry, is spontaneously violated, and show that the BCS wave function is, contrary to claims in the literature, fully gauge invariant | eng_Latn | 26,978 |
Energy conservation Hamiltonian dependency Suppose the a system has a Hamiltonian $H = H(q,p)$, and suppose $H$ does not depend explicitly on time. If $H\neq E$ the total energy of the system, does this necessarily say that $E$ is not conserved? Why? | Example where Hamiltonian $H \neq T+V=E$, but $E=T+V$ is conserved I'm looking for an example of a Hamiltonian $H$, where $H\neq T+V$, but the total energy in the system, $E=T+V$, is still conserved. While I'm at it, I might as well add that I'd be most interested in an example from a classical field theory. Furthermore, I am looking for a nontrivial example, e.g. where $H$ doesn't just differ from $E$ by some gradient function that integrates to 0 in the action. In particular, I am trying to get a better understanding of the physical implications of $H$ being conserved when nontrivial variables are used, i.e. physically, what does $H$ this correspond to. Conversely, can one have a system where $E = H$ in one frame, and is conserved, while in another frame $E'\neq H'$, and $H'$ is conserved while $E'$ is not? | Do neutrinos not couple to the Higgs field? I was reading the CernCourier, my favorite source of message on Higgs and friends. I was rather shocked, when I saw this: "The mechanism by which neutrino mass is generated is not known." What? Not known? says: In Higgs-based theories, the property of 'mass' is a manifestation of potential energy transferred to particles when they interact ("couple") with the Higgs field, which had contained that mass in the form of energy. Does this mean that neutrinos don't couple to the Higgs field? | eng_Latn | 26,979 |
Do we already know some problems, that would be hard to solve for quantum computers, and use them in cryptography? I was wondering, whether there are any problems that we already know are difficult to solve for a quantum computer, and that we could potentially use in cryptography, just as we do now with e.g. the factorization of integers? | Is it possible for an encryption method to exist which is impossible to crack, even using quantum computers? Quantum computers are known to be able to crack a broad range of cryptographic algorithms which were previously thought to be solvable only by resources increasing exponentially with the bit size of the key. An example for that is . But, as far I know, not all problems fall into this category. On , we can read Researchers have developed a computer algorithm that doesn’t solve problems but instead creates them for the purpose of evaluating quantum computers. Can we still expect a new cryptographic algorithm which will be hard to crack using even a quantum computer? For clarity: the question refers to specifically to the design of new algorithms. | What's the deepest reason why QCD bound states have integer charge? What's the deepest reason why QCD bound states have integer electric charge, i.e. equal to an integer times the electron charge? Given that the quarks have the fractional electric charges they do, this is a consequence of color confinement. The charges of the quarks are constrained in the context of the standard model by anomaly cancellation, and can be explained by grand unification. The GUT explanation for the charges doesn't care about the bound state spectrum of the QCD sector, so it just seems to be a coincidence that hadrons (which are composite) have integer charge, and that leptons (which are elementary) also have integer charge. Now maybe there's some anthropic argument for why such a coincidence is useful (in the case of proton and electron, it gives us atoms as we know them). Or maybe you can argue that GUTs naturally produce fractionally charged particles and strongly coupled sectors, and it's just not much of a coincidence. But I remain curious as to whether Seiberg duality, anyons, some UV/IR relationship... could really produce something like the lepton-hadron charge coincidence, for deeper reasons. I suppose one is looking for a theory in which properties of bound states in one sector have a direct and nontrivial relationship to properties of elementary states in another sector. Is there anything like this out there? (This question was prompted by muster-mark's many recent questions about fractional charge, and by a that the hadron-lepton charge coincidence is a "semi-coincidence", which assured me that I wasn't overlooking some obvious explanation.) | eng_Latn | 26,980 |
Antiparticles as "holes" of the quantum fields? If particles are simply regions of space where certain quantum fields have non-zero divergence, are anti-particles simply the corresponding regions of opposite divergence? This seems like the intuitive answer, especially when considering the process of annihilation. I have heard before that anti-particles are analogous to particles moving through time in reverse, which seems to indicate that an annihilation event is just a point of symmetry in that (arguably, single) particle's history. This analogy breaks down, however, when it comes to gravitation, since there seems to be no evidence of a negative-mass particle. So what then is the meaning of an anti-particle, when their symmetry is preserved across certain fields, but not other? | Are antiparticles just particle-shaped holes? If particles are simply regions of space where certain quantum fields have non-zero divergence, are anti-particles simply the corresponding regions of opposite divergence? This seems like the intuitive answer, especially when considering the process of annihilation. I have heard before that anti-particles are analogous to particles moving through time in reverse, which seems to indicate that an annihilation event is just a point of symmetry in that (arguably, single) particle's history. This analogy breaks down, however, when it comes to gravitation, since there seems to be no evidence of a negative-mass particle. So what then is the meaning of an anti-particle, when their symmetry is preserved across certain fields, but not other? | Renormalized mass I am reading Schwarz QFT and I reached the mass renormalization part. So he introduces, after renormalization, a physical mass, defined as the pole of the renormalized propagator, and a renormalized mass which can be the physical mass, but can also take other values, depending on the subtraction schemes used. Are these masses, other than the physical one, observable in any way experimentally, or are they just ways to do the math easier (using minimal subtraction instead of on-shell scheme, for example)? Also, in the case of charge renormalization, the explanation was that due to the vacuum polarization, the closer you are to the charge, the more you see of it, so the charge of the particle increases with the momentum you are testing the particle with. However, I am not sure I understand, from a physical point of view, why do you need to renormalize the mass. Is this physical mass (defined as the pole of the renormalized propagator) the same no matter how close you get, or it also changes with energy? And if it changes, what is shielding it at big distances? | eng_Latn | 26,981 |
