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0911.3375
|
Transverse and Longitudinal Doppler Effects of the Sunbeam Spectra and Earth-Self Rotation and Orbital Velocities, the Mass of the Sun and Others
|
The transverse and longitudinal Doppler effects of the sunbeam spectra are shown to result in the earth parameters such as the earth-self rotation and revolution velocities, the earth orbit semi-major axis, the earth orbital angular momentum, the earth axial tilt, the earth orbit eccentricity, the local latitude and the mass of the sun. The sunbeam global positioning scheme is realized, including the earth orbital position. PACS numbers: 91.10.Fc, 95.10.Km, 91.10.Da, 91.10.Jf.
|
[
"Physics Archive->physics->physics.gen-ph"
] | 2009-11-17T19:09:26Z |
1605.07276
|
Approximate particle number distribution from direct stochastic sampling of the Wigner function
|
We consider the Wigner quasi-probability distribution function of a single mode of an electromagnetic or matter-wave field to address the question of whether a direct stochastic sampling and binning of the absolute square of the complex field amplitude can yield a distribution function $\tilde{P}_n$ that closely approximates the true particle number probability distribution $P_n$ of the underlying quantum state. By providing an operational definition of the binned distribution $\tilde{P}_n$ in terms of the Wigner function, we explicitly calculate the overlap between $\tilde{P}_n$ and ${P}_n$ and hence quantify the statistical distance between the two distributions. We find that there is indeed a close quantitative correspondence between $\tilde{P}_n$ and $P_n$ for a wide range of quantum states that have smooth and broad Wigner function relative to the scale of oscillations of the Wigner function for the relevant Fock state. However, we also find counterexamples, including states with high mode occupation, for which $\tilde{P}_n$ does not closely approximate $P_n$.
|
[
"Physics Archive->quant-ph"
] | 2016-05-24T03:07:10Z |
hep-ph/0208194
|
Isospin violation in e+ e- --> B Bbar
|
The ratio of the B+ B- and B0 B0bar production rates in e+ e- annihilation is computed as a function of the B meson velocity and BB* pi coupling constant, using a non-relativistic effective field theory.
|
[
"Physics Archive->hep->hep-ph"
] | 2002-08-21T20:01:50Z |
hep-ph/0510371
|
Gluon shadowing and unitarity effects
|
New data from HERA experiment on deep inelastic scattering have been used to parametrize nucleon and Pomeron structure functions. Within the Gribov theory, the parameterizations were employed to calculate gluon shadowing for various heavy ions. The latter was compared with predictions from other models. Calculations of multiplicity reduction due to gluon shadowing for d+Au collisions at forward rapidities at $\sqrt{s}$=200 GeV are in good agreement with BRAHMS data on the nuclear modification factor.
|
[
"Physics Archive->hep->hep-ph"
] | 2005-10-28T12:01:24Z |
1911.08844
|
On the physics of transient ejection from bubble bursting
|
The transient ejection due to a bubble bursting at the interface of a liquid with a gas environment is here described using a dynamical scaling analysis along the process. We show here that the ejection of a liquid microjet requires the backfire of a vortex ring inside the liquid to preserve physical symmetry, which involves a non-trivial scaling. We present the first single uniformly valid expression for the size and speed of ejected droplets for the whole range of the Ohnesorge and Bond numbers where droplet ejection occurs. The evolution of the flow variables, the apparent singularity for a critical Ohnesorge number, and the dispersion of data around this point are explained. Our model generalizes or displaces other recently proposed ones, impacting for instance the statistical description of sea spray.
|
[
"Physics Archive->physics->physics.flu-dyn"
] | 2019-11-20T11:55:44Z |
2304.07595
|
The Gravito-Maxwell Equations of General Relativity in the local reference frame of a GR-noninertial observer
|
We show that the acceleration-difference of neighboring free-falling particles (= geodesic deviation) measured in the local reference frame of a GR-noninertial observer is not given by the Riemann tensor. With the gravito-electric field of GR defined as the acceleration of free-falling quasistatic particles relative to the observer, the divergence of the gravito-electric field measured in the reference frame of a GR-noninertial observer is different from the Ricci curvature $R^0_{\,\,0}$. We derive our exact, explicit, and simple gravito-Gauss law for the divergence of the gravito-electric field in our new reference frame of a GR-noninertial observer with his LONB (Local Ortho-Normal Basis) and his LONB-connections in his time and 3-directions: the sources of the divergence of the gravito-electric field are contributed by all fields including the GR-gravitational fields, gravito-electric and gravito-magnetic. In the reference frame of a GR-inertial observer our gravito-Gauss law coincides with Einstein's $R^0_{\,\,0}$ equation, which does not have gravitational fields as sources. We derive the gravito-Ampere law, the gravito-Faraday law and the law for the divergence of the gravito-magnetic field. The densities of energy, momentum, and momentum-flow of GR-gravitational fields are local observables, but depend on observer with his local reference frame: these quantities are zero if measured by a GR-inertial observer. For a GR-noninertial observer the sources of gravitational energy, momentum, and momentum-flow densities have the opposite sign from the electromagnetic and matter sources. In the gravito-Gauss law the sources contributed by gravitational energy and momentum-flow densities have a repulsive effect on the gravitational acceleration-difference of particles.
|
[
"Physics Archive->gr-qc"
] | 2023-04-15T17:03:16Z |
2103.12249
|
Magnetic field-driven transition between valence bond solid and antiferromagnetic order in distorted triangular lattice
|
A molecular Mott insulator $\kappa$-(ET)$_2$B(CN)$_4$ [ET = bis(ethylenedithio)tetrathiafulvalene] with a distorted triangular lattice exhibits a quantum disordered state with gapped spin excitation in the ground state. $^{13}$C nuclear magnetic resonance, magnetization, and magnetic torque measurements reveal that magnetic field suppresses valence bond order and induces long-range magnetic order above a critical field $\sim 8$ T. The nuclear spin-lattice relaxation rate $1/T_1$ shows persistent evolution of antiferromagnetic correlation above the transition temperature, highlighting a quantum spin liquid state with fractional excitations. The field-induced transition as observed in the spin-Peierls phase suggests that the valence bond order transition is driven through renormalized one-dimensionality and spin-lattice coupling.
|
[
"Physics Archive->cond-mat->cond-mat.str-el"
] | 2021-03-23T00:54:18Z |
1404.3214
|
Bounds on quantum communication via Newtonian gravity
|
Newtonian gravity yields specific observable consequences, the most striking of which is the emergence of a $1/r^2$ force. In so far as communication can arise via such interactions between distant particles, we can ask what would be expected for a theory of gravity that only allows classical communication. Many heuristic suggestions for gravity-induced decoherence have this restriction implicitly or explicitly in their construction. Here we show that communication via a $1/r^2$ force has a minimum noise induced in the system when the communication cannot convey quantum information, in a continuous time analogue to Bell's inequalities. Our derived noise bounds provide tight constraints from current experimental results on any theory of gravity that does not allow quantum communication.
|
[
"Physics Archive->quant-ph"
] | 2014-04-11T20:01:08Z |
1412.4252
|
X-ray coherent pulsations during a sub-luminous accretion disk state of the transitional millisecond pulsar XSS J12270-4859
|
We present the first detection of X-ray coherent pulsations from the transitional millisecond pulsar XSS J12270-4859, while it was in a sub-luminous accretion disk state characterized by a 0.5-10 keV luminosity of 5E33 erg/s (assuming a distance of 1.4 kpc). Pulsations were observed by XMM-Newton at an rms amplitude of (7.7 +/- 0.5)% with a second harmonic stronger than the the fundamental frequency, and were detected when the source is neither flaring nor dipping. The most likely interpretation of this detection is that matter from the accretion disk was channelled by the neutron star magnetosphere and accreted onto its polar caps. According to standard disk accretion theory, for pulsations to be observed the mass in-flow rate in the disk was likely larger than the amount of plasma actually reaching the neutron star surface; an outflow launched by the fast rotating magnetosphere then probably took place, in agreement with the observed broad-band spectral energy distribution. We also report about the non-detection of X-ray pulsations during a recent observation performed while the source behaved as a rotationally-powered radio pulsar.
|
[
"Physics Archive->astro-ph->astro-ph.HE"
] | 2014-12-13T16:29:15Z |
1810.10748
|
Towards Delay-Tolerant Flexible Data Access Control for Smart Grid with Renewable Energy Resources
|
In the Smart Grid with Renewable Energy Resources (RERs), the Residential Units (RUs) with Distributed Energy Resources (DERs) are considered to be both power consumers and suppliers. Specifically, RUs with excessive renewable generations can trade with the utility in deficit of power supplies for mutual benefits. It causes two challenging issues. First, the trading data of RUs is quite sensitive, which should be only accessed by authorized users with fine-grained policies. Second, the behaviors of the RUs to generate trading data are spontaneous and unpredictable, then the problem is how to guarantee system efficiency and delay tolerance simultaneously. In this paper, we propose a delay-tolerant flexible data access control scheme based on Key Policy Attribute Based Encryption (KP-ABE) for Smart Grid with Renewable Energy Resources (RERs). We adopt the secret sharing scheme (SSS) to realize a flexible access control with encryption delay tolerance. Furthermore, there is no central trusted server to perform the encryption/decryption. We reduce the computation cost on RUs and operators via a semi-trusted model. The analysis shows that the proposed scheme can meet the data security requirement of the Smart Grid with RERs, and it also has less cost compared with other popular models.
|
[
"Computer Science Archive->cs.CR"
] | 2018-10-25T07:35:59Z |
1307.7238
|
Analysis and Modeling of Network Connectivity in Routing Protocols for MANETs and VANETs
|
In this paper, a framework is presented for node distribution with respect to density, network connectivity and communication time. According to modeled framework we evaluate and compare the performance of three routing protocols; Ad-hoc On-demand Distance Vector (AODV), Dynamic Source Routing (DSR) and Fisheye State Routing (FSR) in MANETs and VANETs using two Mac-layer protocols; 802.11 and 802.11p. We have further modified these protocols by changing their routing information exchange intervals; MOD AODV, MOD DSR and MOD FSR. A comprehensive simulation work is performed in NS-2 for the comparison of these routing protocols for varying mobilities and scalabilities of nodes. To evaluate their efficiency; throughput, End-to-End Delay (E2ED) and Normalized Routing Load (NRL) of these protocols are taken into account as performance parameters. After extensive simulations, we observe that AODV outperforms both with MANETs and VANETs.
|
[
"Computer Science Archive->cs.NI"
] | 2013-07-27T09:21:57Z |
gr-qc/0502081
|
Gravitational collapse in asymptotically Anti-de Sitter/de Sitter backgrounds
|
We study here the gravitational collapse of a matter cloud with a non-vanishing tangential pressure in the presence of a non-zero cosmological term. Conditions for bounce and singularity formation are derived for the model. It is also shown that when the tangential pressures vanish, the bounce and singularity conditions reduce to that of the dust case studied earlier. The collapsing interior is matched with an exterior which is asymptotically de Sitter or anti de Sitter, depending on the sign of cosmological constant. The junction conditions for matching the cloud to exterior are specified. The effect of the cosmological term on apparent horizons is studied in some detail, and the nature of central singularity is analyzed. We also discuss here the visibility of the singularity and implications for the cosmic censorship conjecture.
|
[
"Physics Archive->gr-qc",
"Physics Archive->hep->hep-th"
] | 2005-02-19T15:53:23Z |
1101.1173
|
On an imaginary exponential functional of Brownian motion
|
We investigate a random integral which provides a natural example of an imaginary exponential functional of Brownian motion. This functional shows up in the study of the binary annihilation process, within the Doi-Peliti formalism for reaction-diffusion systems. The main emphasis is put on the complementarity between the usual Langevin approach and another approach based on the similarity with Kesten variables and other one-dimensional disordered systems. Even though neither of these routes leads to the full solution of the problem, we have obtained a collection of results describing various regimes of interest.
|
[
"Mathematics Archive->math.MP",
"Physics Archive->cond-mat->cond-mat.stat-mech",
"Physics Archive->math-ph"
] | 2011-01-06T09:21:46Z |
1903.09700
|
Modified exchange interaction between magnetic impurities in spin-orbit coupled quantum wires
|
Indirect exchange interaction between magnetic impurities in one dimensional systems is a matter of long discussions since Kittel has established that in the asymptotic limit it decays as the inverse of distance x between the impurities. In this work we investigate this problem in a quantum wire with Rashba spin-orbit coupling (SOC). By employing a second order perturbation theory we find that one additional oscillatory term appears in each of the RKKY, the Dzaloshinkii-Moryia and the Ising couplings. Remarkably, these extra terms resulting from the spin precession of the conduction electrons induced by the SOC do not decay as in the usual RKKY interaction. We show that these extra oscillations arise from the finite momenta band splitting induced by the spin-orbit coupling that modifies the spin-flip scatterings occurring at the Fermi energy. Our findings open up a new perspective in the long-distance magnetic interactions in solid state systems.
