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the study of the longitudinal polarization of lambda and lambda - bar hyperons produced in polarized deep inelastic scattering, neutrino scattering, and in z0 decays allows to access the spin dynamics of the quark fragmentation process. different phenomenological spin transfer mechanisms are considered and predictions for the lambda and lambda - bar longitudinal polarization in various processes using unpolarized and polarized targets are made. current and future semi - inclusive deep inelastic scattering experiments will provide soon accurate enough data to study these phenomena and distinguish between various models for the spin transfer mechanisms.
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arxiv:hep-ph/9701384
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this work presents a conceptual synthesis of causal discovery and inference frameworks, with a focus on how foundational assumptions - - causal sufficiency, causal faithfulness, and the causal markov condition - - are formalized and operationalized across methodological traditions. through structured tables and comparative summaries, i map core assumptions, tasks, and analytical choices from multiple causal frameworks, highlighting their connections and differences. the synthesis provides practical guidance for researchers designing causal studies, especially in settings where observational or experimental constraints challenge standard approaches. this guide spans all phases of causal analysis, including question formulation, formalization of background knowledge, selection of appropriate frameworks, choice of study design or algorithm, and interpretation. it is intended as a tool to support rigorous causal reasoning across diverse empirical domains.
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arxiv:2504.11035
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it is known that a minimal teaching set of any threshold function on the twodimensional rectangular grid consists of 3 or 4 points. we derive exact formulae for the numbers of functions corresponding to these values and further refine them in the case of a minimal teaching set of size 3. we also prove that the average cardinality of the minimal teaching sets of threshold functions is asymptotically 7 / 2. we further present corollaries of these results concerning some special arrangements of lines in the plane.
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arxiv:1307.1058
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computational acceleration of performance - metric - based materials discovery via high - throughput screening and machine learning methods is becoming widespread. nevertheless, development and optimization of the opto - electronic properties that depend on dilute concentrations of point defects in new materials have not significantly benefited from these advances. here, we present an informatics and simulation suite to computationally accelerate these processes. this will enable faster and more fundamental materials research, and reduce the cost and time associated with the materials development cycle. analogous to the new avenues enabled by current first - principles - based property databases, this type of framework will open entire new research frontiers as it proliferates.
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arxiv:1906.02776
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a boolean function $ f : \ { 0, 1 \ } ^ n \ rightarrow \ { 0, 1 \ } $ is called a dictator if it depends on exactly one variable i. e $ f ( x _ 1, x _ 2, \ ldots, x _ n ) = x _ i $ for some $ i \ in [ n ] $. in this work, we study a $ k $ - query dictatorship test. dictatorship tests are central in proving many hardness results for constraint satisfaction problems. the dictatorship test is said to have { \ em perfect completeness } if it accepts any dictator function. the { \ em soundness } of a test is the maximum probability with which it accepts any function far from a dictator. our main result is a $ k $ - query dictatorship test with perfect completeness and soundness $ \ frac { 2k + 1 } { 2 ^ k } $, where $ k $ is of the form $ 2 ^ t - 1 $ for any integer $ t > 2 $. this improves upon the result of \ cite { ty15 } which gave a dictatorship test with soundness $ \ frac { 2k + 3 } { 2 ^ k } $.
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arxiv:1702.04748
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we offer a unified approach to several phenomena related to the electromagnetic vacuum of a complex medium made of point electric dipoles. to this aim, we apply the linear response theory to the computation of the polarization field propagator and study the spectrum of vacuum fluctuations. the physical distinction among the local density of states which enter the spectra of light propagation, total dipole emission, coherent emission, total vacuum energy and schwinger - bulk energy is made clear. analytical expressions for the spectrum of dipole emission and for the vacuum energy are derived. their respective relations with the spectrum of external light and with the schwinger - bulk energy are found. the light spectrum and the schwinger - bulk energy are determined by the dyson propagator. the emission spectrum and the total vacuum energy are determined by the polarization propagator. an exact relationship of proportionality between both propagators is found in terms of local field factors. a study of the nature of stimulated emission from a single dipole is carried out. regarding coherent emission, it contains two components. a direct one which is transferred radiatively and directly from the emitter into the medium and whose spectrum is that of external light. and an indirect one which is radiated by induced dipoles. the induction is mediated by one ( and only one ) local field factor. regarding the vacuum energy, we find that in addition to the schwinger - bulk energy the vacuum energy of an effective medium contains local field contributions proportional to the resonant frequency and to the spectral line - width.
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arxiv:1002.4024
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recent advancements in machine learning have fueled research on multimodal tasks, such as for instance text - to - video and text - to - audio retrieval. these tasks require models to understand the semantic content of video and audio data, including objects, and characters. the models also need to learn spatial arrangements and temporal relationships. in this work, we analyse the temporal ordering of sounds, which is an understudied problem in the context of text - to - audio retrieval. in particular, we dissect the temporal understanding capabilities of a state - of - the - art model for text - to - audio retrieval on the audiocaps and clotho datasets. additionally, we introduce a synthetic text - audio dataset that provides a controlled setting for evaluating temporal capabilities of recent models. lastly, we present a loss function that encourages text - audio models to focus on the temporal ordering of events. code and data are available at https : / / www. robots. ox. ac. uk / ~ vgg / research / audio - retrieval / dtu /.
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arxiv:2409.00851
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recently it has been proposed that the physical spectrum of a vector - like gauge field theory may exhibit an enhanced global symmetry near a chiral / conformal phase transition. the new symmetry is related to the possibility, supported by various investigations, that a parity - doubled spectrum develops as the number of fermions nf is increased to a critical value above which it is expected that the symmetric phase is restored. we show that parity - doubling together with the associated enhanced global symmetry severely constrains the epsilon terms of the effective lagrangian involving goldstone bosons as well as massive spin - 1 particles. we extend our analysis to underlying fermions in pseudo - real representations of the gauge group.