Can antimatter becomes black hole? I know it seems unlikely to accumulate sufficient amount of antimatter to let it collapse under its own weight to become a black hole(maybe the gravity works differently I don't know) since they will definitely react aggressively with ordinary matter which made up most of our known universe producing energy. My question is can we accelerate antimatters and then let them collide with enough energy to produce a tiny black hole? would this tiny black hole shares similar properties with its normal counterparts? Oops I almost forgot what kind of particles are produced in the abovementioned collision? (e.g. antiproton-antiproton) | Anti-Matter Black Holes Assuming for a second that there were a pocket of anti matter somewhere sufficiently large to form all the type of object we can see forming from normal matter - then one of these objects would be a black hole. Question is, would there be a difference between an anti matter black hole and a normal matter black hole - in terms of how would the matter/anti-matter make the black hole different, or would they be the same? I would expect the answer to be that the black hole formed from anti matter would retain the anti-matter properties in such a way that if it was to merge with a black hole at same size formed from normal matter that they would annihilate each other con convert into pure energy - Would that be a correct understanding? | What happens to matter in a standard model with zero Higgs VEV? Suppose you reset the parameters of the standard model so that the Higgs field average value is zero in the vacuum, what would happen to standard matter? If the fundamental fermions go from a finite to a zero rest mass, I'm pretty sure that the electrons would fly away from nuclei at the speed of light, leaving positively charged nuclei trying to get away from each other. Looking at the solution for the Hydrogen atom, I don't see how it would be possible to have atoms with zero rest mass electrons. What happens to protons and neutrons? Since only a very small part of the mass of protons and neutrons is the rest mass of the quarks, and since they're flying around in there at relativistic speeds already, and since the nuclear force is so much stronger than the electrical force with an incredible aversion to naked color, would protons and neutrons remain bound assemblages of quarks and virtual gluons? Would they get a little larger? A little less massive? What would happen to nuclei? Would they stay together? If the protons and neutrons hold together and their properties change only some, then I might expect the same of nuclei. Different stable isotopes, different sizes, and different masses, but I would expect there would still be nuclei. Also the W and Z particles go to zero rest mass. What does that do to the electroweak interactions? Does that affect normal stable matter (outside of nuclear decay modes)? Is the weak force no longer weak? What happens to the forces overall? | eng_Latn | 26,982 |
What is the basis of description of matter and energy in our universe in the form of wave and particle? What exactly does wave particle duality mean does it mean that an electron is a particle which is moving like a wave or does it mean that an electron and a photon is neither a wave nor a particle and something completely different or is it as if it’s sometimes a wave and the other times a particle or if it’s both simultaneously? Similarly for photons. (Is it like mass is nothing but compactly packed energy and similarly for energy, as in $E=mc^2$, which is described by wave particle duality as in the answer to the first question?) Based on what have we got the two ideas of wave and particle? That is, how have we-on what basis, classified the behaviour of matter and energy as wave and particle? (Like we have classified matter into solid, liquid, gas, Bose-Einstein condensate and plasma based broadly on the inter particle forces of attraction, how is matter packed, the relative energies etc.) | Is the wave-particle duality a real duality? I often hear about the wave-particle duality, and how particles exhibit properties of both particles and waves. However, I wonder, is this actually a duality? At the most fundamental level, we 'know' that everything is made up out of particles, whether those are photons, electrons, or maybe even strings. That light for example, also shows wave-like properties, why does that even matter? Don't we know that everything is made up of particles? In other words, wasn't Young wrong and Newton right, instead of them both being right? | Why mass terms are forbidden? I would like to clarify my understanding on why mass terms in Lagrangians of gauge theories are forbidden. It's often repeated that particle masses are forbidden by electroweak symmetry because it is a chiral theory. I want to make a distinction between fermionic masses and gauge boson masses. Looking through the transformations of gauge boson mass terms, it seems that these are in fact always forbidden by their respective gauge symmetry. Is this correct? (So if there was no SU(2) symmetry, the photon and gluon would still need to be massless?) In which case, the electroweak symmetry is actually responsible for forbidding all other mass terms (i.e. weak boson masses and fermion masses) due to the usual chiral arguments. Is this correct? | eng_Latn | 26,983 |