|
[
"Physics Archive->cond-mat->cond-mat.mes-hall"
] | 2019-03-22T20:27:40Z |
1010.4753
|
Relative outer automorphisms of free groups
|
Let $A_1,...,A_k$ be a system of free factors of $F_n$. The group of relative automorphisms $Aut(F_n;A_1,...,A_k)$ is the group given by the automorphisms of $F_n$ that restricted to each $A_i$ are conjugations by elements in $F_n$. The group of relative outer automorphisms is defined as $Out(F_n;A_1,...,A_k) = Aut(F_n;A_1,...,A_k)/Inn(F_n)$, where $Inn(F_n)$ is the normal subgroup of $Aut(F_n)$ given by all the inner automorphisms. We define a contractible space on which $Out(F_n;A_1,...,A_k)$ acts with finite stabilizers and we compute the virtual cohomological dimension of this group.
|
[
"Mathematics Archive->math.GR",
"Mathematics Archive->math.GT"
] | 2010-10-22T16:39:23Z |
1408.2731
|
More chips off of Asteroid (4) Vesta: characterization of eight Vestoids and their HED meteorite analogs
|
This work reports high quality NIR spectra, and their respective interpretations, for eight Vp type asteroids, as defined by Carvano et al. (2010), that were observed at the NASA Infrared Telescope Facility on January 14, 2013 UT. They include (3867) Shiretoko, (5235) Jean-Loup, (5560) Amytis, (6331) 1992 FZ1, (6976) Kanatsu, (17469) 1991 BT, (29796) 1999 CW77, and (30872) 1992 EM17. All eight asteroids exhibit the broad 0.9 and 1.9 micron mineral absorption features indicative of pyroxene on each asteroid's surface. Data reduction and analysis via multiple techniques produced consistent results for the derived spectral absorption band centers and average pyroxene surface chemistries for all eight asteroids (Reddy et al., 2012; Lindsay et al., 2013,2014; Gaffey et al., 2002; Burbine et al., 2009). (3867) Shiretoko is most consistent with the eucrite meteorites while the remaining seven asteroids are most consistent with the howardite meteorites. The existing evidence suggests that all eight of these Vp type asteroids are genetic Vestoids that probably originated from Vesta's surface.
|
[
"Physics Archive->astro-ph->astro-ph.EP"
] | 2014-08-12T15:00:17Z |
1109.0683
|
Development of the Schrodinger equation for attosecond laser pulse interaction with Planck gas
|
The creation of the new particles by the interaction of the ultrarelativistic ions,from Large Hadron Collider(LHC), and attosecond laser pulse open new possibilities for laser physicists community .In this paper we propose the hyperbolic Schr\"odinger equation (HSE) for gas of the "classical" particles "i.e. particles with mass= Planck mass We discuss the inclusion of the gravity to the HSE The solution of the HSE for a particle in a box is obtained. It is shown that for particles with m greater than Mp the energy spectrum is independent of the mass of particle. Key words: attosecond laser pulses, Schrodinger equation, Planck particles, thermal processes
|
[
"Physics Archive->physics->physics.gen-ph"
] | 2011-09-04T07:49:47Z |
1506.05919
|
Norm computation and analytic continuation of vector valued holomorphic discrete series representations
|
In this paper we compute explicitly the norm of the vector-valued holomorphic discrete series representations, when its $K$-type is "almost multiplicity-free." As an application, we discuss the properties of highest weight modules, such as unitarizability, reducibility and composition series.
|
[
"Mathematics Archive->math.RT"
] | 2015-06-19T09:01:43Z |
2302.14296
|
Discrete-time Optimal Covariance Steering via Semidefinite Programming
|
This paper addresses the optimal covariance steering problem for stochastic discrete-time linear systems subject to probabilistic state and control constraints. A method is presented for efficiently attaining the exact solution of the problem based on a lossless convex relaxation of the original non-linear program using semidefinite programming. Both the constrained and the unconstrained versions of the problem with either equality or inequality terminal covariance boundary conditions are addressed. We first prove that the proposed relaxation is lossless for all of the above cases. A numerical example is then provided to illustrate the method. Finally, a comparative study is performed in systems of various sizes and steering horizons to illustrate the advantages of the proposed method in terms of computational resources compared to the state of the art.
|
[
"Computer Science Archive->cs.SY",
"Electrical Engineering and Systems Science Archive->eess.SY"
] | 2023-02-28T04:04:36Z |
1312.7775
|
Representing analytic cohomology groups of complex manifolds
|
Consider a holomorphic vector bundle $L\to X$ and an open cover ${\frak U}=\{U_a\colon a\in A\}$ of $X$, parametrized by a complex manifold $A$. We prove that the sheaf cohomology groups $H^q(X,L)$ can be computed from the complex $C^{\bullet}_{\text{hol}}$ $({\frak U},L)$ of cochains $(f_{a_0\ldots a_q})_{a_0,\ldots, a_q\in A}$ that depend holomorphically on the $a_j$, provided $S=\{(a,x)\in A\times X\colon x\in U_a\}$ is a Stein open subset of $A\times X$. The result is proved in the setting of Banach manifolds, and is applied to study representations on cohomology groups induced by a holomorphic action of a complex reductive Lie group on $L$.
|
[
"Mathematics Archive->math.AG",
"Mathematics Archive->math.CV"
] | 2013-12-30T16:48:16Z |
1906.01638
|
KiDS-SQuaD II: Machine learning selection of bright extragalactic objects to search for new gravitationally lensed quasars
|
The KiDS Strongly lensed QUAsar Detection project (KiDS-SQuaD) aims at finding as many previously undiscovered gravitational lensed quasars as possible in the Kilo Degree Survey. This is the second paper of this series where we present a new, automatic object classification method based on machine learning technique. The main goal of this paper is to build a catalogue of bright extragalactic objects (galaxies and quasars), from the KiDS Data Release 4, with a minimum stellar contamination, preserving the completeness as much as possible, to then apply morphological methods to select reliable gravitationally lensed (GL) quasar candidates. After testing some of the most used machine learning algorithms, decision trees based classifiers, we decided to use CatBoost, that was specifically trained with the aim of creating a sample of extragalactic sources as clean as possible from stars. We discuss the input data, define the training sample for the classifier, give quantitative estimates of its performances, and finally describe the validation results with Gaia DR2, AllWISE, and GAMA catalogues. We have built and make available to the scientific community the KiDS Bright EXtraGalactic Objects catalogue (KiDS-BEXGO), specifically created to find gravitational lenses. This is made of $\approx6$ millions of sources classified as quasars ($\approx 200\,000$) and galaxies ($\approx 5.7$M), up to $r<22^m$. From this catalog we selected 'Multiplets': close pairs of quasars or galaxies surrounded by at least one quasar, presenting the 12 most reliable gravitationally lensed quasar candidates, to demonstrate the potential of the catalogue, which will be further explored in a forthcoming paper. We compared our search to the previous one, presented in the first paper from this series, showing that employing a machine learning method decreases the stars-contaminators within the GL candidates.
|
[
"Physics Archive->astro-ph->astro-ph.GA",
"Physics Archive->astro-ph->astro-ph.IM"
] | 2019-06-04T16:26:26Z |
1206.5644
|
General Static (Intersecting) Brane Solutions
|
We present one extra parameter worth of new static brane and intersecting brane solutions in string/M theory. These general solutions may be obtained by solving the equations of motion directly. But, in this letter, we first obtain the general eleven dimensional vacuum solutions, and then generate the brane solutions by U duality operations -- namely boosting, dimensional reduction and uplifting, and S and T dualties. Such general solutions will be needed in the study of higher dimensional brane stars and their collapse.
|
[
"Physics Archive->gr-qc",
"Physics Archive->hep->hep-th"
] | 2012-06-25T11:03:22Z |
2005.08971
|
Simba: The average properties of the circumgalactic medium of $2 \leq z \leq 3$ quasars are determined primarily by stellar feedback
|
We use the Simba cosmological hydrodynamic simulation suite to explore the impact of feedback on the circumgalactic medium (CGM) and intergalactic medium (IGM) around $2 \leq z \leq 3$ quasars. We identify quasars in Simba as the most rapidly-accreting black holes, and show that they are well-matched in bolometric luminosity and correlation strength to real quasars. We extract Lyman-alpha (Ly-a) absorption in spectra passing at different transverse distances (10 kpc $\lesssim b \lesssim$ 10 Mpc) around those quasars, and compare to observations of the mean Ly-a absorption profile. The observations are well reproduced, except within 100 kpc from the foreground quasar, where Simba overproduces absorption; this could potentially be mitigated by including ionisation from the quasar itself. By comparing runs with different feedback modules activated, we find that (mechanical) AGN feedback has little impact on the surrounding CGM even around these most highly luminous black holes, while stellar feedback has a significant impact. By further investigating thermodynamic and kinematic properties of CGM gas, we find that stellar feedback, and not AGN feedback, is the primary physical driver in determining the average properties of the CGM around $z\sim 2-3$ quasars. We also compare our results with previous works, and find that Simba predicts much more absorption within 100 kpc than the Nyx and Illustris simulations, showing that the Ly-a absorption profile can be a powerful constraint on simulations. Instruments such as VLT-MUSE and upcoming surveys (e.g., WEAVE and DESI) promise to further improve such constraints.
|
[
"Physics Archive->astro-ph->astro-ph.CO",
"Physics Archive->astro-ph->astro-ph.GA"
] | 2020-05-18T18:00:00Z |
2106.00983
|
Nuclear reaction measurements of 80.5 MeV/u 12C beam bombarding on C, W, Cu, Au, Pb targets
|
To get the energy spectrum distribution and cross-sections of emitted light charged particles and explore the nuclear reaction, a experiment of 80.5 MeV/u 12C beam bombarding on C, W, Cu, Au, Pb targets has been carried out at Institute of Modern Physics, Chinese Academy of Science. 30, 60 and 120 degree relative to the incident beam have been detected using three sets of telescope detectors. The results indicate that there is a tendency that heavier targets have larger double differential cross-sections and the emitted fragments are more likely to go forward. Besides, the decrease of cross-sections of fragments producing with the increasing emitted angles may follow some kind of pattern.
|
[
"Physics Archive->nucl->nucl-ex"
] | 2021-06-02T07:03:38Z |
1605.01136
|
Atomically Thin Boron Nitride: Unique Properties and Applications
|
Atomically thin boron nitride (BN) is an important two-dimensional (2D) nanomaterial, with many properties distinct from graphene. In this feature article, these unique properties and associated applications often not possible from graphene are outlined. The article starts with characterization and identification of atomically thin BN. It is followed by demonstrating their strong oxidation resistance at high temperatures and applications in protecting metals from oxidation and corrosion. As flat insulators, BN nanosheets are ideal dielectric substrates for surface enhanced Raman spectroscopy (SERS) and electronic devices based on 2D heterostructures. The light emission of BN nanosheets in the deep ultraviolet (DUV) and ultraviolet (UV) regions are also included for its scientific and technological importance. The last part is dedicated to synthesis, characterization, and optical properties of BN nanoribbons, a special form of nanosheets.
|
[
"Physics Archive->cond-mat->cond-mat.mtrl-sci"
] | 2016-05-04T04:15:23Z |
2102.13116
|
The radial acceleration relation in a $\Lambda$CDM universe
|
We study the radial acceleration relation (RAR) between the total ($a_{\rm tot}$) and baryonic ($a_{\rm bary}$) centripetal acceleration profiles of central galaxies in the cold dark matter (CDM) paradigm. We analytically show that the RAR is intimately connected with the physics of the quasi-adiabatic relaxation of dark matter in the presence of baryons in deep potential wells. This cleanly demonstrates how the mean RAR and its scatter emerge in the low-acceleration regime ($10^{-12}\,{\rm m\,s}^{-2}\lesssim a_{\rm bary}\lesssim10^{-10}\,{\rm m\,s}^{-2}$) from an interplay between baryonic feedback processes and the distribution of CDM in dark halos. Our framework allows us to go further and study both higher and lower accelerations in detail, using analytical approximations and a realistic mock catalog of $\sim342,000$ low-redshift central galaxies with $M_r\leq-19$. We show that, while the RAR in the baryon-dominated, high-acceleration regime ($a_{\rm bary}\gtrsim10^{-10}\,{\rm m\,s}^{-2}$) is very sensitive to details of the relaxation physics, a simple `baryonification' prescription matching the relaxation results of hydrodynamical CDM simulations is remarkably successful in reproducing the observed RAR without any tuning. And in the (currently unobserved) ultra-low-acceleration regime ($a_{\rm bary}\lesssim 10^{-12}\,{\rm m\,s}^{-2}$), the RAR is sensitive to the abundance of diffuse gas in the halo outskirts, with our default model predicting a distinctive break from a simple power-law-like relation for HI-deficient, diffuse gas-rich centrals. Our mocks also show that the RAR provides more robust, testable predictions of the $\Lambda$CDM paradigm at galactic scales, with implications for alternative gravity theories, than the baryonic Tully-Fisher relation.