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arxiv:hep-ph/0001303
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tools of quantum information theory offer a new perspective to characterize phases and phase transitions in interacting many - body quantum systems. the hubbard model is the archetypal model of such systems and can explain rich phenomena of quantum matter with minimal assumptions. recent measurements of entanglement - related properties of this model using ultracold atoms in optical lattices hint that entanglement could provide the key to understanding open questions of the doped hubbard model, including the remarkable properties of the pseudogap phase. these experimental findings call for a theoretical framework and new predictions. here we approach the doped hubbard model in two dimensions from the perspective of quantum information theory. we study the local entropy and the total mutual information across the doping - driven mott transition within plaquette cellular dynamical mean - field theory. we find that upon varying doping these two entanglement - related properties detect the mott insulating phase, the strongly correlated pseudogap phase, and the metallic phase. imprinted in the entanglement - related properties we also find the pseudogap to correlated metal first - order transition, its finite temperature critical endpoint, and its supercritical crossovers. through this footprint we reveal an unexpected interplay of quantum and classical correlations. our work shows that sharp variation in the entanglement - related properties and not broken symmetry phases characterizes the onset of the pseudogap phase at finite temperature.
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arxiv:2007.00562
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density inhomogeneities are ubiquitous in space and astrophysical plasmas, in particular at contact boundaries between different media. they often correspond to regions that exhibits strong dynamics on a wide range of spatial and temporal scales. indeed, density inhomogeneities are a source of free energy that can drive various instabilities such as, for instance, the lower - hybrid - drift instability which in turn transfers energy to the particles through wave - particle interactions and eventually heat the plasma. we aim at quantifying the efficiency of the lower - hybrid - drift instability to accelerate and / or heat electrons parallel to the ambient magnetic field. we combine two complementary methods : full - kinetic and quasilinear models. we report self - consistent evidence of electron acceleration driven by the development of the lower - hybrid - drift instability using 3d - 3v full - kinetic numerical simulations. the efficiency of the observed acceleration cannot be explained by standard quasilinear theory. for this reason, we develop an extended quasilinear model able to quantitatively predict the interaction between lower - hybrid fluctuations and electrons on long time scales, now in agreement with full - kinetic simulations results. finally, we apply this new, extended quasilinear model to a specific inhomogeneous space plasma boundary : the magnetopause of mercury, and we discuss our quantitative predictions of electron acceleration in support to future bepicolombo observations.
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arxiv:2104.05011
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few - shot image classification ( fsic ), which requires a model to recognize new categories via learning from few images of these categories, has attracted lots of attention. recently, meta - learning based methods have been shown as a promising direction for fsic. commonly, they train a meta - learner ( meta - learning model ) to learn easy fine - tuning weight, and when solving an fsic task, the meta - learner efficiently fine - tunes itself to a task - specific model by updating itself on few images of the task. in this paper, we propose a novel meta - learning based layer - wise adaptive updating ( lwau ) method for fsic. lwau is inspired by an interesting finding that compared with common deep models, the meta - learner pays much more attention to update its top layer when learning from few images. according to this finding, we assume that the meta - learner may greatly prefer updating its top layer to updating its bottom layers for better fsic performance. therefore, in lwau, the meta - learner is trained to learn not only the easy fine - tuning model but also its favorite layer - wise adaptive updating rule to improve its learning efficiency. extensive experiments show that with the layer - wise adaptive updating rule, the proposed lwau : 1 ) outperforms existing few - shot classification methods with a clear margin ; 2 ) learns from few images more efficiently by at least 5 times than existing meta - learners when solving fsic.
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arxiv:2007.08129
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by distributing the training process, local approximation reduces the cost of the standard gaussian process. an ensemble technique combines local predictions from gaussian experts trained on different partitions of the data. ensemble methods aggregate models ' predictions by assuming a perfect diversity of local predictors. although it keeps the aggregation tractable, this assumption is often violated in practice. even though ensemble methods provide consistent results by assuming dependencies between experts, they have a high computational cost, which is cubic in the number of experts involved. by implementing an expert selection strategy, the final aggregation step uses fewer experts and is more efficient. however, a selection approach that assigns a fixed set of experts to each new data point cannot encode the specific properties of each unique data point. this paper proposes a flexible expert selection approach based on the characteristics of entry data points. to this end, we investigate the selection task as a multi - label classification problem where the experts define labels, and each entry point is assigned to some experts. the proposed solution ' s prediction quality, efficiency, and asymptotic properties are discussed in detail. we demonstrate the efficacy of our method through extensive numerical experiments using synthetic and real - world data sets.
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arxiv:2211.09940
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we present here amusing \ textrm { + + } ; the largest compilation of nearby galaxies observed with the muse integral field spectrograph so far. this collection consists of 635 galaxies from different muse projects covering the redshift interval $ 0. 0002 < z < 0. 1 $. the sample and its main properties are characterized and described in here. it includes galaxies of almost all morphological types, with a good coverage in the color - magnitude diagram, within the stellar mass range between 10 $ ^ 8 $ to 10 $ ^ { 12 } $ m $ _ \ odot $, and with properties resembling those of a diameter - selected sample. the amusing + + sample is therefore suitable to study, with unprecendent detail, the properties of nearby galaxies at global and local scales, providing us with more than 50 million individual spectra. we use this compilation to investigate the presence of galactic outflows. we exploit the use of combined emission - line images to explore the shape of the different ionized components and the distribution along classical diagnostic diagrams to disentangle the different ionizing sources across the optical extension of each galaxy. we use the cross correlation function to estimate the level of symmetry of the emission lines as an indication of the presence of shocks and / or active galactic nuclei. we uncovered a total of 54 outflows, comprising $ \ sim $ 8 \ % of the sample. a large number of the discovered outflows correspond to those driven by active galactic nuclei ( $ \ sim $ 60 \ % ), suggesting some bias in the selection of our sample. no clear evidence was found that outflow host galaxies are highly star - forming, and outflows appear to be found within all galaxies around the star formation sequence.
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arxiv:2002.09328
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wiesner ' s unforgeable quantum money scheme is widely celebrated as the first quantum information application. based on the no - cloning property of quantum mechanics, this scheme allows for the creation of credit cards used in authenticated transactions offering security guarantees impossible to achieve by classical means. however, despite its central role in quantum cryptography, its experimental implementation has remained elusive because of the lack of quantum memories and of practical verification techniques. here, we experimentally implement a quantum money protocol relying on classical verification that rigorously satisfies the security condition for unforgeability. our system exploits polarization encoding of weak coherent states of light and operates under conditions that ensure compatibility with state - of - the - art quantum memories. we derive working regimes for our system using a security analysis taking into account all practical imperfections. our results constitute a major step towards a real - world realization of this milestone protocol.