Is Coulomb's law correct? Why don't electrons and protons collide? Hydrogen atoms are often ionized. After ionization, it is divided into electrons and protons, which can merge into hydrogen atoms at any time. Why don't electrons crash on protons? According to Coulomb's law, when they are getting closer, they attract more and more. One of the most possible choices is to crash. This is not a duplicated question. Because instead of talking about the structure of atoms (why electrons don't crash nuclei), we're talking about why they don't merge together because of the Coulomb attraction when electrons are close to protons. | Why don't electrons crash into the nuclei they "orbit"? I'm having trouble understanding the simple "planetary" model of the atom that I'm being taught in my basic chemistry course. In particular, I can't see how a negatively charged electron can stay in "orbit" around a positively charged nucleus. Even if the electron actually orbits the nucleus, wouldn't that orbit eventually decay? I can't reconcile the rapidly moving electrons required by the planetary model with the way atoms are described as forming bonds. If electrons are zooming around in orbits, how do they suddenly "stop" to form bonds. I understand that certain aspects of quantum mechanics to address these problems, and that there are of atoms. My question here is whether the planetary model itself addresses these concerns in some way (that I'm missing) and whether I'm right to be uncomfortable with it. | What happens to matter in a standard model with zero Higgs VEV? Suppose you reset the parameters of the standard model so that the Higgs field average value is zero in the vacuum, what would happen to standard matter? If the fundamental fermions go from a finite to a zero rest mass, I'm pretty sure that the electrons would fly away from nuclei at the speed of light, leaving positively charged nuclei trying to get away from each other. Looking at the solution for the Hydrogen atom, I don't see how it would be possible to have atoms with zero rest mass electrons. What happens to protons and neutrons? Since only a very small part of the mass of protons and neutrons is the rest mass of the quarks, and since they're flying around in there at relativistic speeds already, and since the nuclear force is so much stronger than the electrical force with an incredible aversion to naked color, would protons and neutrons remain bound assemblages of quarks and virtual gluons? Would they get a little larger? A little less massive? What would happen to nuclei? Would they stay together? If the protons and neutrons hold together and their properties change only some, then I might expect the same of nuclei. Different stable isotopes, different sizes, and different masses, but I would expect there would still be nuclei. Also the W and Z particles go to zero rest mass. What does that do to the electroweak interactions? Does that affect normal stable matter (outside of nuclear decay modes)? Is the weak force no longer weak? What happens to the forces overall? | eng_Latn | 26,984 |
One principle in general relativity is that the wordlines of massless particles are null geodesics. It also seem to be a commonly stated fact (for instance see eq. (3.62) in Section 3.4 of Carroll's GR text) that one can parameterize the worldline of a massless particle as $x(\lambda)$ such that $$\frac{dx^{\mu}}{d\lambda} = p^{\mu}, \tag{1}$$ where $p^{\mu}$ is the four-momentum of the massless particle. To clarify what is meant by four-momentum, the energy of a particle with four-momentum $p$ as measured by an observer moving with four-velocity $U$ is $-p_\mu U^\mu$. Now I understand why one could pick a parameterization that satisfies (1) at a particular point. But why must such a parameterization satisfy (1) globally? The only argument I have is that such a parameterization always exists for the world-line of a particle with mass, and taking the limit to light speed suggests that such a parameterization should also hold for the world-lines of massless particles. My question is: what are some other arguments for why the parameterization should exist? | I am following Carroll's GR book. He explain that it is convention to parameterize geodesics of photons by a parameter $\lambda$ such that $$p^\mu ~=~ \frac{d x^{\mu}}{d \lambda}.\tag{3.62}$$ But this is the definition of 4-velocity for a massive particle in the case of $\lambda=\tau$ equal to proper time. My question then, is $$u^\mu = p^\mu$$ for all massless particles? I ask because it's well-known that proper time $\tau$ freezes for massless particles. | Why massless particles have zero chemical potential? | eng_Latn | 26,985 |
What are the parity of particles? | How is $J^{PC}$ value experimentally determined for new types of particles? | Hair Paricle System not rendering properly on plane | eng_Latn | 26,986 |
if Higgs boson stopped existing, what would happen? | What happens to matter in a standard model with zero Higgs VEV? | Leagues still count association bonus | eng_Latn | 26,987 |
Does the positron prove that Dirac's electron sea must exist? | What was missing in Dirac's argument to come up with the modern interpretation of the positron? | What was missing in Dirac's argument to come up with the modern interpretation of the positron? | eng_Latn | 26,988 |
Is there a reason why every meson and baryon has an integer electric charge? | What's the deepest reason why QCD bound states have integer charge? | Why is the charge naming convention wrong? | eng_Latn | 26,989 |
Why are there no loop corrections to the photon mass? I know that a question about why the photon is massless already exists, however it did not answer this question. First off, I do understand why the photon does neither have a bare mass term due to gauge invariance of the standard model lagrangian nor does it get mass from the Higgs mechanism. However as far as I understood it particles generally can get loop corrections to their mass (e.g. possibly generating neutrino masses). Since I am not really familiar with this mechanism I would like to know why there seem to be no loop corrections to the photon mass. Do they cancel out or am I just missing something obvious. I'd also appreciate a link to a review-paper or book chapter dealing with this. | What prevents photons from getting mass from higher order Feynman diagrams The Higgs boson and gluons have no electric charge and photons couple to charge, so there is no tree level interaction between them and photons. But what prevents higher order diagrams from contributing a non-zero mass term to the photon, for instance where a photon couples to some fermion (say an electron, or a top quark) which can interact with the Higgs field. Or consider that same diagram but with quarks and a gluon interacting between them? Or any higher diagram with even more loops? I have heard charge conservation depends on gauge invariance, which in turn depends on photons being massless. So it appears the photon has no mass, and