|
[
"Physics Archive->astro-ph->astro-ph.CO",
"Physics Archive->astro-ph->astro-ph.GA"
] | 2021-02-25T19:00:02Z |
1901.04472
|
EvoMaster: Evolutionary Multi-context Automated System Test Generation
|
This paper presents EvoMaster, an open-source tool that is able to automatically generate system level test cases using evolutionary algorithms. Currently, EvoMaster targets RESTful web services running on JVM technology, and has been used to find several faults in existing open-source projects. We discuss some of the architectural decisions made for its implementation, and future work.
|
[
"Computer Science Archive->cs.SE"
] | 2019-01-12T14:10:13Z |
2106.02493
|
Homological Time Series Analysis of Sensor Signals from Power Plants
|
In this paper, we use topological data analysis techniques to construct a suitable neural network classifier for the task of learning sensor signals of entire power plants according to their reference designation system. We use representations of persistence diagrams to derive necessary preprocessing steps and visualize the large amounts of data. We derive deep architectures with one-dimensional convolutional layers combined with stacked long short-term memories as residual networks suitable for processing the persistence features. We combine three separate sub-networks, obtaining as input the time series itself and a representation of the persistent homology for the zeroth and first dimension. We give a mathematical derivation for most of the used hyper-parameters. For validation, numerical experiments were performed with sensor data from four power plants of the same construction type.
|
[
"Computer Science Archive->cs.LG",
"Electrical Engineering and Systems Science Archive->eess.SP"
] | 2021-06-03T10:52:47Z |
0908.4518
|
Tidal interaction of a small black hole in the field of a large Kerr black hole
|
The rates at which the mass and angular momentum of a small black hole change as a result of a tidal interaction with a much larger black hole are calculated to leading order in the small mass ratio. The small black hole is either rotating or nonrotating, and it moves on a circular orbit in the equatorial plane of the large Kerr black hole. The orbits are fully relativistic, and the rates are computed to all orders in the orbital velocity V < V_{isco}, which is limited only by the size of the innermost stable circular orbit. We show that as V \to V_{isco}, the rates take on a limiting value that depends only on V_{isco} and not on the spin parameter of the large black hole.
|
[
"Physics Archive->gr-qc"
] | 2009-08-31T12:24:01Z |
1407.3038
|
Transient and secular radioactive equilibrium revisited
|
The two definitions of radioactive equilibrium are revisited in this paper. The terms activity equilibrium and effective life equilibrium are proposed to take the place of currently used terms transient equilibrium and secular equilibrium. The proposed new definitions have the advantage of providing a clearer physics meaning. Besides the well known instant activity equilibrium, another class of exact effective life-time equilibrium is also discussed in this letter.
|
[
"Physics Archive->physics->physics.med-ph"
] | 2014-07-11T06:32:08Z |
1506.02433
|
Steady State of Pedestrian Flow in Bottleneck Experiments
|
Experiments with pedestrians could depend strongly on initial conditions. Comparisons of the results of such experiments require to distinguish carefully between transient state and steady state. In this work, a feasible algorithm - Cumulative Sum Control Chart - is proposed and improved to automatically detect steady states from density and speed time series of bottleneck experiments. The threshold of the detection parameter in the algorithm is calibrated using an autoregressive model. Comparing the detected steady states with previous manually selected ones, the modified algorithm gives more reproducible results. For the applications, three groups of bottleneck experiments are analysed and the steady states are detected. The study about pedestrian flow shows that the difference between the flows in all states and in steady state mainly depends on the ratio of pedestrian number to bottleneck width. When the ratio is higher than a critical value (approximately 115 persons/m), the flow in all states is almost identical with the flow in steady state. Thus we have more possibilities to compare the flows from different experiments, especially when the detection of steady states is difficult.
|
[
"Physics Archive->physics->physics.soc-ph"
] | 2015-06-08T10:46:13Z |
1610.00161
|
Towards deep learning with segregated dendrites
|
Deep learning has led to significant advances in artificial intelligence, in part, by adopting strategies motivated by neurophysiology. However, it is unclear whether deep learning could occur in the real brain. Here, we show that a deep learning algorithm that utilizes multi-compartment neurons might help us to understand how the brain optimizes cost functions. Like neocortical pyramidal neurons, neurons in our model receive sensory information and higher-order feedback in electrotonically segregated compartments. Thanks to this segregation, the neurons in different layers of the network can coordinate synaptic weight updates. As a result, the network can learn to categorize images better than a single layer network. Furthermore, we show that our algorithm takes advantage of multilayer architectures to identify useful representations---the hallmark of deep learning. This work demonstrates that deep learning can be achieved using segregated dendritic compartments, which may help to explain the dendritic morphology of neocortical pyramidal neurons.
|
[
"Quantitative Biology Archive->q-bio.NC"
] | 2016-10-01T17:37:34Z |
hep-ph/0312090
|
Complete NNLO QCD Analysis of B -> X_s l^+ l^- and Higher Order Electroweak Effects
|
We complete the next-to-next-to-leading order QCD calculation of the branching ratio for B -> X_s l^+ l^- including recent results for the three-loop anomalous dimension matrix and two-loop matrix elements. These new contributions modify the branching ratio in the low-q^2 region, BR_ll, by about +1% and -4%, respectively. We furthermore discuss the appropriate normalization of the electromagnetic coupling alpha and calculate the dominant higher order electroweak effects, showing that, due to accidental cancellations, they change BR_ll by only -1.5% if alpha(mu) is normalized at mu = O(m_b), while they shift it by about -8.5% if one uses a high scale normalization mu = O(M_W). The position of the zero of the forward-backward asymmetry, q_0^2, is changed by around +2%. After introducing a few additional improvements in order to reduce the theoretical error, we perform a comprehensive study of the uncertainty. We obtain BR_ll(1 GeV^2 <= q^2 <= 6 GeV^2) = (1.57 +- 0.16) x 10^-6 and q_0^2 = (3.76 +- 0.33) GeV^2 and note that the part of the uncertainty due to the b-quark mass can be easily reduced.
|
[
"Physics Archive->hep->hep-ph"
] | 2003-12-05T20:44:45Z |
2106.12492
|
Salt-in-Ionic-Liquid Electrolytes: Ion Network Formation and Negative Effective Charges of Alkali Metal Cations
|
Salt-in-ionic liquid electrolytes have attracted significant attention as potential electrolytes for next generation batteries largely due to their safety enhancements over typical organic electrolytes. However, recent experimental and computational studies have shown that under certain conditions alkali cations can migrate in electric fields as if they carried a net negative effective charge. In particular, alkali cations were observed to have negative transference numbers at small mole fractions of alkali metal salt that revert to the expected net positive transference numbers at large mole fractions. Simulations have provided some insights into these observations, where the formation of asymmetric ionic clusters, as well as a percolating ion network could largely explain the anomalous transport of alkali cations. However, a thermodynamic theory that captures such phenomena has not been developed, as ionic associations were typically treated via the formation of ion pairs. The theory presented herein, based on the classical polymer theories, describes thermoreversible associations between alkali cations and anions, where the formation of large, asymmetric ionic clusters and a percolating ionic network are a natural result of the theory. Furthermore, we present several general methods to calculate the effective charge of alkali cations in ionic liquids. We note that the negative effective charge is a robust prediction with respect to the parameters of the theory, and that the formation of a percolating ionic network leads to the restoration of net positive charges of the cations at large mole fractions of alkali metal salt. Overall, we find excellent qualitative agreement between our theory and molecular simulations in terms of ionic cluster statistics and the effective charges of the alkali cations.
|
[
"Physics Archive->cond-mat->cond-mat.stat-mech"
] | 2021-06-23T16:05:47Z |
2005.11532
|
The Threat to the Validity of Predictive Mutation Testing: The Impact of Uncovered Mutants
|
Predictive Mutation Testing (PMT) is a technique to predict whether a mutant will be killed by using machine learning approaches. Researchers have proposed various machine learning methods for PMT under the cross-project setting. However, they did not consider the impact of uncovered mutants. A mutant is uncovered if the statement on which the mutant is generated is not executed by any test cases. We show that uncovered mutants inflate previous PMT results. Moreover, we aim at proposing an alternative approach to improve PMT and suggesting a different interpretation for cross-project PMT. We replicated the previous PMT research. We also proposed an approach based on the combination of Random Forest and Gradient Boosting to improve the PMT results. We empirically evaluated our approach on the same 654 Java projects provided by the previous PMT literature. Our results indicate that the performance of PMT drastically decreases in terms of AUC from 0.83 to 0.51. Furthermore, PMT performs worse than random guesses on 27% of the test projects. The proposed approach improves the PMT results by achieving the average AUC value of 0.61.
|
[
"Computer Science Archive->cs.SE"
] | 2020-05-23T13:13:05Z |
2211.13439
|
Twisted carotenoids do not support efficient intramolecular singlet fission in the orange carotenoid protein
|
Singlet exciton fission is the spin-allowed generation of two triplet electronic excited states from a singlet state. Intramolecular singlet fission has been suggested to occur on individual carotenoid molecules within protein complexes, provided the conjugated backbone is twisted out-of-plane. However, this hypothesis has only been forwarded in protein complexes containing multiple carotenoids and bacteriochlorophylls in close contact. To test the hypothesis on twisted carotenoids in a 'minimal' one-carotenoid system, we study the orange carotenoid protein (OCP). OCP exists in two forms: in its orange form (OCPo), the single bound carotenoid is twisted, whereas in its red form (OCPr), the carotenoid is planar. To enable room-temperature spectroscopy on canthaxanthin-binding OCPo and OCPr without laser-induced photoconversion, we trap them in trehalose glass. Using transient absorption spectroscopy, we show that there is no evidence of long-lived triplet generation through intramolecular singlet fission, despite the canthaxanthin twist in OCPo.
|
[
"Physics Archive->physics->physics.chem-ph"
] | 2022-11-24T06:55:35Z |
2212.07284
|
MANTa: Efficient Gradient-Based Tokenization for Robust End-to-End Language Modeling
|
Static subword tokenization algorithms have been an essential component of recent works on language modeling. However, their static nature results in important flaws that degrade the models' downstream performance and robustness. In this work, we propose MANTa, a Module for Adaptive Neural TokenizAtion. MANTa is a differentiable tokenizer trained end-to-end with the language model. The resulting system offers a trade-off between the expressiveness of byte-level models and the speed of models trained using subword tokenization. In addition, our tokenizer is highly explainable since it produces an explicit segmentation of sequences into blocks. We evaluate our pre-trained model on several English datasets from different domains as well as on synthetic noise. We find that MANTa improves robustness to character perturbations and out-of-domain data. We then show that MANTa performs comparably to other models on the general-domain GLUE benchmark. Finally, we show that it is considerably faster than strictly byte-level models.
|
[
"Computer Science Archive->cs.CL"
] | 2022-12-14T15:33:44Z |
2110.03921
|
ViDT: An Efficient and Effective Fully Transformer-based Object Detector
|
Transformers are transforming the landscape of computer vision, especially for recognition tasks. Detection transformers are the first fully end-to-end learning systems for object detection, while vision transformers are the first fully transformer-based architecture for image classification. In this paper, we integrate Vision and Detection Transformers (ViDT) to build an effective and efficient object detector. ViDT introduces a reconfigured attention module to extend the recent Swin Transformer to be a standalone object detector, followed by a computationally efficient transformer decoder that exploits multi-scale features and auxiliary techniques essential to boost the detection performance without much increase in computational load. Extensive evaluation results on the Microsoft COCO benchmark dataset demonstrate that ViDT obtains the best AP and latency trade-off among existing fully transformer-based object detectors, and achieves 49.2AP owing to its high scalability for large models. We will release the code and trained models at https://github.com/naver-ai/vidt
|
[
"Computer Science Archive->cs.CV",
"Computer Science Archive->cs.LG"
] | 2021-10-08T06:32:05Z |
1601.04331
|
A Bayesian Nonparametric Markovian Model for Nonstationary Time Series
|
Stationary time series models built from parametric distributions are, in general, limited in scope due to the assumptions imposed on the residual distribution and autoregression relationship. We present a modeling approach for univariate time series data, which makes no assumptions of stationarity, and can accommodate complex dynamics and capture nonstandard distributions. The model for the transition density arises from the conditional distribution implied by a Bayesian nonparametric mixture of bivariate normals. This implies a flexible autoregressive form for the conditional transition density, defining a time-homogeneous, nonstationary, Markovian model for real-valued data indexed in discrete-time. To obtain a more computationally tractable algorithm for posterior inference, we utilize a square-root-free Cholesky decomposition of the mixture kernel covariance matrix. Results from simulated data suggest the model is able to recover challenging transition and predictive densities. We also illustrate the model on time intervals between eruptions of the Old Faithful geyser. Extensions to accommodate higher order structure and to develop a state-space model are also discussed.
|
[
"Statistics Archive->stat.ME"
] | 2016-01-17T19:37:58Z |
astro-ph/0508029
|
On the distribution of the modulation frequencies of RR Lyrae stars
|
For the first time connection between the pulsation and modulation properties of RR Lyrae stars has been detected. Based on the available data it is found that the possible range of the modulation frequencies, i.e, the possible maximum value of the modulation frequency depends on the pulsation frequency. Short period variables (P < 0.4 d) can have modulation period as short as some days, while longer period variables (P > 0.6 d) always exhibit modulation with P_mod > 20 d. We interpret this tendency with the equality of the modulation period with the surface rotation period, because similar distribution of the rotational periods is expected if an upper limit of the total angular momentum of stars leaving the RGB exists. The distribution of the projected rotational velocities of red and blue horizontal branch stars at different temperatures shows a similar behaviour as v_rot derived for RR Lyrae stars from their modulation periods. This common behaviour gives reason to identify the modulation period with the rotational period of the modulated RR Lyrae stars.