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arxiv:1705.01428
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the exchange charge density operators that correspond to the fermi - invariant decomposition of quark - quark interactions have been constructed. their effect on the electromagnetic charge radii of the nucleons, in combination with that of the relativistic corrections to the single - quark operator, has been studied with a constituent quark model with a spin and flavor dependent hyperfine and a linear confining interaction, which gives a quantitative description of the spectra for the light and strange baryons. the model gives proton and neutron charge radii in approximate agreement with the empirical results assuming reasonable values for the radii of the constituent quarks.
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arxiv:hep-ph/9711252
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to understand changes in physical systems and facilitate decisions, explaining how model predictions are made is crucial. we use model - based interpretability, where models of physical systems are constructed by composing basic constructs that explain locally how energy is exchanged and transformed. we use the port hamiltonian ( p - h ) formalism to describe the basic constructs that contain physically interpretable processes commonly found in the behavior of physical systems. we describe how we can build models out of the p - h constructs and how we can train them. in addition we show how we can impose physical properties such as dissipativity that ensure numerical stability of the training process. we give examples on how to build and train models for describing the behavior of two physical systems : the inverted pendulum and swarm dynamics.
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arxiv:2003.10025
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in constant - roll inflation, the scalar field that drives the accelerated expansion of the universe is rolling down its potential at a constant rate. within this framework, we highlight the relations between the hubble slow - roll parameters and the potential ones, studying in detail the case of a single - field coleman - weinberg model characterised by a non - minimal coupling of the inflaton to gravity. with respect to the exact constant - roll predictions, we find that assuming an approximate slow - roll behaviour yields a difference of $ \ delta r = 0. 001 $ in the tensor - to - scalar ratio prediction. such a discrepancy is in principle testable by future satellite missions. as for the scalar spectral index $ n _ s $, we find that the existing 2 - $ \ sigma $ bound constrains the value of the non - minimal coupling to $ \ xi _ \ phi \ sim 0. 29 - 0. 31 $ in the model under consideration.
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arxiv:1711.09861
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starting from the $ 0 ^ { + + } $ glueball mass and wave function computed from lattice qcd, we compute the local potential between two constituent gluons. since the properties of constituent gluons are still a matter of research, we allow for them to be either massless, or massive with a mass around 0. 7 gev. both pictures are actually used in the literature. when the gluons are massless, the corresponding local potential is shown to be compatible with a cornell form, that is a linear confinement plus a short - range coulomb part, with standard values for the flux tube energy density and for the strong coupling constant. when the gluons are massive, the confining potential is a saturating one, commonly used to simulate string - breaking effects. these results fill a gap between lattice qcd and phenomenological models : the picture of the scalar glueball as a bound state of two constituent gluons interacting via a phenomenological potential is shown to emerge from pure gauge lattice qcd computations. moreover, we show that the allowed potential shape is constrained by the mass of the constituent gluons.
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arxiv:hep-ph/0611216
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we get a new inequality on the hodge number $ h ^ { 1, 1 } ( s ) $ of fibred algebraic complex surfaces $ s $, which is a generalization of an inequality of beauville. our inequality implies the arakelov type inequalities due to arakelov, faltings, viehweg and zuo, respectively.
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arxiv:1303.2749
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we consider c2 hamiltonian functions on compact 4 - dimensional symplectic manifolds to study elliptic dynamics of the hamiltonian flow, namely the so - called newhouse dichotomy. we show that for any open set u intersecting a far from anosov regular energy surface, there is a nearby hamiltonian having an elliptic closed orbit through u. moreover, this implies that for far from anosov regular energy surfaces of a c2 - generic hamiltonian the elliptic closed orbits are generic.
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arxiv:0801.3072
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we develop a new structure of the green ' s function of a second - order elliptic operator in divergence form in a 2d bounded domain. based on this structure and the theory of rearrangement of functions, we construct concentrated traveling - rotating helical vortex patches to 3d incompressible euler equations in an infinite pipe. by solving an equation for vorticity \ begin { equation * } w = \ frac { 1 } { \ varepsilon ^ 2 } f _ \ varepsilon \ left ( \ mathcal { g } _ { k _ h } w - \ frac { \ alpha } { 2 } | x | ^ 2 | \ ln \ varepsilon | \ right ) \ \ \ text { in } \ \ omega \ end { equation * } for small $ \ varepsilon > 0 $ and considering a certain maximization problem for the vorticity, where $ \ mathcal { g } _ { k _ h } $ is the inverse of an elliptic operator $ \ mathcal { l } _ { k _ h } $ in divergence form, we get the existence of a family of concentrated helical vortex patches, which tend asymptotically to a singular helical vortex filament evolved by the binormal curvature flow. we also get nonlinear orbital stability of the maximizers in the variational problem under $ l ^ p $ perturbation when $ p \ geq 2. $
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arxiv:2209.12237
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we derive the interaction of fermions with a dynamical space - time based on the postulate that the description of physics should be independent of the reference frame, which means to require the form - invariance of the fermion action under diffeomorphisms. the derivation is worked out in the hamiltonian formalism as a canonical transformation along the line of non - abelian gauge theories. this yields a closed set of field equations for fermions, unambiguously fixing their coupling to dynamical space - time. we encounter, in addition to the well - known minimal coupling, anomalous couplings to curvature and torsion. in torsion - free geometries that anomalous interaction reduces to a pauli - type coupling with the curvature scalar via a spontaneously emerged new coupling constant with the dimension of mass resp. \ inverse length. a consistent model hamiltonian for the free gravitational field and the impact of its functional form on the structure of the dynamical geometry space - time is discussed.