these diagrams must all cancel somehow. So I'm hoping there is a very nice symmetry explanation for why they all disappear, but if I say "because of gauge invariance" that would be circular logic, so there must be another symmetry at stake here? What prevents photons from obtaining a mass from high-order self-energy loop diagrams? | Is Angular Momentum truly fundamental? This may seem like a slightly trite question, but it is one that has long intrigued me. Since I formally learned classical (Newtonian) mechanics, it has often struck me that angular momentum (and generally rotational dynamics) can be fully derived from normal (linear) momentum and dynamics. Simply by considering circular motion of a point mass and introducing new quantities, it seems one can describe and explain angular momentum fully without any new postulates. In this sense, I am lead to believe only ordinary momentum and dynamics are fundamental to mechanics, with rotational stuff effectively being a corollary. Then at a later point I learned quantum mechanics. Alright, so orbital angular momentum does not really disturb my picture of the origin/fundamentality, but when we consider the concept of spin, this introduces a problem in this proposed (philosophical) understanding. Spin is apparently intrinsic angular momentum; that is, it applies to a point particle. Something can possess angular momentum that is not actually moving/rotating - a concept that does not exist in classical mechanics! Does this imply that angular momentum is in fact a fundamental quantity, intrinsic to the universe in some sense? It somewhat bothers me that that fundamental particles such as electrons and quarks can possess their own angular momentum (spin), when otherwise angular momentum/rotational dynamics would fall out quite naturally from normal (linear) mechanics. There are of course some fringe theories that propose that even these so-called fundamental particles are composite, but at the moment physicists widely accept the concept of intrinsic angular momentum. In any case, can this dilemma be resolved, or do we simply have to extend our framework of fundamental quantities? | eng_Latn | 26,990 |
Use a Delayed Choice Quantum Eraser to communicate Faster Than Light In the , photons reach D0 and shows a pattern, before its quantum entangled counterparts reach one of D1, D2, D3, or D4. The pattern differs based on what happens at the beam splitters (BSa and BSb) and whether the which-path information is lost. What if, instead of installing beam splitters BSa and BSb, we install either pure glass panels or pure silver mirrors. Now imagine we place the splitter part of the setup light-years away from earth, with an astronaut who can decide if she wants to put 2 mirrors or 2 glass panels at BSa and BSb. By shooting photons and observing the patterns on D0 on earth, we could instantly tell which decision the astronaut has made. She can then expand this further, encode any information into bits, and achieve FTL communication. It will be something like: we keep shooting photons at D0 and keep seeing interference pattern, until one day we go, "yep, it starts to look like a diffraction pattern now, she must have switched the panels moments ago!" Since no information can travel FTL, I'm sure my idea is flawed, but what's wrong with it? | What's wrong with this experiment showing that either FTL communication is possible or complementarity doesn't hold? The assumptions are: Alice and Bob have perfectly synchronized clocks Alice and Bob have successfully exchanged a pair of entangled photons The idea is simply to have Alice and Bob perform the Quantum Eraser Experiment (doesn't need to be the delayed choice). Alice and Bob agree on a specific time when Bob's photon will be between the "path marker" (which is usually just after the slits) and the detector. If Alice acts collpasing the wave-function on her photon, the interference pattern will disappear. If not it won't. Alice and Bob can be spatially separated... What am I misunderstanding? The only meaningful difference from this spatially separated quantum eraser experiment to one done on tabletop is that you won't be able to use a coincidence detector, but that is not impeditive to identifying the interference pattern, just will make errors more probable. Which we should be able to deal with a appropriate protocol... There is a experimental paper with a small amount of citations pointing out to the breaking of complementarity in a very similar setup: | What role does "spontaneously symmetry breaking" played in the "Higgs Mechanism"? In talking about Higgs mechanism, the first part is always some introduction to the concept of spontaneously symmetry breaking (SSB), some people saying that Higgs mechanism is the results of SSB of local gauge symmetry, some people says that we can formulate Higgs mechanism in a gauge invariant way, some people also says that we need only a non-zero vaccum expectation value... I am confused about this different or maybe same point of views. In this post: , the most highly voted answer, I still can't feel how SSB worked in Higgs mechanism. It seem that the validity of last part, the appearance of a mass term for $A$, is guaranteed if we have a non-zero equilibrium value $\phi_0$ to expand around. I do not see that the requirement that the phase of the field $\phi$ need to be fixed at some particular value to generate mass term. Thus it seems to me it is not true that SSB is really indispensable for Higgs mechanism. To put it simply: The spontanously breaking of what is attributed to Higgs mechanism? local gauge symmetry global symmetry, since breaking of a "gauge symmetry" should not have any effect on physics. In higgs mechanism, the really broken symmetry is a global one. Mathematically, it is similar in looking as fixing a gauge, but one should not think it as a spontanously breakdown of local gauge symmetry. other. Is SSB really indispensable for Higgs mechanism? yes, Higgs mechanism is relied on the SSB of some symmetry (above question), the other approches of description eventually has spontanously broke some symmetry. No, the SSB is just one way to describe Higgs mechanism (or even not a complete way), what is really need is the non-zero vaccum expectation value, for example in the linked post the requirement for the mass term to occur is to have some non-zero expectation value of $\phi$ to expand around, we do not need the phase of the field to be fixed, thus the symmetry is not broken. Other. some reference materials: States that SSB of local gauge symmetry is impossible. in the abstract states that: gauge symmetries merely reflect a redundancy in the state description and therefore the spontaneous breaking can not be an essential ingredient. Indeed, as already shown by Higgs and Kibble, the mechanism can be explained in terms of gauge invariant variables, without invoking spontaneous symmetry breaking In the introduction it says: In particular, we emphasize that global U(1) phase rotation symmetry, and not gauge symmetry, is spontaneously violated, and show that the BCS wave function is, contrary to claims in the literature, fully gauge invariant | eng_Latn | 26,991 |