|
[
"Physics Archive->astro-ph"
] | 2005-08-01T10:01:46Z |
2303.12234
|
Pre-NeRF 360: Enriching Unbounded Appearances for Neural Radiance Fields
|
Neural radiance fields (NeRF) appeared recently as a powerful tool to generate realistic views of objects and confined areas. Still, they face serious challenges with open scenes, where the camera has unrestricted movement and content can appear at any distance. In such scenarios, current NeRF-inspired models frequently yield hazy or pixelated outputs, suffer slow training times, and might display irregularities, because of the challenging task of reconstructing an extensive scene from a limited number of images. We propose a new framework to boost the performance of NeRF-based architectures yielding significantly superior outcomes compared to the prior work. Our solution overcomes several obstacles that plagued earlier versions of NeRF, including handling multiple video inputs, selecting keyframes, and extracting poses from real-world frames that are ambiguous and symmetrical. Furthermore, we applied our framework, dubbed as "Pre-NeRF 360", to enable the use of the Nutrition5k dataset in NeRF and introduce an updated version of this dataset, known as the N5k360 dataset.
|
[
"Computer Science Archive->cs.CV"
] | 2023-03-21T23:29:38Z |
hep-lat/9411043
|
Canonical Demon Monte Carlo Renormalization Group
|
We describe a method to compute renormalized coupling constants in a Monte Carlo renormalization group calculation. It can be used, e.g., for lattice spin or gauge models. The basic idea is to simulate a joint system of block spins and canonical demons. Unlike the Microcanonical Renormalization Group of Creutz et al. it avoids systematical errors in small volumes. We present numerical results for the O(3) nonlinear sigma-model.
|
[
"Physics Archive->hep->hep-lat"
] | 1994-11-23T09:08:09Z |
1501.07387
|
Chiral-field microwave antennas (Chiral microwave near fields for far-field radiation)
|
In a single-element structure we obtain a radiation pattern with a squint due to chiral microwave near fields originated from a magnetostatic-mode ferrite disk. At the magnetostatic resonances, one has strong subwavelength localization of energy of microwave radiation. Magnetostatic oscillations in a thin ferrite disk are characterized by unique topological properties: the Poynting-vector vortices and the field helicity. The chiral-topology near fields allow obtaining unique phase structure distribution for far-field microwave radiation.
|
[
"Physics Archive->physics->physics.optics"
] | 2015-01-29T09:22:46Z |
2011.13162
|
On the diversity and frequency of code related to mathematical formulas in real-world Java projects
|
In this paper, the term formula code refers to fragments of source code that implement a mathematical formula. We present empirical studies that analyze the diversity and frequency of formula code in open-source-software projects. In an exploratory study, we investigated what kinds of formulas are implemented in real-world Java projects and derived syntactical patterns and constraints. We refined these patterns for sum and product formulas to automatically detect formula code in software archives and to reconstruct the implemented formula in mathematical notation. In a quantitative study of a large sample of engineered Java projects on GitHub we analyzed the frequency of formula code and estimated that one of 700 lines of code in this sample implements a sum or product formula. For a sample of scientific-computing projects, we found that one of 100 lines of code implements a sum or product formula. To assess the need for tool support, we investigated the helpfulness of comments for program understanding in a sample of formula-code fragments and performed an online survey. Our findings provide first insights into the characteristics of formula code, that can motivate further studies on the role of formula code in software projects and the design of formula-related tools.
|
[
"Computer Science Archive->cs.SE"
] | 2020-11-26T07:19:47Z |
cond-mat/0607170
|
Atom counting in ultra-cold gases using photoionisation and ion detection
|
We analyse photoionisation and ion detection as a means of accurately counting ultra-cold atoms. We show that it is possible to count clouds containing many thousands of atoms with accuracies better than $N^{-1/2}$ with current technology. This allows the direct probing of sub-Poissonian number statistics of atomic samples. The scheme can also be used for efficient single atom detection with high spatio-temporal resolution. All aspects of a realistic detection scheme are considered, and we discuss experimental situations in which such a scheme could be implemented.
|
[
"Physics Archive->cond-mat->cond-mat.other"
] | 2006-07-06T16:17:28Z |
1903.06692
|
On the $\mathrm{L}^p$-theory for second-order elliptic operators in divergence form with complex coefficients
|
Given a complex, elliptic coefficient function we investigate for which values of $p$ the corresponding second-order divergence form operator, complemented with Dirichlet, Neumann or mixed boundary conditions, generates a strongly continuous semigroup on $\mathrm{L}^p(\Omega)$. Additional properties like analyticity of the semigroup, $\mathrm{H}^\infty$-calculus and maximal regularity are also discussed. Finally we prove a perturbation result for real coefficients that gives the whole range of $p$'s for small imaginary parts of the coefficients. Our results are based on the recent notion of $p$-ellipticity, reverse H\"older inequalities and Gaussian estimates for the real coefficients.
|
[
"Mathematics Archive->math.AP",
"Mathematics Archive->math.FA"
] | 2019-03-15T17:45:01Z |
1302.4991
|
Optimization of Inter-Subnet Belief Updating in Multiply Sectioned Bayesian Networks
|
Recent developments show that Multiply Sectioned Bayesian Networks (MSBNs) can be used for diagnosis of natural systems as well as for model-based diagnosis of artificial systems. They can be applied to single-agent oriented reasoning systems as well as multi-agent distributed probabilistic reasoning systems. Belief propagation between a pair of subnets plays a central role in maintenance of global consistency in a MSBN. This paper studies the operation UpdateBelief, presented originally with MSBNs, for inter-subnet propagation. We analyze how the operation achieves its intended functionality, which provides hints as for how its efficiency can be improved. We then define two new versions of UpdateBelief that reduce the computation time for inter-subnet propagation. One of them is optimal in the sense that the minimum amount of computation for coordinating multi-linkage belief propagation is required. The optimization problem is solved through the solution of a graph-theoretic problem: the minimum weight open tour in a tree.
|
[
"Computer Science Archive->cs.AI"
] | 2013-02-20T15:24:20Z |
1607.03150
|
The clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: Anisotropic galaxy clustering in Fourier-space
|
We investigate the anisotropic clustering of the Baryon Oscillation Spectroscopic Survey (BOSS) Data Release 12 (DR12) sample, which consists of $1\,198\,006$ galaxies in the redshift range $0.2 < z < 0.75$ and a sky coverage of $10\,252\,$deg$^2$. We analyse this dataset in Fourier space, using the power spectrum multipoles to measure Redshift-Space Distortions (RSD) simultaneously with the Alcock-Paczynski (AP) effect and the Baryon Acoustic Oscillation (BAO) scale. We include the power spectrum monopole, quadrupole and hexadecapole in our analysis and compare our measurements with a perturbation theory based model, while properly accounting for the survey window function. To evaluate the reliability of our analysis pipeline we participate in a mock challenge, which resulted in systematic uncertainties significantly smaller than the statistical uncertainties. While the high-redshift constraint on $f\sigma_8$ at $z_{\rm eff}=0.61$ indicates a small ($\sim 1.4\sigma$) deviation from the prediction of the Planck $\Lambda$CDM model, the low-redshift constraint is in good agreement with Planck $\Lambda$CDM. This paper is part of a set that analyses the final galaxy clustering dataset from BOSS. The measurements and likelihoods presented here are combined with others in~\citet{Alam2016} to produce the final cosmological constraints from BOSS.
|
[
"Physics Archive->astro-ph->astro-ph.CO"
] | 2016-07-11T20:29:47Z |
2310.19934
|
Spectroscopic Links Among Giant Planet Irregular Satellites and Trojans
|
We collect near-infrared spectra ($\sim0.75-2.55\ \mu m$) of four Jovian irregular satellites and visible spectra ($\sim0.32-1.00\ \mu m$) of two Jovian irregular satellites, two Uranian irregular satellites, and four Neptune Trojans. We find close similarities between observed Jovian irregular satellites and previously characterized Jovian Trojans. However, irregular satellites' unique collisional histories complicate comparisons to other groups. Laboratory study of CM and CI chondrites show that grain size and regolith packing conditions strongly affect spectra of dark, carbonaceous materials. We hypothesize that different activity histories of these objects, which may have originally contained volatile ices that subsequently sublimated, could cause differences in regolith grain-size or packing properties and therefore drive spectral variation. The Uranian satellites Sycorax and Caliban appear similar to TNOs. However, we detect a feature near 0.7 $\mu m$ on Sycorax, suggesting the presence of hydrated materials. While the sample of Neptune Trojans have more neutral spectra than the Uranian satellites we observe, they remain consistent with the broad color distribution of the Kuiper belt. We detect a possible feature near 0.65-0.70 $\mu m$ on Neptune Trojan 2006 RJ103, suggesting that hydrated material may also be present in this population. Characterizing hydrated materials in the outer solar system may provide critical context regarding the origins of hydrated CI and CM chondrite meteorites. We discuss how the hydration state(s) of the irregular satellites constrains the thermal histories of the interiors of their parent bodies, which may have formed among the primordial Kuiper belt.
|
[
"Physics Archive->astro-ph->astro-ph.EP"
] | 2023-10-30T18:49:54Z |
hep-ph/0601088
|
Vacuum Polarization Effects in the Worldline Variational Approach to Quantum Field Theory
|
The worldline variational approach is extended beyond the quenched approximation, i.e. to include virtual pair production of heavy particles. This is achieved either by an expansion of the functional determinant to second order or by an hybrid ansatz for the quadratic trial action consisting of fields for the light particles and worldlines for the heavy ones as in the linear polaron model. Numerical results and analytic approximations show a reduction of radiative effects with increasing number of flavors.
|
[
"Physics Archive->hep->hep-ph"
] | 2006-01-11T16:18:09Z |
2104.11742
|
Gravitational and electromagnetic perturbations of a charged black hole in a general gauge condition
|
We derive a set of coupled equations for the gravitational and electromagnetic perturbation in the Reissner-Nordstr\"om geometry using the Newman Penrose formalism. We show that the information of the physical gravitational signal is contained in the Weyl scalar function $\Psi_4$, as is well known, but for the electromagnetic signal the information is encoded in the function $\chi$ which relates the perturbations of the radiative Maxwell scalars $\varphi_2$ and the Weyl scalar $\Psi_3$. In deriving the perturbation equations we do not impose any gauge condition and our analysis contains as a limiting case the results obtained previously for instance in Chandrashekhar's book. In our analysis, we also include the sources for the perturbations and focus on a dust-like charged fluid distribution falling radially into the black hole. Finally, by writing the functions on a basis of spin weighted spherical harmonics and the Reissner-Nordstr\"om spacetime in Kerr-Schild type coordinates a hyperbolic system of coupled partial differential equations is presented and numerically solved. In this way, we solve completely a system which generates a gravitational signal as well as an electromagnetic/gravitational one, which sets the basis to find correlations between them and thus facilitating the gravitational wave detection via the electromagnetic signal.
|
[
"Physics Archive->gr-qc"
] | 2021-04-23T17:53:03Z |
2001.06225
|
Massive discs around low-mass stars
|
We use a suite of SPH simulations to investigate the susceptibility of protoplanetary discs to the effects of self-gravity as a function of star-disc properties. We also include passive irradiation from the host star using different models for the stellar luminosities. The critical disc-to-star mass ratio for axisymmetry (for which we produce criteria) increases significantly for low-mass stars. This could have important consequences for increasing the potential mass reservoir in a proto Trappist-1 system, since even the efficient Ormel et al. (2017) formation model will be influenced by processes like external photoevaporation, which can rapidly and dramatically deplete the dust reservoir. The aforementioned scaling of the critical $M_d/M_*$ for axisymmetry occurs in part because the Toomre $Q$ parameter has a linear dependence on surface density (which promotes instability) and only an $M_*^{1/2}$ dependence on shear (which reduces instability), but also occurs because, for a given $M_d/M_*$, the thermal evolution depends on the host star mass. The early phase stellar irradiation of the disc (for which the luminosity is much higher than at the zero age main sequence, particularly at low stellar masses) can also play a key role in significantly reducing the role of self-gravity, meaning that even Solar mass stars could support axisymmetric discs a factor two higher in mass than usually considered possible. We apply our criteria to the DSHARP discs with spirals, finding that self-gravity can explain the observed spirals so long as the discs are optically thick to the host star irradiation.