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arxiv:2101.04467
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deep distance metric learning ( ddml ), which is proposed to learn image similarity metrics in an end - to - end manner based on the convolution neural network, has achieved encouraging results in many computer vision tasks. $ l2 $ - normalization in the embedding space has been used to improve the performance of several ddml methods. however, the commonly used euclidean distance is no longer an accurate metric for $ l2 $ - normalized embedding space, i. e., a hyper - sphere. another challenge of current ddml methods is that their loss functions are usually based on rigid data formats, such as the triplet tuple. thus, an extra process is needed to prepare data in specific formats. in addition, their losses are obtained from a limited number of samples, which leads to a lack of the global view of the embedding space. in this paper, we replace the euclidean distance with the cosine similarity to better utilize the $ l2 $ - normalization, which is able to attenuate the curse of dimensionality. more specifically, a novel loss function based on the von mises - fisher distribution is proposed to learn a compact hyper - spherical embedding space. moreover, a new efficient learning algorithm is developed to better capture the global structure of the embedding space. experiments for both classification and retrieval tasks on several standard datasets show that our method achieves state - of - the - art performance with a simpler training procedure. furthermore, we demonstrate that, even with a small number of convolutional layers, our model can still obtain significantly better classification performance than the widely used softmax loss.
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arxiv:1802.09662
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recent experimental measurements, without any theoretical guidance, showed that isotropic polarization response can be achieved by increasing the number of qd layers in a qd stack. here we analyse the polarization response of multi - layer quantum dot stacks containing up to nine quantum dot layers by linearly polarized pl measurements and by carrying out a systematic set of multi - million atom simulations. the atomistic modeling and simulations allow us to include correct symmetry properties in the calculations of the optical spectra : a factor critical to explain the experimental evidence. the values of the degree of polarization ( dop ) calculated from our model follows the trends of the experimental data. we also present detailed physical insight by examining strain profiles, band edges diagrams and wave function plots. multi - directional pl measurements and calculations of the dop reveal a unique property of inas quantum dot stacks that the te response is anisotropic in the plane of the stacks. therefore a single value of the dop is not sufficient to fully characterize the polarization response. we explain this anisotropy of the te - modes by orientation of hole wave functions along the [ - 110 ] direction. our results provide a new insight that isotropic polarization response measured in the experimental pl spectra is due to two factors : ( i ) tm [ 001 ] - mode contributions increase due to enhanced intermixing of hh and lh bands, and ( ii ) te [ 110 ] - mode contributions reduce significantly due to hole wave function alignment along the [ - 110 ] direction. we also present optical spectra for various geometry configurations of quantum dot stacks to provide a guide to experimentalists for the design of multi - layer qd stacks for optical devices. our results predict that the qd stacks with identical layers will exhibit lower values of the dop than the stacks with non - identical layers.
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arxiv:1106.0517
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we study inelastic ( dynamical ) impurity scattering effects in two - band superconductors with the same ( $ s _ { + + } $ wave ) or different ( $ s _ \ pm $ wave ) sign order parameters. we focus on the enhancement of the superconducting transition temperature $ t _ { \ rm c } $ by magnetic interband scattering with the interchange of crystal - field singlet ground and multiplet excited states. either the $ s _ { + + } $ - wave or $ s _ \ pm $ - wave state is favored by the impurity - mediated pairing, which depends on the magnetic and nonmagnetic scattering strengths derived from the hybridization of the impurity states with the conduction bands. the details are examined for the singlet - triplet configuration that is suggestive of pr impurities in the skutterudite superconductor laos $ _ 4 $ sb $ _ { 12 } $.
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arxiv:1007.1313
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many quantum algorithms demand a large number of repetitions to obtain reliable statistical results. thus, at each repetition it is necessary to reset the qubits efficiently and precisely in the shortest possible time, so that quantum computers actually have advantages over classical ones. in this work, we perform a detailed analysis on three different models for information resetting in superconducting qubits. our experimental setup consists of a main qubit coupled to different auxiliary dissipative systems, that are employed in order to perform the erasing of the information of the main qubit. our analysis shows that it is not enough to increase the coupling and the dissipation rate associated with the auxiliary systems to decrease the resetting time of the main qubit, a fact that motivates us to find the optimal set of parameters for each studied approach, allowing a significant decrease in the reset time of the three models analyzed.
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arxiv:2304.00684
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superqubits provide a supersymmetric generalisation of the conventional qubit in quantum information theory. after a review of their current status, we address the problem of generating entangled states. we introduce the global unitary supergroup $ \ text { uosp } ( ( 3 ^ n + 1 ) / 2 | ( 3 ^ n - 1 ) / 2 ) $ for an $ n $ - superqubit system, which contains as a subgroup the local unitary supergroup $ [ \ text { uosp } ( 2 | 1 ) ] ^ n $. while for $ 4 > n > 1 $ the bosonic subgroup in $ \ text { uosp } ( ( 3 ^ n + 1 ) / 2 | ( 3 ^ n - 1 ) / 2 ) $ does not contain the standard global unitary group $ \ text { su } ( 2 ^ n ) $, it does have an $ \ text { usp } ( 2 ^ n ) \ subset \ text { su } ( 2 ^ n ) $ subgroup which acts transitively on the $ n $ - qubit subspace, as required for consistency with the conventional multi - qubit framework. for two superqubits the $ \ text { uosp } ( 5 | 4 ) $ action is used to generate entangled states from the " bosonic " separable state $ | 00 \ rangle $.
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arxiv:1411.7311
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we study $ k $ - star decompositions, that is, partitions of the edge set into disjoint stars with $ k $ edges, in the uniformly random $ d $ - regular graph model $ \ mathcal { g } _ { n, d } $. using the small subgraph conditioning method, we prove an existence result for such decompositions for all $ d, k $ such that $ d / 2 < k \ leq d / 2 + \ max \ { 1, \ frac { 1 } { 6 } \ log d \ } $. more generally, we give a sufficient existence condition that can be checked numerically for any given values of $ d $ and $ k $. complementary negative results are obtained using the independence ratio of random regular graphs. our results establish an existence threshold for $ k $ - star decompositions in $ \ mathcal { g } _ { n, d } $ for all $ d \ leq 100 $ and $ k > d / 2 $. for smaller values of $ k $, the connection between $ k $ - star decompositions and $ \ beta $ - orientations allows us to apply results of thomassen ( 2012 ) and lov \ ' asz, thomassen, wu and zhang ( 2013 ). we prove that random $ d $ - regular graphs satisfy their assumptions with high probability, thus establishing a. a. s. existence of $ k $ - star decompositions ( i ) when $ 2k ^ 2 + k \ leq d $, and ( ii ) when $ k $ is odd and $ k < d / 2 $.