Why does dust form islands on top of water? When you pour sand into water, first the dust particles that are floating on the surface, are separately all over. Then as the water flows, the dust particles should just randomly move around staying mostly separately, but for some reason, all the dust particles are moving together and sticking together into islands, just like planets are formed from dust in the solar systems. It is like there was some force that is pulling these dust particles together, and keeping them in these islands. Is this the same Van der Waals force that keeps the water molecules together? Question: Why are dust particles moving together into these islands on top of the water? | Why do Oreo crumbs float to a single glob at the very center in a glass of milk? I had Oreos and milk a while ago and left my half-full cup of milk out on the counter. Afterwards I noticed that the crumbs had surfaced in a circular coin-sized glob, and just now I looked again to see all of the crumbs seem to have compressed into a more dense glob at the very center of the cup. Why does this happen? | What happens to matter in a standard model with zero Higgs VEV? Suppose you reset the parameters of the standard model so that the Higgs field average value is zero in the vacuum, what would happen to standard matter? If the fundamental fermions go from a finite to a zero rest mass, I'm pretty sure that the electrons would fly away from nuclei at the speed of light, leaving positively charged nuclei trying to get away from each other. Looking at the solution for the Hydrogen atom, I don't see how it would be possible to have atoms with zero rest mass electrons. What happens to protons and neutrons? Since only a very small part of the mass of protons and neutrons is the rest mass of the quarks, and since they're flying around in there at relativistic speeds already, and since the nuclear force is so much stronger than the electrical force with an incredible aversion to naked color, would protons and neutrons remain bound assemblages of quarks and virtual gluons? Would they get a little larger? A little less massive? What would happen to nuclei? Would they stay together? If the protons and neutrons hold together and their properties change only some, then I might expect the same of nuclei. Different stable isotopes, different sizes, and different masses, but I would expect there would still be nuclei. Also the W and Z particles go to zero rest mass. What does that do to the electroweak interactions? Does that affect normal stable matter (outside of nuclear decay modes)? Is the weak force no longer weak? What happens to the forces overall? | eng_Latn | 26,992 |
Could the singularity of a black hole just be an iron / dark matter sphere? A singularity would break physics wouldn't it? How does a massive star collapse and suddenly fall into a point in space with no dimensions what so ever when it had a core and perfect balance between gravity and mass before its death? This would certainly make no sense in the process right. Is there a simulation where this kind of behaviour is illustrated? The only way the singularity of a black holes could make sense is when for example a massive star collapses due to gravity and its core being unable to fuse iron into a heavier element, the only thing left is pretty much the core being either iron or a new unknown element heavier than iron cough dark matter? cough . This core's gravitational force is so strong that it bends light though if we were remove the force and just look under the hood of the object, we would simply just see a spherical object made out of iron or something heavier / unknown like perhaps dark matter. TL;DR the core remains but we can't see it due to its gravitational force / strength thus a singularity would not exist. How likely is that kind of concept? (I'm definitely not an expert in this field but I want to understand this concept better and see whether my ideas could possibly make sense) | Can we have a black hole without a singularity? Assuming we have a sufficiently small and massive object such that it's escape velocity is greater than the speed of light, isn't this a black hole? It has an event horizon that light cannot escape, time freezes at this event horizon, etc. However this object is not a singularity. If a large star's mass were compressed to the size of, say, a proton, it would certainly have these properties but it would still not be a singularity as a proton does have volume. The reason "physics breaks down" at singularities is because we cannot divide by zero, but as long as the proton-sized object has volume, physics won't "break down", yet we still have an event horizon and an object that is invisible (but not undetectable) from the outside. I have read the answers to related question. I'm not sure if they don't address my specific question or if I don't understand the answers. | What role does "spontaneously symmetry breaking" played in the "Higgs Mechanism"? In talking about Higgs mechanism, the first part is always some introduction to the concept of spontaneously symmetry breaking (SSB), some people saying that Higgs mechanism is the results of SSB of local gauge symmetry, some people says that we can formulate Higgs mechanism in a gauge invariant way, some people also says that we need only a non-zero vaccum expectation value... I am confused about this different or maybe same point of views. In this post: , the most highly voted answer, I still can't feel how SSB worked in Higgs mechanism. It seem that the validity of last part, the appearance of a mass term for $A$, is guaranteed if we have a non-zero equilibrium value $\phi_0$ to expand around. I do not see that the requirement that the phase of the field $\phi$ need to be fixed at some particular value to generate mass term. Thus it seems to me it is not true that SSB is really indispensable