|
[
"Physics Archive->astro-ph->astro-ph.EP",
"Physics Archive->astro-ph->astro-ph.GA",
"Physics Archive->astro-ph->astro-ph.SR"
] | 2020-01-17T10:18:26Z |
2103.01245
|
The Thermal Sunyaev-Zel'dovich Effect from Massive, Quiescent 0.5 $\leq$ z $\leq$ 1.5 Galaxies
|
We use combined South Pole Telescope (SPT)+Planck temperature maps to analyze the circumgalactic medium (CGM) encompassing 138,235 massive, quiescent 0.5 $\leq$ z $\leq$ 1.5 galaxies selected from data from the Dark Energy Survey (DES) and Wide-Field Infrared Survey Explorer (WISE). Images centered on these galaxies were cut from the 1.85 arcmin resolution maps with frequency bands at 95, 150, and 220 GHz. The images were stacked, filtered, and fit with a gray-body dust model to isolate the thermal Sunyaev-Zel'dovich (tSZ) signal, which is proportional to the total energy contained in the CGM of the galaxies. We separate these $M_{\star} = 10^{10.9} M_\odot$ - $10^{12} M_\odot$ galaxies into 0.1 dex stellar mass bins, detecting tSZ per bin up to $5.6\sigma$ and a total signal-to-noise ratio of $10.1\sigma$. We also detect dust with an overall signal-to-noise ratio of $9.8\sigma$, which overwhelms the tSZ at 150GHz more than in other lower-redshift studies. We correct for the $0.16$ dex uncertainty in the stellar mass measurements by parameter fitting for an unconvolved power-law energy-mass relation, $E_{\rm therm} = E_{\rm therm,peak} \left(M_\star/M_{\star,{\rm peak}} \right)^\alpha$, with the peak stellar mass distribution of our selected galaxies defined as $M_{\star,{\rm peak}}= 2.3 \times 10^{11} M_\odot$. This yields an $E_{\rm therm,peak}= 5.98_{-1.00}^{+1.02} \times 10^{60}$ erg and $\alpha=3.77_{-0.74}^{+0.60}$. These are consistent with $z \approx 0$ observations and within the limits of moderate models of active galactic nuclei (AGN) feedback. We also compute the radial profile of our full sample, which is similar to that recently measured at lower-redshift by Schaan et al. (2021).
|
[
"Physics Archive->astro-ph->astro-ph.CO",
"Physics Archive->astro-ph->astro-ph.GA"
] | 2021-03-01T19:01:15Z |
gr-qc/0405132
|
The Dynamic Space of General Relativity in Second Atomization
|
The notion that the geometry of our space-time is not only a static background but can be physically dynamic is well established in general relativity. Geometry can be described as shaped by the presence of matter, where such shaping manifests itself as gravitational force. We consider here probabilistic or atomistic models of such space-time, in which the active geometry emerges from a statistical distribution of 'atoms'. Such atoms are not to be confused with their chemical counterparts, however the shift of perspective obtained in analyzing a gas via its molecules rather than its bulk properties is analogous to this "second atomization". In this atomization, space-time itself (i.e. the meter and the second) is effectively atomized, so the atoms themselves must exist in a 'subspace'. Here we build a simple model of such a space-time from the ground up, establishing a route for more complete theories, and enabling a review of recent work. We first introduce the motivation behind statistical interpretations and atomism, and look at applications to the realm of dynamic space-time theories. We then consider models of kinetic media in subspace compatible with our understanding of light. From the equations governing the propagation of light in subspace we can build a metric geometry, describing the dynamic and physical space-time of general relativity. Finally, implications of the theory on current frontiers of general relativity including cosmology, black holes, and quantum gravity are discussed.
|
[
"Physics Archive->gr-qc"
] | 2004-05-26T18:03:24Z |
hep-lat/0402011
|
Lattice formulation of chiral gauge theories
|
We present a general formulation of chiral gauge theories, which admits Dirac operators with more general spectra, reveals considerably more possibilities for the structure of the chiral projections, and nevertheless allows appropriate realizations. In our analyses we use two forms of the correlation functions which both also apply in the presence of zero modes and for any value of the index. To account properly for the conditions on the bases the concept of equivalence classes of pairs of them is introduced. The behaviors under gauge transformations and under CP transformations are unambiguously derived.
|
[
"Physics Archive->hep->hep-lat"
] | 2004-02-11T14:01:56Z |
math-ph/0612038
|
Topological quantization of the harmonic oscillator
|
We present a derivation of the energy spectrum of the harmonic oscillator by using the alternative approach of topological quantization. The spectrum is derived from the topological invariants of a particular principal fiber bundle which can be assigned to any configuration of classical mechanics, when formulated according to Maupertuis formalism.
|
[
"Mathematics Archive->math.MP",
"Physics Archive->gr-qc",
"Physics Archive->math-ph"
] | 2006-12-13T10:43:13Z |
0909.0640
|
Exact energy spectrum of a two-temperature kinetic Ising model
|
The exact energy spectrum is developed for a two temperature kinetic Ising spin chain, and its dual reaction diffusion system with spatially alternating pair annihilation and creation rates. Symmetries of the system pseudo-Hamiltonian that enable calculation of the spectrum are also used to derive explicit state vectors for small system sizes, and to make observations regarding state vectors in the general case. Physical consequences of the surprisingly simple form for the eigenvalues are also discussed.
|
[
"Physics Archive->cond-mat->cond-mat.stat-mech"
] | 2009-09-03T13:34:42Z |
1407.2791
|
Joint Downlink Base Station Association and Power Control for Max-Min Fairness: Computation and Complexity
|
In a heterogeneous network (HetNet) with a large number of low power base stations (BSs), proper user-BS association and power control is crucial to achieving desirable system performance. In this paper, we systematically study the joint BS association and power allocation problem for a downlink cellular network under the max-min fairness criterion. First, we show that this problem is NP-hard. Second, we show that the upper bound of the optimal value can be easily computed, and propose a two-stage algorithm to find a high-quality suboptimal solution. Simulation results show that the proposed algorithm is near-optimal in the high-SNR regime. Third, we show that the problem under some additional mild assumptions can be solved to global optima in polynomial time by a semi-distributed algorithm. This result is based on a transformation of the original problem to an assignment problem with gains $\log(g_{ij})$, where $\{g_{ij}\}$ are the channel gains.
|
[
"Computer Science Archive->cs.IT",
"Mathematics Archive->math.IT"
] | 2014-07-10T14:00:18Z |
1903.02565
|
Littlest Inverse Seesaw Model
|
We propose a minimal predictive inverse seesaw model based on two right-handed neutrinos and two additional singlets, leading to the same low energy neutrino mass matrix as in the Littlest Seesaw (LS) (type I) model. In order to implement such a Littlest Inverse Seesaw (LIS) model, we have used an $S_{4}$ family symmetry, together with other various symmetries, flavons and driving fields. The resulting LIS model leads to an excellent fit to the low energy neutrino parameters, including the prediction of a normal neutrino mass ordering, exactly as in the usual LS model. However, unlike the LS model, the LIS model allows charged lepton flavour violating (CLFV) processes and lepton conversion in nuclei within reach of the forthcoming experiments.
|
[
"Physics Archive->hep->hep-ph"
] | 2019-03-06T19:00:03Z |
1702.07009
|
The Impact of Confounder Selection in Propensity Scores for Rare Events Data - with Applications to Birth Defects
|
Our work was motivated by a recent study on birth defects of infants born to pregnant women exposed to a certain medication for treating chronic diseases. Outcomes such as birth defects are rare events in the general population, which often translate to very small numbers of events in the unexposed group. As drug safety studies in pregnancy are typically observational in nature, we control for confounding in this rare events setting using propensity scores (PS). Using our empirical data, we noticed that the estimated odds ratio for birth defects due to exposure varied drastically depending on the specific approach used. The commonly used approaches with PS are matching, stratification, inverse probability weighting (IPW) and regression adjustment. The extremely rare events setting renders the matching or stratification infeasible. In addition, the PS itself may be formed via different approaches to select confounders from a relatively long list of potential confounders. We carried out simulation experiments to compare different combinations of approaches: IPW or regression adjustment, with 1) including all potential confounders without selection, 2) selection based on univariate association between the candidate variable and the outcome, 3) selection based on change in effects (CIE). The simulation showed that IPW without selection leads to extremely large variances in the estimated odds ratio, which help to explain the empirical data analysis results that we had observed. The simulation also showed that IPW with selection based on univariate association with the outcome is preferred over IPW with CIE. Regression adjustment has small variances of the estimated odds ratio regardless of the selection methods used.
|
[
"Statistics Archive->stat.AP"
] | 2017-02-22T21:21:54Z |
2212.06624
|
Polyharmonic equations involving surface measures
|
This article studies (optimal) $W^{2m-1,\infty}$-regularity for the polyharmonic equation $(-\Delta)^m u = Q \; \mathcal{H}^{n-1} \llcorner \Gamma$, where $\Gamma$ is a (suitably regular) $(n-1)$-dimensional submanifold of $\mathbb{R}^n$, $\mathcal{H}^{n-1}$ is the Hausdorff measure, and $Q$ is some suitably regular density. We extend findings in [9], where the second-order equation $-\mathrm{div}(A(x)\nabla u) = Q \; \mathcal{H}^{n-1} \llcorner \Gamma$ is studied. As an application we derive (optimal) $W^{3,\infty}$-regularity for solutions of the biharmonic Alt-Caffarelli problem in two dimensions.
|
[
"Mathematics Archive->math.AP"
] | 2022-12-13T14:55:44Z |
2208.00736
|
Zeeman optical pumping of $^{87}$Rb atoms in a hollow core photonic crystal fibre
|
Preparation of an atomic ensemble in a particular Zeeman state is a critical step of many protocols for implementing quantum sensors and quantum memories. These devices can also benefit from optical fibre integration. In this work we describe experimental results supported by a theoretical model of single-beam optical pumping of $^{87}$Rb atoms within a hollow-core photonic crystal fibre. The observed 50% population increase in the pumped F=2, m$_F$=2 Zeeman substate along with the depopulation of remaining Zeeman substates enabled us to achieve a 3 times improvement in the relative population of the m$_F$=2 substate within the F=2 manifold, with 60% of the F=2 population residing in the m$_F$=2 dark sublevel. Based on our theoretical model, we also propose methods to further improve the pumping efficiency in alkali-filled hollow-core fibres.
|
[
"Physics Archive->physics->physics.atom-ph",
"Physics Archive->physics->physics.optics"
] | 2022-08-01T10:49:52Z |
1610.03946
|
A Neural Network for Coordination Boundary Prediction
|
We propose a neural-network based model for coordination boundary prediction. The network is designed to incorporate two signals: the similarity between conjuncts and the observation that replacing the whole coordination phrase with a conjunct tends to produce a coherent sentences. The modeling makes use of several LSTM networks. The model is trained solely on conjunction annotations in a Treebank, without using external resources. We show improvements on predicting coordination boundaries on the PTB compared to two state-of-the-art parsers; as well as improvement over previous coordination boundary prediction systems on the Genia corpus.
|
[
"Computer Science Archive->cs.CL"
] | 2016-10-13T06:42:51Z |
2309.13323
|
Light correcting light with nonlinear optics
|
Structured light, where complex optical fields are tailored in all their degrees of freedom, has become highly topical of late, advanced by a sophisticated toolkit comprising both linear and nonlinear optics. Removing undesired structure from light is far less developed, leveraging mostly on inverting the distortion, e.g., with adaptive optics or the inverse transmission matrix of a complex channel, both requiring that the distortion is fully characterised through appropriate measurement. Here we show that distortions in spatially structured light can be corrected through difference frequency generation in a nonlinear crystal without any need for the distortion to be known. We demonstrate the versatility of our approach by using a wide range of aberrations and structured light modes, including higher-order orbital angular momentum (OAM) beams, showing excellent recovery of the original undistorted field. To highlight the efficacy of this process, we deploy the system in a prepare-and-measure communications link with OAM, showing minimal crosstalk even when the transmission channel is highly aberrated, and outline how the approach could be extended to alternative experimental modalities and nonlinear processes. Our demonstration of light correcting light without the need for measurement opens a new approach to measurement-free error correction for classical and quantum structured light, with direct applications in imaging, sensing and communication
|
[
"Physics Archive->physics->physics.optics"
] | 2023-09-23T09:57:05Z |
2002.08515
|
Evaporation Induced Rayleigh-Taylor Instabilities in Polymer Solutions
|
Understanding the mechanics of detrimental convective instabilities in drying polymer solutions is crucial in many applications such as the production of film coatings. It is well known that solvent evaporation in polymer solutions can lead to Rayleigh-B\'enard or Marangoni-type instabilities. Here we reveal another mechanism, namely that evaporation can cause the interface to display Rayleigh-Taylor instabilities due to the build-up of a dense layer at the air-liquid interface. We study experimentally the onset time ($t_p$) of the instability as a function of the macroscopic properties of aqueous polymer solutions, which we tune by varying the polymer concentration ($c_0$), molecular weight and polymer type. In dilute solutions, $t_p$ shows two limiting behaviors depending on the polymer diffusivity. For high diffusivity polymers (low molecular weight), the pluming time scales as $c_0^{-2/3}$. This result agrees with previous studies on gravitational instabilities in miscible systems where diffusion stabilizes the system. On the other hand, in low diffusivity polymers the pluming time scales as $c_0^{-1}$. The stabilizing effect of an effective interfacial tension, similar to those in immiscible systems, explains this strong concentration dependence. Above a critical concentration, $\hat{c}$, viscosity delays the growth of the instability, allowing time for diffusion to act as the dominant stabilizing mechanism. This results in $t_p$ scaling as $(\nu/c_0)^{2/3}$.