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arxiv:2308.16037
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one of the principal results obtained by the egret experiment aboard the compton gamma - ray observatory ( cgro ) was the detection of several gamma - ray bursts ( grbs ) above 100 mev. the broad - band spectra obtained for these bursts gave no indication of any high energy spectral attenuation that might preclude detection of bursts by ground - based cerenkov telescopes ( acts ), thus motivating several tev observational programs. this paper explores the expectations for the spectral properties in the tev and sub - tev bands for bursts, in particular how attenuation of photons by pair creation internal to the source modifies the spectrum to produce distinctive spectral signatures. the energy of spectral breaks and the associated spectral indices provide valuable information that can constrain the bulk lorentz factor of the grb outflow at a given time. these characteristics define palpable observational goals for act programs, and strongly impact the observability of bursts in the tev band.
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arxiv:astro-ph/9911061
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a mathematical model, suitable for smartphone implementation, is presented to simulate the performance of a rainwater harvesting system equipped with a covered storage tank. this model serves to determine the optimal tank size and develop strategies to mitigate drought conditions.
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arxiv:2404.13080
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the inclusive photoproduction of two heavy quarks, separated by a large rapidity interval, is proposed as a new channel for the manifestation of the balitsky - fadin - kuraev - lipatov ( bfkl ) dynamics. the extension to the hadroproduction case is also discussed.
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arxiv:1906.05940
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just fourteen years ago the solar system represented the only known planetary system in the galaxy, and conceptions of planet formation were shaped by this sample of one. since then, 320 planets have been discovered orbiting 276 individual stars. this large and growing ensemble of exoplanets has informed theories of planet formation, placed the solar system in a broader context, and revealed many surprises along the way. in this review i provide an overview of what has been learned from studies of the occurrence, orbits and physical structures of planets. after taking a look back at how far the field has advanced, i will discuss some of the future directions of exoplanetary science, with an eye toward the detection and characterization of earth - like planets around other stars.
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arxiv:0903.3059
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morphisms between ( formal ) contexts are certain pairs of maps, one between objects and one between attributes of the contexts in question. we study several classes of such morphisms and the connections between them. among other things, we show that the category clc of complete lattices with complete homomorphisms is ( up to a natural isomorphism ) a full reflective subcategory of the category of contexts with so - called conceptual morphisms ; the reflector associates with each context its concept lattice. on the other hand, we obtain a dual adjunction between clc and the category of contexts with so - called concept continuous morphisms. suitable restrictions of the adjoint functors yield a categorical equivalence and a duality between purified contexts and doubly based lattices, and in particular, between reduced contexts and irreducibly bigenerated complete lattices. a central role is played by continuous maps between closure spaces and by adjoint maps between complete lattices.
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arxiv:1407.0512
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automatic feature learning algorithms are at the forefront of modern day machine learning research. we present a novel algorithm, supervised q - walk, which applies q - learning to generate random walks on graphs such that the walks prove to be useful for learning node features suitable for tackling with the node classification problem. we present another novel algorithm, k - hops neighborhood based confidence values learner, which learns confidence values of labels for unlabelled nodes in the network without first learning the node embedding. these confidence values aid in learning an apt reward function for q - learning. we demonstrate the efficacy of supervised q - walk approach over existing state - of - the - art random walk based node embedding learners in solving the single / multi - label multi - class node classification problem using several real world datasets. summarising, our approach represents a novel state - of - the - art technique to learn features, for nodes in networks, tailor - made for dealing with the node classification problem.
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arxiv:1710.00978
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we study a multi - armed bandit problem in a dynamic environment where arm rewards evolve in a correlated fashion according to a markov chain. different than much of the work on related problems, in our formulation a learning algorithm does not have access to either a priori information or observations of the state of the markov chain and only observes smoothed reward feedback following time intervals we refer to as epochs. we demonstrate that existing methods such as ucb and $ \ varepsilon $ - greedy can suffer linear regret in such an environment. employing mixing - time bounds on markov chains, we develop algorithms called epochucb and epochgreedy that draw inspiration from the aforementioned methods, yet which admit sublinear regret guarantees for the problem formulation. our proposed algorithms proceed in epochs in which an arm is played repeatedly for a number of iterations that grows linearly as a function of the number of times an arm has been played in the past. we analyze these algorithms under two types of smoothed reward feedback at the end of each epoch : a reward that is the discount - average of the discounted rewards within an epoch, and a reward that is the time - average of the rewards within an epoch.
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arxiv:1803.04008
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the purpose of this paper is to study the generalized fong - - vasicek two - factor interest rate model with stochastic volatility. in this model the dispersion of the stochastic short rate ( square of volatility ) is assumed to be stochastic as well and it follows a non - negative process with volatility proportional to the square root of dispersion. the drift of the stochastic process for the dispersion is assumed to be in a rather general form including, in particular, linear function having one root ( yielding the original fong - - vasicek model or a cubic like function having three roots ( yielding a generalized fong - - vasicek model for description of the volatility clustering ). we consider averaged bond prices with respect to the limiting distribution of stochastic dispersion. the averaged bond prices depend on time and current level of the short rate like it is the case in many popular one - factor interest rate model including in particular the vasicek and cox - - ingersoll - ross model. however, as a main result of this paper we show that there is no such one - factor model yielding the same bond prices as the averaged values described above.
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arxiv:0811.0473
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the gravitational - wave signal gw150914 was first identified on sept 14 2015 by searches for short - duration gravitational - wave transients. these searches identify time - correlated transients in multiple detectors with minimal assumptions aboutthe signal morphology, allowing them to be sensitive to gravitational waves emitted by a wide range of sources including binary black - hole mergers. over the observational period from september 12th to october 20th 2015, these transient searches were sensitive to binary black - hole mergers similar to gw150914 to an average distance of $ \ sim 600 $ mpc. in this paper, we describe the analyses that first detected gw150914 as well as the parameter estimation and waveform reconstruction techniques that initially identified gw150914 as the merger of two black holes. we find that the reconstructed waveform is consistent with the signal from a binary black - hole merger with a chirp mass of $ \ sim 30 \, m _ \ odot $ and a total mass before merger of $ \ sim 70 \, m _ \ odot $ in the detector frame.