for Higgs mechanism. To put it simply: The spontanously breaking of what is attributed to Higgs mechanism? local gauge symmetry global symmetry, since breaking of a "gauge symmetry" should not have any effect on physics. In higgs mechanism, the really broken symmetry is a global one. Mathematically, it is similar in looking as fixing a gauge, but one should not think it as a spontanously breakdown of local gauge symmetry. other. Is SSB really indispensable for Higgs mechanism? yes, Higgs mechanism is relied on the SSB of some symmetry (above question), the other approches of description eventually has spontanously broke some symmetry. No, the SSB is just one way to describe Higgs mechanism (or even not a complete way), what is really need is the non-zero vaccum expectation value, for example in the linked post the requirement for the mass term to occur is to have some non-zero expectation value of $\phi$ to expand around, we do not need the phase of the field to be fixed, thus the symmetry is not broken. Other. some reference materials: States that SSB of local gauge symmetry is impossible. in the abstract states that: gauge symmetries merely reflect a redundancy in the state description and therefore the spontaneous breaking can not be an essential ingredient. Indeed, as already shown by Higgs and Kibble, the mechanism can be explained in terms of gauge invariant variables, without invoking spontaneous symmetry breaking In the introduction it says: In particular, we emphasize that global U(1) phase rotation symmetry, and not gauge symmetry, is spontaneously violated, and show that the BCS wave function is, contrary to claims in the literature, fully gauge invariant | eng_Latn | 26,993 |
Breaking of a local symmetry is impossible, so what "discrete remnant global symmetry" is the SM-Higgs breaking? Breaking of a local symmetry is impossible. It is often said that therefore the role of the Higgs mechanism in the standard model is a different one. , Once a gauge is fixed, however, to remove the redundant degrees of freedom, the remaining (discrete!) global symmetry may undergo spontaneous symmetry-breaking exactly along the lines discussed in the previous chapter. The phrase "spontaneous breaking of local gauge symmetry" is therefore in some sense a misnomer, but a convenient one, if we think of it as a short circumlocution for "spontaneous breaking of remnant global symmetry after removal of redundant gauge degrees of freedom by appropriate gauge fixing". Or here's a similar statement from a : But is the gauge symmetry actually broken spontaneously? In the above exposition of the Higgs mechanism, there were two instances when a symmetry was broken. First, when we selected one minimum out of infinite amount of equivalent minima, a spontaneous breaking indeed took place, but only of a global symmetry. This minimum represents a vacuum, and in order to perturbatively describe the quantum field theory, we need to quantize the fields. Quantization of gauge field theories requires introduction of a gauge-fixing procedure, and during this procedure we break the gauge symmetry by hand, explicitly, not spontaneously. Thus, the two notions, EWSB and SSB, are in certain sense correct, but they do not refer to the same symmetry. [...] As Englert says in his Nobel lecture [54]: “… The vacuum is no more degenerate and strictly speaking there is no spontaneous symmetry breaking of a local symmetry. The reason why the phase with nonvanishing scalar expectation value is often labeled SSB is that one uses perturbation theory to select at zero coupling with the gauge fields a scalar field configuration from global SSB; but this preferred choice is only a convenient one. What global symmetry are they referring to? (I find it extremely strange that they don't specify the allegedly broken global symmetry.) | What role does "spontaneously symmetry breaking" played in the "Higgs Mechanism"? In talking about Higgs mechanism, the first part is always some introduction to the concept of spontaneously symmetry breaking (SSB), some people saying that Higgs mechanism is the results of SSB of local gauge symmetry, some people says that we can formulate Higgs mechanism in a gauge invariant way, some people also says that we need only a non-zero vaccum expectation value... I am confused about this different or maybe same point of views. In this post: , the most highly voted answer, I still can't feel how SSB worked in Higgs mechanism. It seem that the validity of last part, the appearance of a mass term for $A$, is guaranteed if we have a non-zero equilibrium value $\phi_0$ to expand around. I do not see that the requirement that the phase of the field $\phi$ need to be fixed at some particular value to generate mass term. Thus it seems to me it is not true that SSB is really indispensable for Higgs mechanism. To put it simply: The spontanously breaking of what is attributed to Higgs mechanism? local gauge symmetry global symmetry, since breaking of a "gauge symmetry" should not have any effect on physics. In higgs mechanism, the really broken symmetry is a global one. Mathematically, it is similar in looking as fixing a gauge, but one should not think it as a spontanously breakdown of local gauge symmetry. other. Is SSB really indispensable for Higgs mechanism? yes, Higgs mechanism is relied on the SSB of some symmetry (above question), the other approches of description eventually has spontanously broke some symmetry. No, the SSB is just one way to describe Higgs mechanism (or even not a complete way), what is really need is the non-zero vaccum expectation value, for example in the linked post the requirement for the mass term to occur is to have some non-zero expectation value of $\phi$ to expand around, we do not need the phase of the field to be fixed, thus the symmetry is not broken. Other. some reference materials: States that SSB of local gauge symmetry is impossible. in the abstract states that: gauge symmetries merely reflect a redundancy in the state description and therefore the spontaneous breaking can not be an essential ingredient. Indeed, as already shown by Higgs and Kibble, the mechanism can be explained in terms of gauge invariant variables, without invoking spontaneous symmetry breaking In the introduction it says: In particular, we emphasize that global U(1) phase rotation symmetry, and not gauge symmetry, is spontaneously violated, and show that the BCS wave function is, contrary to claims in the literature, fully gauge invariant | What is the relation between the Higgs field and chirality? Wikipedia that the spontaneous breaking of chiral symmetry "is responsible for the bulk of the mass (over 99%) of the nucleons". How do the nucleons gain mass from the spontaneous breaking of chiral symmetry? Why don't leptons gains mass from it? What is the role of the Higgs field in this all? | eng_Latn | 26,994 |