|
[
"Physics Archive->cond-mat->cond-mat.soft",
"Physics Archive->physics->physics.flu-dyn"
] | 2020-02-20T01:14:04Z |
1707.01511
|
MOSFIRE Spectroscopy of Galaxies in Cosmic Noon
|
The recent development of sensitive, multiplexed near infra-red instruments has presented astronomers the unique opportunity to survey mass/magnitude complete samples of galaxies at \emph{Cosmic Noon}, a time period where $\sim80\%$ of the observed baryonic mass is generated and galaxies are actively star-forming and evolving rapidly. This thesis takes advantage of the recently commissioned MOSFIRE spectrograph on Keck, to conduct a survey (ZFIRE) of galaxies at $1.5<z<2.5$ to measure accurate spectroscopic redshifts and basic galaxy properties derived from multiple emission lines. The majority of the thesis work involved survey planning, observing, data reduction, and catalogue preparation of the ZFIRE survey and is described in detail in this thesis. Using the ZFIRE spectroscopic redshifts, I show why spectroscopy is instrumental to determine fundamental galaxy properties via SED fitting techniques and to probe gravitationally bound structures in the early universe. The thesis further presents basic properties of the ZFIRE data products publicly released for the benefit of the astronomy community. The high mass-completeness of the ZFIRE spectroscopic data at $z\sim2$ makes it ideal to study fundamental galaxy properties such as, star formation rates, metallicities, inter-stellar medium properties, galaxy kinematics, and the stellar initial mass functions in unbiased star-forming galaxies. This thesis focuses on one such aspect, the IMF.
|
[
"Physics Archive->astro-ph->astro-ph.GA"
] | 2017-07-05T18:01:57Z |
cond-mat/0210625
|
Electromagnetic Wave Propagation in Media with Indefinite Permittivity and Permeability Tensors
|
We study the behavior of wave propagation in materials for which not all of the principle elements of the permeability and permittivity tensors have the same sign. We find that a wide variety of effects can be realized in such media, including negative refraction, near-field focusing and high impedance surface reflection. In particular a bi-layer of these materials can transfer a field distribution from one side to the other, including near-fields, without requiring internal exponentially growing waves.
|
[
"Physics Archive->cond-mat->cond-mat.mtrl-sci"
] | 2002-10-29T00:50:35Z |
cond-mat/0103284
|
A Micromechanical Model of Hardening, Rate Sensitivity and Thermal Softening in BCC Single Crystals
|
The present paper is concerned with the development of a micromechanical model of the hardening, rate-sensitivity and thermal softening of bcc crystals. In formulating the model we specifically consider the following unit processes: double-kink formation and thermally activated motion of kinks; the close-range interactions between primary and forest dislocations, leading to the formation of jogs; the percolation motion of dislocations through a random array of forest dislocations introducing short-range obstacles of different strengths; dislocation multiplication due to breeding by double cross-slip; and dislocation pair annihilation. The model is found to capture salient features of the behavior of Ta crystals such as: the dependence of the initial yield point on temperature and strain rate; the presence of a marked stage I of easy glide, specially at low temperatures and high strain rates; the sharp onset of stage II hardening and its tendency to shift towards lower strains, and eventually disappear, as the temperature increases or the strain rate decreases; the parabolic stage II hardening at low strain rates or high temperatures; the stage II softening at high strain rates or low temperatures; the trend towards saturation at high strains; the temperature and strain-rate dependence of the saturation stress; and the orientation dependence of the hardening rate.
|
[
"Physics Archive->cond-mat->cond-mat.mtrl-sci",
"Physics Archive->cond-mat->cond-mat.stat-mech"
] | 2001-03-13T22:51:51Z |
1608.00973
|
Chronos and Kairos: Mosfire Observations of Post-Starburst Galaxies in z~1 Clusters and Groups
|
In this study we present the exploration of $\sim$500 spectroscopically confirmed galaxies in and around two large scale structures at $z\sim1$ drawn from the ORELSE survey. A sub-sample of these galaxies ($\sim$150) were targeted for the initial phases of a near-infrared MOSFIRE spectroscopic campaign investigating the differences in selections of galaxies which had recently ended a burst of star formation or had rapidly quenched (i.e., post-starburst or K+A galaxies). Selection with MOSFIRE resulted in a post-starburst sample more than double that selected by traditional $z\sim1$ (observed-frame optical) methods even after the removal of the relatively large fraction of dusty starburst galaxies selected through traditional methods. While the traditional post-starburst fraction increased with increased global density, the MOSFIRE-selected post-starburst fraction was found to be constant in field, group, and cluster environments. However, this fraction relative to the number of galaxies with ongoing star formation was observed to elevate in the cluster environment. Post-starbursts selected with MOSFIRE were predominantly found to exhibit moderately strong [OII] emission originating from activity other than star formation. Such galaxies, termed K+A with ImposteR [OII]-derived Star formation (KAIROS) galaxies, were found to be considerably younger than traditionally-selected post-starbursts and likely undergoing some form of feedback absent or diminished in traditional post-starbursts. A comparison between the environments of the two types of post-starbursts suggests a picture in which the evolution of a post-starburst galaxy is considerably different in cluster environments than in the more rarefied environments of a group or the field.
|
[
"Physics Archive->astro-ph->astro-ph.GA"
] | 2016-08-02T20:00:02Z |
2002.12017
|
Meta-Learned Confidence for Few-shot Learning
|
Transductive inference is an effective means of tackling the data deficiency problem in few-shot learning settings. A popular transductive inference technique for few-shot metric-based approaches, is to update the prototype of each class with the mean of the most confident query examples, or confidence-weighted average of all the query samples. However, a caveat here is that the model confidence may be unreliable, which may lead to incorrect predictions. To tackle this issue, we propose to meta-learn the confidence for each query sample, to assign optimal weights to unlabeled queries such that they improve the model's transductive inference performance on unseen tasks. We achieve this by meta-learning an input-adaptive distance metric over a task distribution under various model and data perturbations, which will enforce consistency on the model predictions under diverse uncertainties for unseen tasks. Moreover, we additionally suggest a regularization which explicitly enforces the consistency on the predictions across the different dimensions of a high-dimensional embedding vector. We validate our few-shot learning model with meta-learned confidence on four benchmark datasets, on which it largely outperforms strong recent baselines and obtains new state-of-the-art results. Further application on semi-supervised few-shot learning tasks also yields significant performance improvements over the baselines. The source code of our algorithm is available at https://github.com/seongmin-kye/MCT.
|
[
"Computer Science Archive->cs.CV",
"Computer Science Archive->cs.LG",
"Statistics Archive->stat.ML"
] | 2020-02-27T10:22:17Z |
hep-ph/9903221
|
Colour Octet Contribution in Exclusive P-Wave Charmonium Decay into Proton-Antiproton
|
In inclusive P-wave charmonium decay, to cancel infrared divergence in the colour singlet contribution requires the inclusion of the colour octet which becomes degenerate with the former in the infrared limit. In the corresponding exclusive decay, such an infrared divergence does not exist. On this ground, it becomes doubtful whether the colour octet is needed in exclusive reactions. A contradiction in the underlying picture, however, would result once all strong decay channels are summed. We provide an answer to this question in support of the colour octet with theoretical arguments as well as an explicit calculation of Chi_J ---> p \bar p.
|
[
"Physics Archive->hep->hep-ex",
"Physics Archive->hep->hep-ph"
] | 1999-03-01T22:58:51Z |
1309.6913
|
Dynamical symmetries of the Kepler problem
|
This work originates from a first year undergraduate research project on hidden symmetries of the dynamics for classical Hamiltonian systems, under the program 'Jovens talentos para a Ciencia' of Brazilian funding agency Capes. For pedagogical reasons the main subject chosen was Kepler's problem of motion under a central potential, since it is a completely solved system. It is well known that for this problem the group of dynamical symmetries is strictly larger than the isometry group O(3), the extra symmetries corresponding to hidden symmetries of the dynamics. By taking the point of view of examining the group action of the dynamical symmetries on the allowed trajectories, it is possible to teach in the same project basic elements of as many important subjects in physics as: Hamiltonian formalism, hidden symmetries, integrable systems, group theory, and the use of manifolds.
|
[
"Physics Archive->physics->physics.class-ph"
] | 2013-09-22T01:31:31Z |
astro-ph/9909379
|
An intrinsic anisotropy in the angular distribution of gamma-ray bursts
|
The anisotropy of the sky distribution of 2025 gamma-ray bursts (GRBs) collected in Current BATSE catalog is confirmed. It is shown that the quadrupole term being proportional to $\sim \sin 2b \sin l$ is non-zero with a probability 99.9%. The occurrence of this anisotropy term is then supported by the binomial test even with the probability 99.97%. It is also argued that this anisotropy cannot be caused exclusively by instrumental effects due to the non-uniform sky exposure of BATSE instrument; there should exist also some intrinsic anisotropy in the angular distribution of GRBs. Separating GRBs into short and long subclasses, it is shown that the 251 short ones are distributed anisotropically, but the 681 long ones seem to be distributed still isotropically. The 2-sample Kolmogorov-Smirnov test shows that they are distributed differently with a 98.7% probability. The character of anisotropy suggests that the cosmological origin of short GRBs further holds, and there is no evidence for their Galactical origin. The work in essence contains the key ideas and results of a recently published paper (\cite{balazs}), to which the new result following from the 2-sample Kolmogorov-Smirnov test is added, too.
|
[
"Physics Archive->astro-ph"
] | 1999-09-22T16:12:32Z |
1006.5799
|
A New Galactic Extinction Map of the Cygnus Region
|
We have made a Galactic extinction map of the Cygnus region with 5' spatial resolution. The selected area is 80^\circ to 90^\circ in the Galactic longitude and -4^\circ to 8^\circ in the Galactic latitude. The intensity at 140 \mum is derived from the intensities at 60 and 100 \mum of the IRAS data using the tight correlation between 60, 100, and 140 \mum found in the Galactic plane. The dust temperature and optical depth are calculated with 5' resolution from the 140 and 100 \mum intensity, and Av is calculated from the optical depth. In the selected area, the mean dust temperature is 17 K, the minimum is 16 K, and the maximum is 30 K. The mean Av is 6.5 mag, the minimum is 0.5 mag, and the maximum is 11 mag. The dust temperature distribution shows significant spatial variation on smaller scales down to 5'. Because the present study can trace the 5'-scale spatial variation of the extinction, it has an advantage over the previous studies, such as the one by Schlegel, Finkbeiner, & Davis, who used the COBE/DIRBE data to derive the dust temperature distribution with a spatial resolution of 1^\circ. The difference of Av between our map and Schlegel et al.'s is \pm 3 mag. A new extinction map of the entire sky can be produced by applying the present method.
|
[
"Physics Archive->astro-ph->astro-ph.GA"
] | 2010-06-30T08:21:19Z |
1002.1145
|
A unified solution for the orbit and light-time effect in the V505 Sgr system
|
The multiple system V505 Sagittarii is composed of at least three stars: a compact eclipsing pair and a distant component, which orbit is measured directly using speckle interferometry. In order to explain the observed orbit of the third body in V505 Sagittarii and also other observable quantities, namely the minima timings of the eclipsing binary and two different radial velocities in the spectrum, we thoroughly test a fourth-body hypothesis - a perturbation by a dim, yet-unobserved object. We use an N-body numerical integrator to simulate future and past orbital evolution of 3 or 4 components in this system. We construct a suitable chi^2 metric from all available speckle-interferometry, minima-timings and radial-velocity data and we scan a part of a parameter space to get at least some of allowed solutions. In principle, we are able to explain all observable quantities by a presence of a fourth body, but the resulting likelihood of this hypothesis is very low. We also discuss other theoretical explanations of the minima timings variations. Further observations of the minima timings during the next decade or high-resolution spectroscopic data can significantly constrain the model.
|
[
"Physics Archive->astro-ph->astro-ph.SR"
] | 2010-02-05T08:28:19Z |
1811.12129
|
Evidence of Interfacial Topological Superconductivity on the Topological Semimetal Tungsten Carbide Induced by Metal Deposition
|
Interfaces between materials with different electronic ground states have become powerful platforms for creating and controlling novel quantum states of matter, in which inversion symmetry breaking and other effects at the interface may introduce additional electronic states. Among the emergent phenomena, superconductivity is of particular interest. In this work, by depositing metal films on a newly identified topological semimetal tungsten carbide (WC) single crystal, we have obtained interfacial topological superconductivity evidenced from soft point contact spectroscopy. This very robust phenomenon has been demonstrated for a wide range of Metal/WC interfaces, involving both non-magnetic and ferromagnetic films, and the superconducting transition temperatures is surprisingly insensitive to the magnetism of thin films, suggesting a spin-triplet pairing superconducting state. The results offer an opportunity to implement topological superconductivity using convenient thin film coating method.