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arxiv:1602.03843
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by the tang dynasty study of mathematics was fairly standard in the great schools. the ten computational canons was a collection of ten chinese mathematical works, compiled by early tang dynasty mathematician li chunfeng ( 李 風 602 – 670 ), as the official mathematical texts for imperial examinations in mathematics. the sui dynasty and tang dynasty ran the " school of computations ". wang xiaotong was a great mathematician in the beginning of the tang dynasty, and he wrote a book : jigu suanjing ( continuation of ancient mathematics ), where numerical solutions which general cubic equations appear for the first time. the tibetans obtained their first knowledge of mathematics ( arithmetic ) from china during the reign of nam - ri srong btsan, who died in 630. the table of sines by the indian mathematician, aryabhata, were translated into the chinese mathematical book of the kaiyuan zhanjing, compiled in 718 ad during the tang dynasty. although the chinese excelled in other fields of mathematics such as solid geometry, binomial theorem, and complex algebraic formulas, early forms of trigonometry were not as widely appreciated as in the contemporary indian and islamic mathematics. yi xing, the mathematician and buddhist monk was credited for calculating the tangent table. instead, the early chinese used an empirical substitute known as chong cha, while practical use of plane trigonometry in using the sine, the tangent, and the secant were known. yi xing was famed for his genius, and was known to have calculated the number of possible positions on a go board game ( though without a symbol for zero he had difficulties expressing the number ). = = song and yuan dynasties = = northern song dynasty mathematician jia xian developed an additive multiplicative method for extraction of square root and cubic root which implemented the " horner " rule. four outstanding mathematicians arose during the song dynasty and yuan dynasty, particularly in the twelfth and thirteenth centuries : yang hui, qin jiushao, li zhi ( li ye ), and zhu shijie. yang hui, qin jiushao, zhu shijie all used the horner - ruffini method six hundred years earlier to solve certain types of simultaneous equations, roots, quadratic, cubic, and quartic equations. yang hui was also the first person in history to discover and prove " pascal ' s triangle ", along with its binomial proof ( although the earliest mention of the pascal ' s triangle in china exists before the eleventh century ad ). li zhi on the
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https://en.wikipedia.org/wiki/Chinese_mathematics
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slac energy doubler ( sled ) type radio - frequency pulse compressors are widely used in large - scale particle accelerators for converting long - duration moderate - power input pulse into short - duration high - power output pulse. the phase shift keying ( psk ) is one of the key components in sled pulse compression systems. performance of the psk will influence the output characteristics of sled, such as rise - time of the output pulse, the maximal peak power gain, and the energy efficiency. in this paper, high power microwave source based on power combining and pulse compression of conventional klystrons was introduced, the nonideal psk with slow switching speed and without power output during the switching process were investigated, the experimental results with nonideal psk agreed well with the analytical results.
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arxiv:1504.01449
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uncertainty quantification is a critical aspect of machine learning models, providing important insights into the reliability of predictions and aiding the decision - making process in real - world applications. this paper proposes a novel way to use variance - based measures to quantify uncertainty on the basis of second - order distributions in classification problems. a distinctive feature of the measures is the ability to reason about uncertainties on a class - based level, which is useful in situations where nuanced decision - making is required. recalling some properties from the literature, we highlight that the variance - based measures satisfy important ( axiomatic ) properties. in addition to this axiomatic approach, we present empirical results showing the measures to be effective and competitive to commonly used entropy - based measures.
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arxiv:2401.00276
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in hyperbolic dynamics, a well - known result is that every hyperbolic attracting set, have a finite pseudo - orbit tracing property ( fpotp ). it ' s natural to wonder if this result is maintained in the sectional - hyperbolic dynamics ; komuro in [ lorenz attractors do not have the pseudo - orbit tracing property ], provides a negative answer for this question, by proving that the geometric lorenz attractor doesn ' t have a fpotp. in this paper, we generalized the result of komuro, we prove that every codimension one sectional - hyperbolic attractor set with a unique singularity lorenz - like, which is of boundary - type, does not have fpotp.
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arxiv:2006.14369
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the production of the standard model ( sm ) higgs boson ( h ) in association with a jet is compared with that of the lightest scalar higgs boson ( h ^ 0 ) and the pseudoscalar higgs boson ( a ^ 0 ) of the minimal supersymmetric model ( mssm ) at both the cern large hadron collider ( lhc ) and the fermilab tevatron. we include both top and bottom quark loops to lowest order in qcd and investigate the limits of zero quark mass and infinite quark mass.
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arxiv:hep-ph/0311199
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we present detailed analytical calculations for an 1d ising ring of arbitrary number of spin - 1 / 2 particles, in order to reveal entanglement properties of the stationary states. we show that the ground state and specific eigenstates of the ising hamiltonian posses remarkable entanglement properties that can reveal new insight into quantum correlations present in the ising model. this correlations might be exploited in quantum information processing. we propose an intuitive picture of the behaviour of multipartite entanglement and discuss a relation of our results to some aspects of phase transitions in the ising model.
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arxiv:quant-ph/0312154
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we compute nuclear force in a holographic model of qcd on the basis of a d4 - d8 brane configuration in type iia string theory. repulsive core of nucleons is quite important in nuclear physics, but its origin has not been well - understood in strongly - coupled qcd. we find that string theory via gauge / string duality deduces this repulsive core at short distance between nucleons. since baryons in the model are realized as solitons given by yang - mills instanton configuration on flavor d8 - branes, adhm construction of two instantons probes well the nucleon interaction at short scale, which provides the nuclear force quantitatively. we obtain, as well as a tensor force, a central force which is strongly repulsive as suggested in experiments and lattice results. in particular, the nucleon - nucleon potential v ( r ) ( as a function of the distance ) scales as 1 / r ^ 2, which is peculiar to the holographic model. we compare our results with one - boson exchange model using the nucleon - nucleon - meson coupling obtained in our previous paper ( arxiv : 0806. 3122 ).