Electroweak symmetry breaking and mass generation Can someone please describe how the mass of the fermions is generated by the Higgs relative to electroweak symmetry breaking? Or other way around: Why does a breaking of the electroweak symmetry generate a fermion mass? Hence, what's the difference to chiral symmetry breaking which causes, e.g., the pion masses? I found it on and there is maybe an another question related to: That are probably very plain questions aiming at a general understanding/access. I'm trying to separate the involving terms and mechanisms from each other.. | What is the relation between the Higgs field and chirality? Wikipedia that the spontaneous breaking of chiral symmetry "is responsible for the bulk of the mass (over 99%) of the nucleons". How do the nucleons gain mass from the spontaneous breaking of chiral symmetry? Why don't leptons gains mass from it? What is the role of the Higgs field in this all? | Why do prisms work (why is refraction frequency dependent)? It is well known that a can "split light" by separating different frequencies of light: Many sources state that the reason this happens is that the is different for different frequencies. This is known as . My question is about why dispersion exists. Is frequency dependence for refraction a property fundamental to all waves? Is the effect the result of some sort of non-linearity in response by the refracting material to electromagnetic fields? Are there (theoretically) any materials that have an essentially constant, non-unity index of refraction (at least for the visible spectrum)? | eng_Latn | 26,995 |
Recommendation: Advanced topics in quantum field theory I have read Srednicki's Quantum Field Theory book. I want to learn more about advanced topics in field theory, such as geometry and topology in field theory, topology defect, anomaly, soliton, instanton, renormalization，advanced application in condensed matter physics and so on. Does anyone have anything recommended? Thanks | What is a complete book for introductory quantum field theory? There's a fairly standard two or three-semester curriculum for introductory quantum field theory, which covers topics such as: classical field theory background canonical quantization, path integrals the Dirac field quantum electrodynamics computing $S$-matrix elements in perturbation theory, decay rates, cross sections renormalization at one loop Yang-Mills theory spontaneous symmetry breaking the Standard Model What is a good, complete and comprehensive book that covers topics such as these? | What's the deepest reason why QCD bound states have integer charge? What's the deepest reason why QCD bound states have integer electric charge, i.e. equal to an integer times the electron charge? Given that the quarks have the fractional electric charges they do, this is a consequence of color confinement. The charges of the quarks are constrained in the context of the standard model by anomaly cancellation, and can be explained by grand unification. The GUT explanation for the charges doesn't care about the bound state spectrum of the QCD sector, so it just seems to be a coincidence that hadrons (which are composite) have integer charge, and that leptons (which are elementary) also have integer charge. Now maybe there's some anthropic argument for why such a coincidence is useful (in the case of proton and electron, it gives us atoms as we know them). Or maybe you can argue that GUTs naturally produce fractionally charged particles and strongly coupled sectors, and it's just not much of a coincidence. But I remain curious as to whether Seiberg duality, anyons, some UV/IR relationship... could really produce something like the lepton-hadron charge coincidence, for deeper reasons. I suppose one is looking for a theory in which properties of bound states in one sector have a direct and nontrivial relationship to properties of elementary states in another sector. Is there anything like this out there? (This question was prompted by muster-mark's many recent questions about fractional charge, and by a that the hadron-lepton charge coincidence is a "semi-coincidence", which assured me that I wasn't overlooking some obvious explanation.) | eng_Latn | 26,996 |
Has the formation of a new quark pair as we separate two quarks been observed or is it only a prediction? Because of quark confinement we know that as we try to separate quarks appart the energy required will increase, but if the force is strong enough (I do not know if possible in the lab, but at least could happen near a blackhole horizon if one the quarks enters the black hole) part of that energy is used to form a new quark pair so that the two original ones will still be confined. My question is has this been observed experimentally or is it only a prediction of the standard (or some other) model? | Has confinement been experimentally observed? So, confinement has obviously been shown by lattice gauge theory to be a predicted aspect of QCD. However, to what extent has it been observed in experimental physics? | Why we use $L_2$ Space In QM? I asked this question for many people/professors without getting a sufficient answer, why in QM Lebesgue spaces of second degree are assumed to be the one that corresponds to the Hilbert vector space of state functions, from where this arises? and why 2-order space that assumes the following inner product: $\langle\phi|\psi\rangle =\int\phi^{*}\psi\,dx$ While there is many ways to define the inner product. In Physics books, this always assumed as given, never explains it, also I tried to read some abstract math books on this things, and found some concepts like "Metric weight" that will be minimized in such spaces, even so I don't really understand what is behind that, so why $L_2$? what special about them? Who and how physicists understood that those are the one we need to use? | eng_Latn | 26,997 |