|
[
"Physics Archive->cond-mat->cond-mat.mtrl-sci",
"Physics Archive->cond-mat->cond-mat.supr-con"
] | 2018-11-29T13:26:26Z |
2007.05604
|
Near-field Radiative Heat Transfer in Many-Body Systems
|
Many-body physics aims to understand emergent properties of systems made of many interacting objects. This article reviews recent progress on the topic of radiative heat transfer in many-body systems consisting of thermal emitters interacting in the near-field regime. Near-field radiative heat transfer is a rapidly emerging field of research in which the cooperative behavior of emitters gives rise to peculiar effects which can be exploited to control heat flow at the nanoscale. Using an extension of the standard Polder and van Hove stochastic formalism to deal with thermally generated fields in $N$-body systems, along with their mutual interactions through multiple scattering, a generalized Landauer-like theory is derived to describe heat exchange mediated by thermal photons in arbitrary reciprocal and non-reciprocal multi-terminal systems. In this review, we use this formalism to address both transport and dynamics in these systems from a unified perspective. Our discussion covers: (i) the description of non-additivity of heat flux and its related effects, including fundamental limits as well as the role of nanostructuring and material choice, (ii) the study of equilibrium states and multistable states, (iii) the relaxation dynamics (thermalization) toward local and global equilibria, (iv) the analysis of heat transport regimes in ordered and disordered systems comprised of a large number of objects, density and range of interactions, and (v) the description of thermomagnetic effects in magneto-optical systems and heat transport mechanisms in non-Hermitian many-body systems. We conclude this review by listing outstanding challenges and promising future research directions.
|
[
"Physics Archive->cond-mat->cond-mat.mes-hall"
] | 2020-07-10T20:47:56Z |
0710.3037
|
The Stellar Population of the Chamaeleon I Star-Forming Region
|
I present a new census of the stellar population in the Chamaeleon I star-forming region. Using optical and near-IR photometry and followup spectroscopy, I have discovered 50 new members of Chamaeleon I, expanding the census of known members to 226 objects. Fourteen of these new members have spectral types later than M6, which doubles the number of known members that are likely to be substellar. I have estimated extinctions, luminosities, and effective temperatures for the known members, used these data to construct an H-R diagram for the cluster, and inferred individual masses and ages with the theoretical evolutionary models of Baraffe and Chabrier. The distribution of isochronal ages indicates that star formation began 3-4 and 5-6 Myr ago in the southern and northern subclusters, respectively, and has continued to the present time at a declining rate. The IMF in Chamaeleon I reaches a maximum at a mass of 0.1-0.15 M_sun, and thus closely resembles the IMFs in IC 348 and the Orion Nebula Cluster. In logarithmic units where the Salpeter slope is 1.35, the IMF is roughly flat in the substellar regime and shows no indication of reaching a minimum down to a completeness limit of 0.01 M_sun. The low-mass stars are more widely distributed than members at other masses in the northern subcluster, but this is not the case in the southern subcluster. Meanwhile, the brown dwarfs have the same spatial distribution as the stars out to a radius of 3 deg (8.5 pc) from the center of Chamaeleon I.
|
[
"Physics Archive->astro-ph"
] | 2007-10-16T12:44:04Z |
1907.10464
|
Collective modes in pumped unconventional superconductors with competing ground states
|
Motivated by the recent development of terahertz pump-probe experiments, we investigate the short-time dynamics in superconductors with multiple attractive pairing channels. Studying a single-band square lattice model with spin-spin interaction as an example, we find the signatures of collective excitations of the pairing symmetries (known as Bardasis-Schrieffer modes) as well as the order parameter amplitude (Higgs mode) in the short-time dynamics of the spectral gap and quasiparticle distribution after an excitation by a pump pulse. We show that the polarization and intensity of the pulse can be used to control the symmetry of the non-equilibrium state as well as frequencies and relative intensities of the contributions of different collective modes. We find particularly strong signatures of the Bardasis-Schrieffer mode in the dynamics of the quasiparticle distribution function. Our work shows the potential of modern ultrafast experiments to address the collective excitations in unconventional superconductors and highlights the importance of sub-dominant interactions for the non-equilibrium dynamics in these systems.
|
[
"Physics Archive->cond-mat->cond-mat.str-el",
"Physics Archive->cond-mat->cond-mat.supr-con"
] | 2019-07-24T14:29:54Z |
2203.06283
|
Prediction of stable Li-Sn compounds: boosting ab initio searches with neural network potentials
|
The Li-Sn binary system has been the focus of extensive research because it features Li-rich alloys with potential applications as battery anodes. Our present re-examination of the binary system with a combination of machine learning and ab initio methods has allowed us to screen a vast configuration space and uncover a number of overlooked thermodynamically stable alloys. At ambient pressure, our evolutionary searches identified a new stable Li$_3$Sn phase with a large BCC-based hR48 structure and a possible high-T LiSn$_4$ ground state. By building a simple model for the observed and predicted Li-Sn BCC alloys we constructed an even larger viable hR75 structure at an exotic 19:6 stoichiometry. At 20 GPa, new 11:2, 5:1, and 9:2 phases found with our global searches destabilize previously proposed phases with high Li content. The findings showcase the appreciable promise machine learning interatomic potentials hold for accelerating ab initio prediction of complex materials.
|
[
"Physics Archive->cond-mat->cond-mat.mtrl-sci",
"Physics Archive->physics->physics.comp-ph"
] | 2022-03-11T23:34:23Z |
hep-lat/0409132
|
Light hadron spectra and wave functions in quenched QCD with overlap quarks on a large lattice
|
A simulation of quenched QCD with the overlap Dirac operator has been completed using 100 Wilson gauge configurations at beta=6 on an 18^3x64 lattice. We present results for meson and baryon masses, meson final state "wave functions'' and other observables.
|
[
"Physics Archive->hep->hep-lat"
] | 2004-09-21T13:02:39Z |
1208.1468
|
Summary of the Electroweak and Searches Working Group
|
The working group on electroweak measurements and searches for new physics at the Deep Inelastic Scattering 2012 workshop covered a wide range of results from the various experiments at the LHC (ATLAS, CMS, LHCb), the Tevatron (CDF, DO) and HERA (H1, ZEUS), as well as results from the BaBar, NA48/62 and OPERA collaborations. In addition, invited theoretical overviews were presented and discussed in each of the sessions. A summary of a selection of the results shown at the conference is given.
|
[
"Physics Archive->hep->hep-ex",
"Physics Archive->hep->hep-ph"
] | 2012-08-07T16:59:21Z |
0806.1290
|
New absolute magnitude calibrations for detached binaries
|
Lutz-Kelker bias corrected absolute magnitude calibrations for the detached binary systems with main-sequence components are presented. The absolute magnitudes of the calibrator stars were derived at intrinsic colours of Johnson-Cousins and 2MASS (Two Micron All Sky Survey) photometric systems. As for the calibrator stars, 44 detached binaries were selected from the Hipparcos catalogue, which have relative observed parallax errors smaller than 15% ($\sigma_{\pi}/\pi\leq0.15$). The calibration equations which provide the corrected absolute magnitude for optical and near-infrared pass bands are valid for wide ranges of colours and absolute magnitudes: $-0.18<(B-V)_{0}<0.91$, $-1.6<M_{V}<5.5$ and $-0.15<(J-H)_{0}<0.50$, $-0.02<(H-K_{s})_{0}<0.13$, $0<M_{J}<4$, respectively. The distances computed using the luminosity-colours (LCs) relation with optical (BV) and near-infrared ($JHK_{s}$) observations were compared to the distances found from various other methods. The results show that new absolute magnitude calibrations of this study can be used as a convenient statistical tool to estimate the true distances of detached binaries out of Hipparcos' distance limit.
|
[
"Physics Archive->astro-ph"
] | 2008-06-07T16:28:39Z |
1402.2019
|
Authoris: a tool for authority control in the semantic web
|
Purpose: The purpose of this paper is to propose a tool that generates authority files to be integrated with linked data by means of learning rules. AUTHORIS is software developed to enhance authority control and information exchange among bibliographic and non-bibliographic entities. Design / methodology / approach: The article analyzes different methods previously developed for authority control as well as IFLA and ALA standards for managing bibliographic records. Semantic Web technologies are also evaluated. AUTHORIS relies on Drupal and incorporates the protocols of Dublin Core, SIOC, SKOS and FOAF. The tool has also taken into account the obsolescence of MARC and its substitution by FRBR and RDA. Its effectiveness was evaluated applying a learning test proposed by RDA. Over 80 percent of the actions were carried out correctly. Findings: The use of learning rules and the facilities of linked data make it easier for information organizations to reutilize products for authority control and distribute them in a fair and efficient manner. Research limitations / implications: The ISAD-G records were the ones presenting most errors. EAD was found to be second in the number of errors produced. The rest of the formats --MARC 21, Dublin Core, FRAD, RDF, OWL, XBRL and FOAF-- showed fewer than 20 errors in total. Practical implications: AUTHORIS offers institutions the means of sharing data with a high level of stability, helping to detect records that are duplicated and contributing to lexical disambiguation and data enrichment. Originality / value: The software combines the facilities of linked data, the potency of the algorithms for converting bibliographic data, and the precision of learning rules.
|
[
"Computer Science Archive->cs.DL"
] | 2014-02-10T02:33:03Z |
0812.2598
|
Ubiquitous H-alpha polarized line profiles: absorptive spectropolarimetric effects and temporal variability in Post-AGB, Herbig Ae/Be and other stellar types
|
We show here that the absorptive H-alpha polarized line profile previously seen in many Herbig Ae/Be (HAeBe) stars is a nearly ubiquitous feature of other types of embedded or obscured stars. This characteristic 1% linear polarization variation across the absorptive part of the H-alpha line is seen in Post-AGB stars as well as RV-Tau, Delta-Scuti, and other types. Each of these stars shows evidence of obscuration by intervening circumstellar hydrogen gas and the polarization effect is in the absorptive component, consistent with an optical pumping model. We present ESPaDOnS spectropolarimetric observations of 9 post-AGB and RV-Tau types in addition to many multi-epoch HiVIS observations of these targets. We find significant polarization changes across the H-alpha line in 8/9 stars with polarization amplitudes of 0.5% to over 3% (5/6 Post-AGB and 3/3 RV-Tau). In all but one of these, the polarization change is dominated by the absorptive component of the line profile. There is no evidence that subclasses of obscured stars showing stellar pulsations (RV-Tau for Post-AGB stars and Delta-Scuti for Herbig Ae/Be stars) show significant spectropolarimetric differences from the main class. Significant temporal variability is evident from both HiVIS and ESPaDOnS data for several stars presented here: 89 Her, AC Her, SS Lep, MWC 120, AB Aurigae and HD144668. The morphologies and temporal variability are comparable to existing large samples of Herbig Ae/Be and Be type stars. Since Post-AGB stars have circumstellar gas that is very different from Be stars, we discuss these observations in the context of their differing environments.
|
[
"Physics Archive->astro-ph"
] | 2008-12-14T01:44:03Z |
2305.10612
|
Accelerating MPI Collectives with Process-in-Process-based Multi-object Techniques
|
In the exascale computing era, optimizing MPI collective performance in high-performance computing (HPC) applications is critical. Current algorithms face performance degradation due to system call overhead, page faults, or data-copy latency, affecting HPC applications' efficiency and scalability. To address these issues, we propose PiP-MColl, a Process-in-Process-based Multi-object Inter-process MPI Collective design that maximizes small message MPI collective performance at scale. PiP-MColl features efficient multiple sender and receiver collective algorithms and leverages Process-in-Process shared memory techniques to eliminate unnecessary system call, page fault overhead, and extra data copy, improving intra- and inter-node message rate and throughput. Our design also boosts performance for larger messages, resulting in comprehensive improvement for various message sizes. Experimental results show that PiP-MColl outperforms popular MPI libraries, including OpenMPI, MVAPICH2, and Intel MPI, by up to 4.6X for MPI collectives like MPI_Scatter and MPI_Allgather.
|
[
"Computer Science Archive->cs.DC"
] | 2023-05-17T23:44:16Z |
1212.0417
|
An inverse iteration method for eigenvalue problems with eigenvector nonlinearities
|
Consider a symmetric matrix $A(v)\in\RR^{n\times n}$ depending on a vector $v\in\RR^n$ and satisfying the property $A(\alpha v)=A(v)$ for any $\alpha\in\RR\backslash{0}$. We will here study the problem of finding $(\lambda,v)\in\RR\times \RR^n\backslash\{0\}$ such that $(\lambda,v)$ is an eigenpair of the matrix $A(v)$ and we propose a generalization of inverse iteration for eigenvalue problems with this type of eigenvector nonlinearity. The convergence of the proposed method is studied and several convergence properties are shown to be analogous to inverse iteration for standard eigenvalue problems, including local convergence properties. The algorithm is also shown to be equivalent to a particular discretization of an associated ordinary differential equation, if the shift is chosen in a particular way. The algorithm is adapted to a variant of the Schr\"odinger equation known as the Gross-Pitaevskii equation. We use numerical simulations toillustrate the convergence properties, as well as the efficiency of the algorithm and the adaption.