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arxiv:0901.4449
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we demonstrate that in a recently proposed unified leptoquark model based on the gauge group $ su ( 4 ) _ c \ times su ( 2 ) _ l \ times u ( 1 ) _ r $ significant deviations from the standard model values of $ r _ k $ and $ r _ { k ^ * } $ can be accommodated without any need of extra heavy fermions. low energy data, in particular lepton flavour violating $ \ mu $ decays and $ k _ l \ to e \ mu $, severely constrain the available parameter space. we show that in the allowed part of the parameter space ( i ) some of the lepton - flavour - violating tau decay branching ratios are predicted to be close to their current experimental limits. ( ii ) the underlying scalar leptoquarks can be probed at the lhc via their dominant decay modes into tau - leptons and electrons and the third generation quarks. ( iii ) the constraints from meson oscillations imply that the masses of scalar gluons, another pair of coloured multiplets around, have to be bigger than around 15 tev and, thus, they can be probed only at a future 100 tev collider. in both neutral and charged variants, these scalars decay predominantly into third generation quarks, with up to $ o $ ( 10 \ % ) branching ratios into family - mixed final states. besides that, we comment on the phenomenology of the scalar gluons in the current scenarios in the case that the $ b $ - decay anomalies eventually disappear.
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arxiv:1812.07592
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a mathematical method for constructing fractal curves and surfaces, termed the $ p \ lambda n $ fractal decomposition, is presented. it allows any function to be split into a finite set of fractal discontinuous functions whose sum is equal everywhere to the original function. thus, the method is specially suited for constructing families of fractal objects arising from a conserved physical quantity, the decomposition yielding an exact partition of the quantity in question. most prominent classes of examples are provided by hamiltonians and partition functions of statistical ensembles : by using this method, any such function can be decomposed in the ordinary sum of a specified number of terms ( generally fractal functions ), the decomposition being both exact and valid everywhere on the domain of the function.
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arxiv:1505.02547
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we study generic einstein - maxwell - kalb - ramond - dilaton actions, and derive conditions under which they give rise to static, spherically symmetric black hole solutions. we obtain new asymptotically flat and non - flat black hole solutions which are in general electrically and magnetically charged. they have positive definite and finite quasi - local masses. existing non - rotating black hole solutions ( including those appearing in low energy string theory ) are recovered in special limits.
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arxiv:hep-th/0508150
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in this paper, we introduce quantile coherency to measure general dependence structures emerging in the joint distribution in the frequency domain and argue that this type of dependence is natural for economic time series but remains invisible when only the traditional analysis is employed. we define estimators which capture the general dependence structure, provide a detailed analysis of their asymptotic properties and discuss how to conduct inference for a general class of possibly nonlinear processes. in an empirical illustration we examine the dependence of bivariate stock market returns and shed new light on measurement of tail risk in financial markets. we also provide a modelling exercise to illustrate how applied researchers can benefit from using quantile coherency when assessing time series models.
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arxiv:1510.06946
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modifications to improve its reliability and safety. following the collapse of the soviet union, the russian federation and united states initiated the shuttle - mir program. the first russian cosmonaut flew on the sts - 60 mission in 1994 and the discovery rendezvoused, but did not dock with, the russian mir in the sts - 63 mission. this was followed by atlantis ' sts - 71 mission where it accomplished the initial intended mission for the space shuttle, docking with a space station and transferring supplies and personnel. the shuttle - mir program would continue until 1998, when a series of orbital accidents on the space station spelled an end to the program. in 2003, a second space shuttle was destroyed when the columbia was destroyed upon reentry during the sts - 107 mission, resulting in the loss of the spacecraft and all seven astronauts. this accident marked the beginning of the retiring of the space shuttle program, with president george w. bush directing that upon the completion of the international space station, the space shuttle be retired. in 2006, the space shuttle returned to flight, conducting several mission to service the hubble space telescope, but was retired following the sts - 135 resupply mission to the international space station in 2011. = = = space stations = = = nasa never gave up on the idea of a space station after skylab ' s reentry in 1979. the agency began lobbying politicians to support building a larger space station as soon as the space shuttle began flying, selling it as an orbital laboratory, repair station, and a jumping off point for lunar and mars missions. nasa found a strong advocate in president ronald reagan, who declared in a 1984 speech : america has always been greatest when we dared to be great. we can reach for greatness again. we can follow our dreams to distant stars, living and working in space for peaceful, economic, and scientific gain. tonight i am directing nasa to develop a permanently manned space station and to do it within a decade. in 1985, nasa proposed the space station freedom, which both the agency and president reagan intended to be an international program. while this would add legitimacy to the program, there were concerns within nasa that the international component would dilute its authority within the project, having never been willing to work with domestic or international partners as true equals. there was also a concern with sharing sensitive space technologies with the europeans, which had the potential to dilute america ' s technical lead. ultimately, an international agreement to develop the space station freedom program would be signed with thirteen countries in 1985, including the european space agency
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https://en.wikipedia.org/wiki/NASA
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high - resolution infrared spectroscopy in the 2. 3 - 4. 6 micron region is reported for the peculiar a supergiant, single - lined spectroscopic binary hr 4049. lines from the co fundamental and first overtone, oh fundamental, and several h2o vibration - rotation transitions have been observed in the near - infrared spectrum. the spectrum of hr 4049 appears principally in emission through the 3 and 4. 6 micron region and in absorption in the 2 micron region. the 4. 6 micron spectrum shows a rich ' forest ' of emission lines. all the spectral lines observed in the 2. 3 - 4. 6 micron spectrum are shown to be circumbinary in origin. the presence of oh and h2o lines confirm the oxygen - rich nature of the circumbinary gas which is in contrast to the previously detected carbon - rich material. the emission and absorption line profiles show that the circumbinary gas is located in a thin, rotating layer near the dust disk. the properties of the dust and gas circumbinary disk and the spectroscopic orbit yield masses for the individual stars, m _ ai ~ 0. 58 msolar and m _ mv ~ 0. 34 msolar. gas in the disk also has an outward flow with a velocity of $ \ gtrsim $ 1 km / s. the severe depletion of refractory elements but near - solar abundances of volatile elements observed in hr 4049 results from abundance winnowing. the separation of the volatiles from the grains in the disk and the subsequent accretion by the star are discussed. contrary to prior reports, the hr 4049 carbon and oxygen isotopic abundances are typical agb values : 12c / 13c = 6 ^ { + 9 } _ { - 4 } and 16o / 17o > 200.