Is there a $t$-channel process for $q\bar{q} \rightarrow gg$? Let's consider the process $q\bar{q}\rightarrow gg$. Is the following Feynman diagram allowed: I ask because of the following reason: At the upper vertex, the $q$ emits a gluon $g$ and the propagator would then be a $q$, I guess, but at the lower vertex, the propagator would then emit a gluon $g$ and turn into a $\bar{q}$. Would this not be a violation of electric charge at the lower vertex, because the gluon $g$ does not have any charge? | What is the Mediator in this Feynman Diagram $q\bar{q} \rightarrow gg$? Let's consider the t-channel version of the process $q\bar{q} \rightarrow gg$. What is the mediator in this case, a $q$ or a $\bar{q}$? Naively, I would have thought a $q$ (as to have one fermion line), but I am not $100 \%$ sure. | Can a quasiclassical electron wave packet in elliptic orbit be formed from bound hydrogen-like eigenstates? Position probability densities of eigenstates of hydrogen-like systems have axial symmetry, so that the wavefunction too much resembles the circular orbits in Bohr's model. I'd like to have a demonstration of correspondence principle, where an electron would be localized to look somewhat like a classical particle, and move in an elliptic (non-circular) orbit around a nucleus. It seems though that if we try to make a wave packet too localized, then it'll disintegrate (get scattered by the nucleus) too fast to see anything resembling an elliptic orbit. OTOH, if we take it too spread out, it'll have to be quite far from the nucleus so as to avoid hitting it, and thus it'll have high total energy, which may appear to be above ionization threshold (at least partially), after which it'd be quite hard to analytically calculate evolution of the wave packet. Thus my question is: is it possible to form a more or less localized wave packet, which would (on average) move in an obviously-elliptic orbit (major/minor axes ratio of 4:3 or higher), and only require bound states to fully represent it? If yes, then what properties (FWHM, apocenter, angular momentum etc.) should it have for this to be possible? | eng_Latn | 26,998 |
Why are $W$ bosons massless above electroweak scale? Because of the Higgs mechanism, one must replace the Higgs field $\phi$ with $\phi_0 + \phi_1$ where $\phi_0$ is the vacuum expectation value. As far as I understand, the $\phi_0$ gives the mass term to bosons after developping the product $D_{\mu}\phi D^\mu \phi$. But I don't understand why these mass terms should disappear above the electroweak scale where it is said that the gauge bosons are massless. | Are there massless bosons at scales above electroweak scale? Spontaneous electroweak symmetry breaking (i.e. $SU(2)\times U(1)\to U(1)_{em}$ ) is at scale about 100 Gev. So, for , gauge bosons $Z$ & $W$ have masses about 100 GeV. But before this spontaneous symmetry breaking ( i.e. Energy > 100 GeV) the symmetry $SU(2)\times U(1)$ is not broken, and therefore gauge bosons are massless. The same thing happens when we go around energy about $10^{16}$ GeV, where we have the Grand Unification between electroweak and strong interactions, in some bigger group ($SU(5)$, $SO(10)$ or others). So theoretically we should find gauge bosons $X$ and $Y$ with masses about $10^{16}$ GeV after GUT symmetry breaks into the Standard Model gauge group $SU(3)\times SU(2)\times U(1)$, and we should find massless X and Y bosons at bigger energies (where GUT isn't broken). So this is what happened in the early universe: when temperature decreased, spontaneous symmetry breaking happened and firstly $X$ & $Y$ gauge bosons obtained mass and finally $Z$ & $W$ bosons obtained mass. Now, I ask: have I understood this correctly? In other words, if we make experiments at energy above the electroweak scale (100 GeV) we are where $SU(2)\times U(1)$ isn't broken and then we should (experimentally) find $SU(2)$ and $U(1)$ massless gauge bosons, i.e. $W^1$, $W^2$, $W^3$ and $B$ with zero mass? But this is strange, because if I remember well in LHC we have just make experiments at energy about 1 TeV, but we haven't discovered any massless gauge bosons. | "Reality" of EM waves vs. wavefunction of individual photons - why not treat the wave function as equally "Real"? In thinking how to ask this question (somewhat) succinctly, I keep coming back to a Microwave Oven. A Microwave Oven has a grid of holes over the window specifically designed to be smaller in diameter than the wavelength of the microwaves it produces, yet larger than the wavelengths of the visible light spectrum - this is so you can watch your food being heated without getting an eye full of microwaves. The "realness" of electromagnetic waves seems indisputable - both from the microwave example above, and also because if I want to broadcast a radio wave with a certain wavelength, then I need to make sure I have an antenna of corresponding length to produce the wave I'm looking for. Furthermore, we discuss and treat these waves as real, measurable "objects" that exist and can be manipulated. Now, if I want to describe the behavior of my Microwave Oven in the framework of QM (let's pretend my oven is going to only produce 1 photon of energy corresponding to a wavelength of the microwave spectrum for simplicity) then I'll describe the behavior of that photon as a wavefunction that evolves over time and gives a probability distribution within my microwave that similarly does not allow the photon to pass through the safety grid and exit the oven cavity giving me a retinal burn. The difference is, the wavefunction is never treated as something "real" in this description. When the safety grid is described as working to protect you because it has holes smaller than the wavelength of the classical waves it's blocking, this is a useful description that seems to describe "real" objects/be-ables. While it is possible to describe why an individual photon has low probability of passing through the same grid but extended physical properties such as wavelength (in space) are treated as non-real because we're dealing with a point particle and with behavior described by something we also treat as non-real (the wavefunction); it seems unclear to me why we insist this wave function which predicts behavior of physical measurements so well is somehow "non-real." Put another way, if we have no problem treating EM waves as "Real," then why do we insist on treating the wavefunction that describes the same behavior as "unreal?" I understand there is recent research (Eric Cavalcanti and his group for one) trying to argue this point, but as every respectable physics professor, I've ever encountered, has treated the wavefunction as an indisputably non-real mathematical tool, I needed to ask this community for an answer. | eng_Latn | 26,999 |
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