|
[
"Computer Science Archive->cs.NA",
"Mathematics Archive->math.NA"
] | 2012-12-03T15:31:14Z |
1003.0188
|
History of applications of martingales in survival analysis
|
The paper traces the development of the use of martingale methods in survival analysis from the mid 1970's to the early 1990's. This development was initiated by Aalen's Berkeley PhD-thesis in 1975, progressed through the work on estimation of Markov transition probabilities, non-parametric tests and Cox's regression model in the late 1970's and early 1980's, and it was consolidated in the early 1990's with the publication of the monographs by Fleming and Harrington (1991) and Andersen, Borgan, Gill and Keiding (1993). The development was made possible by an unusually fast technology transfer of pure mathematical concepts, primarily from French probability, into practical biostatistical methodology, and we attempt to outline some of the personal relationships that helped this happen. We also point out that survival analysis was ready for this development since the martingale ideas inherent in the deep understanding of temporal development so intrinsic to the French theory of processes were already quite close to the surface in survival analysis.
|
[
"Statistics Archive->stat.ME"
] | 2010-02-28T16:11:25Z |
2208.05103
|
Modelling Socio-ecological Systems: Implementation of an Advanced Fuzzy Cognitive Map Framework for Policy development for addressing complex real-life challenges
|
This study implements a novel Fuzzy Cognitive Map (FCM) framework for addressing large complex socio-ecological problems. These are characterized as qualitative, dominated by uncertainty, human involvement with different and vague perceptions/expectations, and complex systems dynamics due to feedback relations. The FCM framework provides a participatory soft computing approach to develop consensus solutions. We demonstrate its implementation in a case study: a national-scale acute water scarcity crisis. The model has eight steps starting from collecting data from stakeholders in the form of FCMs (bi-directional graphs) represented by nodes and imprecise connections. All subsequent steps operate within a new fuzzy 2-tuple framework that overcomes previous FCM limitations through advanced processing methods, where large FCMs are fuzzified and analyzed, condensed, and aggregated using graph-theoretic measures. FCMs are simulated as Auto-Associative Neural Networks (AANN) to assess policy solutions to address the problem. In this study, very large cognitive maps were developed through interviews capturing perceptions of five different stakeholder groups taking into consideration the causes, consequences and challenges of the acute water scarcity problem in Jordan. The complex FCMs containing 186 variables comprehensively covered all aspects of water scarcity. FCMs were condensed into smaller maps in two levels. They were also combined into five stakeholder group FCMs and one whole system FCM (total 123 FCMs). AANN simulations of policy scenarios were conducted on the whole system FCM, first at the most condensed level and then moved top-down through the next two levels of granularity to explore potential solutions. These were ranked by a novel fuzzy Appropriateness criterion to provide a number of high level and effective strategies to mitigate the water crisis.
|
[
"Computer Science Archive->cs.SI"
] | 2022-08-10T01:52:03Z |
cond-mat/0203339
|
Modeling Subsurface Charge Accumulation Images of a Quantum Hall Liquid
|
Subsurface Charge Accumulation imaging is a cryogenic scanning probe technique that has recently been used to spatially probe incompressible strips formed in a two-dimensional electron system (2DES) at high magnetic fields. In this paper, we present detailed numerical modeling of these data. At a basic level, the method produces results that agree well with the predictions of models based on simple circuit elements. Moreover, the modeling method is sufficiently advanced to simulate the spatially resolved measurements. By comparing directly the simulations to the experimentally measured data, we can extract quantitatively local electronic features of the 2DES. In particular, we deduce the electron density of states inside the incompressible strips and electrical resistance across them.
|
[
"Physics Archive->cond-mat->cond-mat.mes-hall"
] | 2002-03-16T03:41:22Z |
1812.08472
|
Distributions Frames and bases
|
In this paper we will consider, in the abstract setting of rigged Hilbert spaces, distribution valued functions and we will investigate, in particular, conditions for them to constitute a "continuous basis" for the smallest space $\mathcal D$ of a rigged Hilbert space. This analysis requires suitable extensions of familiar notions as those of frame, Riesz basis and orthonormal basis. A motivation for this study comes from the Gel'fand-Maurin theorem which states, under certain conditions, the existence of a family of generalized eigenvectors of an essentially self-adjoint operator on a domain $\mathcal D$ which acts like an orthonormal basis of the Hilbert space $\mathcal H$. The corresponding object will be called here a {\em Gel'fand distribution basis}. The main results are obtained in terms of properties of a conveniently defined {\em synthesis operator}.
|
[
"Mathematics Archive->math.FA"
] | 2018-12-20T10:35:49Z |
2303.09742
|
A proof of a conjecture on the distance spectral radius
|
A cactus is a connected graph in which any two cycles have at most one common vertex. We determine the unique graph that maximizes the distance spectral radius over all cacti with fixed numbers of vertices and cycles, and thus prove a conjecture on the distance spectral radius of cacti in [S.S. Bose, M. Nath, S. Paul, On the distance spectral radius of cacti, Linear Algebra Appl. 437 (2012) 2128--2141]. We prove the result in the context of hypertrees.
|
[
"Mathematics Archive->math.CO"
] | 2023-03-17T02:43:28Z |
1602.05853
|
XBF: Scaling up Bloom-filter-based Source Routing
|
A well known drawback of IP-multicast is that it requires per-group state to be stored in the routers. Bloom-filter based source-routed multicast remedies this problem by moving the state from the routers to the packets. However, a fixed sized Bloom-filter can only store a limited number of items before the false positive ratio grows too high implying scalability issues. Several proposals have tried to address these scalability issues in Bloom-filter forwarding. These proposals, however, unnecessarily increase the forwarding complexity. In this paper, we present Extensible-Bloom-filter (XBF), a new framing and forwarding solution which effectively circumvents the aforementioned drawbacks. XBF partitions a network into sub-networks that reflect the network topology and traffic patterns, and uses a separate fixed-length Bloom-filter in each of these. We formulate this partition assignment problem into a balanced edge partitioning problem, and evaluate it with simulations on realistic topologies. Our results show that XBF scales to very large networks with minimal overhead and completely eliminates the false-positives that have plagued the traditional Bloom-filter-based forwarding protocols. It furthermore integrates with SDN environments, making it highly suitable for deployments in off-the-shelf SDN-based networks.
|
[
"Computer Science Archive->cs.NI"
] | 2016-02-18T16:09:45Z |
2007.08172
|
Lyman-alpha radiative transfer: Modeling spectrum and surface brightness profile of Lyman-alpha emitting galaxies at z=3-6
|
We perform Lyman-alpha radiative transfer calculations for reproducing Lyman-alpha properties of star-forming galaxies at high redshifts. We model a galaxy as a halo in which the density distributions of Lyman-alpha sources and H I plus dust medium are described with exponential functions. We also consider an outflow of the medium that represents a momentum-driven wind in a gravitational potential well. We successfully reproduce both the spectra and the surface brightness profiles of eight star-forming galaxies at z =3-6 observed with MUSE using this outflowing halo model with Lyman-alpha scattering. The best-fit model parameters (i.e., the outflowing velocity and optical depth) for these galaxies are consistent with other studies. We examine the impacts of individual model parameters and input spectrum on emerging spectrum and surface brightness profile. Further investigations on correlations among observables (i.e., the spatial extent of Lyman-alpha halos and Lyman-alpha spectral features) and model parameters, and spatially resolved spectra are presented as well. We demonstrate that the combination of spectrum and surface brightness profile provides strong constraints on model parameters and thus spatial/kinematic distributions of medium.
|
[
"Physics Archive->astro-ph->astro-ph.GA"
] | 2020-07-16T08:20:00Z |
cond-mat/0701177
|
Domains in Three-dimensional Ferroelectric Nanostructures: Theory and Experiment
|
Ferroelectric random access memory cells (FeRAMs) have reached 450 x 400 nm production (0.18 micron^2) at Samsung with lead zirconate-titanate (PZT), 0.13 micron^2 at Matsushita with strontium bismuth tantalate (SBT), and comparable sizes at Fujitsu with BiFeO3. However, in order to increase storage density, the industry roadmap requires by 2010 that such planar devices be replaced with three-dimensional structures. Unfortunately, little is known yet about even such basic questions as the domain scaling of 3-d nanodevices, as opposed to 2-d thin films. Here we report the experimental measurement of nano-domains in ferroelectric nanocolumns, together with a theory of domain size in 3-d structures which explains the observations.
|
[
"Physics Archive->cond-mat->cond-mat.mtrl-sci"
] | 2007-01-09T16:00:56Z |
1804.11298
|
Determination of weak values of quantum operators using only strong measurements
|
Weak values have been shown to be helpful especially when considering them as the outcomes of weak measurements. In this paper we show that in principle, the real and imaginary parts of the weak value of any operator may be elucidated from expectation values of suitably defined density, flux and hermitian commutator operators. Expectation values are the outcomes of strong (projective) measurements implying that weak values are general properties of operators in association with pre- and post-selection and they need not be preferentially associated with weak measurements. They should be considered as an important measurable property which provides added information as compared with the "standard" diagonal expectation value of an operator. As a first specific example we consider the determination of the real and imaginary parts of the weak value of the momentum operator employing projective time of flight experiments. Then the results are analyzed from the point of view of Bohmian mechanics. Finally we consider recent neutron interferometry experiments used to determine the weak values of the neutron spin.
|
[
"Physics Archive->quant-ph"
] | 2018-04-30T16:20:25Z |
1509.04079
|
Lowering the hydrogen desorption temperature of NH3BH3 through B-group substitutions
|
We present ab initio results for substitutions in the promising hydrogen-storage material NH3BH3 to lower its hydrogen desorption temperature. Substitutions have already been investigated with significant success recently, but in all cases a less electronegative element is substituted for the protic hydrogen in the NH3 group of NH3BH3. We propose a different route, substituting th ehydridic hydrogen in the BH3 group with a more electronegative element. To keep the gravimetric density high, we focus on the second period elements C, N, O, and F, all with higher electronegativity compared to H. In addition, we investigate Cu and S as possible substitutions. Our main results include Bader charge analyses, hydrogen binding energies, and kinetic barriers for the hydrogen release reaction in the gas phase as well as in the solid. While the different substituents show varying effects on the kinetic barrier and thus desorption temperature - some overshoot our goal while others have little effect - we identify Cu as a very promising substituent, which lowers the reaction barrier by approximately 37% compared to NH3BH3 and thus significantly influences the hydrogen desorption temperature.
|
[
"Physics Archive->cond-mat->cond-mat.mtrl-sci"
] | 2015-09-14T13:13:43Z |
1508.01872
|
Alleviating Merge Conflicts with Fine-grained Visual Awareness
|
Merge conflicts created by software team members working on the same code can be costly to resolve, and adversely affect productivity. In this work, we suggest the approach of fine-grained merge conflict awareness, where software team members are notified of potential merge conflicts via graphical decoration of the relevant semantic elements, in near real-time. The novelty of this approach is that it allows software developers to pinpoint the element in conflict, such as a method's body, parameter, return value, and so on, promoting communication about conflicting changes soon after they take place and on a semantic level. We have also conducted a preliminary qualitative evaluation of our approach, the results of which we report in this paper.
|
[
"Computer Science Archive->cs.SE"
] | 2015-08-08T08:38:56Z |
2006.00964
|
Berezinskii-Kosterlitz-Thouless Phase in Two-dimensional Ferroelectrics
|
The celebrated Berezinskii-Kosterlitz-Thouless (BKT) phase transition refers to a topological transition characterized, e.g., by the dissociation of vortex-antivortex pairs in two-dimensional (2D) systems. Such unusual phase has been reported in various types of materials, but never in the new class of systems made by one-unit-cell-thick (1UC) ferroelectrics (also coined as 2D ferroelectrics). Here, the use of a first-principles-based effective Hamiltonian method leads to the discovery of many fingerprints of a BKT phase existing in-between the ferroelectric and paraelectric states of 1UC tin tellurium being fully relaxed. Moreover, epitaxial strain is found to have dramatic consequences on the temperature range of such BKT phase for the 1UC SnTe. Consequently, our predictions extend the playground of BKT theory to a novel class of functional materials, and demonstrate that strain is an effective tool to alter BKT characteristics there.
|
[
"Physics Archive->cond-mat->cond-mat.mtrl-sci"
] | 2020-06-01T14:21:33Z |
cond-mat/0407656
|
Orbital ordering in manganites in the band approach
|
We consider the orbital ordering in LaMnO3 and similar systems, proceeding from the band picture. We show that for the realistic magnetic structure of A-type there exists a complete nesting betweeen two e_g-bands. As a result there occurs an instability towards an excitonic insulator-like state -- an electron-hole pairing with the wave vector Q=(\pi,\pi), which opens a gap in the spectrum and makes the system insulating. In the resulting state there appeasr an orbital ordering -- orbital density wave (ODW), the type of which coincides with those existing in LaMnO3.
|
[
"Physics Archive->cond-mat->cond-mat.stat-mech",
"Physics Archive->cond-mat->cond-mat.str-el"
] | 2004-07-25T20:40:30Z |
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