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arxiv:0704.1237
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in this work, we develop a fast hierarchical solver for solving large, sparse least squares problems. we build upon the algorithm, spaqr ( sparsified qr ), that was developed by the authors to solve large sparse linear systems. our algorithm is built on top of a nested dissection based multifrontal qr approach. we use low - rank approximations on the frontal matrices to sparsify the vertex separators at every level in the elimination tree. using a two - step sparsification scheme, we reduce the number of columns and maintain the ratio of rows to columns in each front without introducing any additional fill - in. with this improvised scheme, we show that the runtime of the algorithm scales as $ \ mathcal { o } ( m \ log n ) $ and uses $ \ mathcal { o } ( m ) $ memory to store the factorization. this is achieved at the expense of a small and controllable approximation error. the end result is an approximate factorization of the matrix stored as a sequence of sparse orthogonal and upper - triangular factors and hence easy to apply / solve with a vector. finally, we compare the performance of the spaqr algorithm in solving sparse least squares problems with direct multifrontal qr and cgls iterative method with a standard diagonal preconditioner.
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arxiv:2102.09878
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in mathematics, an element ( or member ) of a set is any one of the distinct objects that belong to that set. for example, given a set called a containing the first four positive integers ( a = { 1, 2, 3, 4 } { \ displaystyle a = \ { 1, 2, 3, 4 \ } } ), one could say that " 3 is an element of a ", expressed notationally as 3 ∈ a { \ displaystyle 3 \ in a }. = = sets = = writing a = { 1, 2, 3, 4 } { \ displaystyle a = \ { 1, 2, 3, 4 \ } } means that the elements of the set a are the numbers 1, 2, 3 and 4. sets of elements of a, for example { 1, 2 } { \ displaystyle \ { 1, 2 \ } }, are subsets of a. sets can themselves be elements. for example, consider the set b = { 1, 2, { 3, 4 } } { \ displaystyle b = \ { 1, 2, \ { 3, 4 \ } \ } }. the elements of b are not 1, 2, 3, and 4. rather, there are only three elements of b, namely the numbers 1 and 2, and the set { 3, 4 } { \ displaystyle \ { 3, 4 \ } }. the elements of a set can be anything. for example the elements of the set c = { r e d, 12, b } { \ displaystyle c = \ { \ mathrm { \ color { red } red }, \ mathrm { 12 }, b \ } } are the color red, the number 12, and the set b. in logical terms, ( x ∈ y ) ↔ x [ p x = y ] : x ∈ d y { \ displaystyle ( x \ in y ) \ leftrightarrow \ forall x [ p _ { x } = y ] : x \ in { \ mathfrak { d } } y }. = = notation and terminology = = the binary relation " is an element of ", also called set membership, is denoted by the symbol " ∈ ". writing x ∈ a { \ displaystyle x \ in a } means that " x is an element of a ". equivalent expressions are " x is a member of a ", " x belongs to a ", " x is in a " and " x lies in
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https://en.wikipedia.org/wiki/Element_(mathematics)
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using mesoscopic numerical simulations and analytical theory we investigate the coarsening of the solvent structure around a colloidal particle emerging after a temperature quench of the colloid surface. qualitative differences in the coarsening mechanisms are found, depending on the composition of the binary liquid mixture forming the solvent and on the adsorption preferences of the colloid. for an adsorptionwise neutral colloid, as function of time the phase being next to its surface alternates. this behavior sets in on the scale of the relaxation time of the solvent and is absent for colloids with strong adsorption preferences. a janus colloid, with a small temperature difference between its two hemispheres, reveals an asymmetric structure formation and surface enrichment around it, even if the solvent is within its one - phase region and if the temperature of the colloid is above the critical demixing temperature $ t _ c $ of the solvent. our phenomenological model turns out to capture recent experimental findings according to which, upon laser illumination of a janus colloid and due to the ensuing temperature gradient between its two hemispheres, the surrounding binary liquid mixture develops a concentration gradient.
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arxiv:1712.08063
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performing light scattering experiments we show that introducing short - ranged attraction to a colloidal suspension of nearly hard spheres by addition of free polymer produces new glass transition phenomena. we observe a dramatic acceleration of the density fluctuations amounting to the melting of a colloidal glass. increasing the strength of the attractions the system freezes into another nonergodic state sharing some qualitative features with gel states occurring at lower colloid packing fractions. this reentrant glass transition is in qualitative agreement with recent theoretical predictions.
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arxiv:cond-mat/0203513
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measuring instruments are vital for obtaining accurate data in various fields, including scientific research, engineering, and manufacturing. however, data acquisition can be challenging, particularly when direct cable connections are not feasible or difficult to establish. in this paper, we propose a novel method for measuring instrument data acquisition utilizing a camera to capture the instrument display and image processing techniques to extract the measured values. our method combines computer vision and machine learning techniques to recognize and extract numerical values from the instrument display. we demonstrate the effectiveness and accuracy of this approach by applying it to capture the magnetic field of a permanent magnet using a gauss meter and webcam. our results indicate that the proposed method offers a practical and accurate solution for data acquisition in cases where direct cable connections are not possible. this method has potential applications in scientific research, engineering, and manufacturing industries.
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arxiv:2302.07091
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several experiments have been performed to investigate the mechanical vibrations associated with trachea and larynx when italian vowels are emitted. the mechanical measurements have been made by using two laser doppler vibrometers ( based on the well - known not - invasive optical measurement technique ) coupled with the acoustic field measured by high - quality certified microphones. the recorded signals are analyzed by using well - established methods in time and frequency domains. the signals of the mechanical vibrations along the trachea and the larynx are compared with those of the acoustic ones. focusing the attention of the signals ' onsets, we can observe an upward propagation of the mechanical vibrations for which it is possible to estimate a delay between the traces. we observe that the mechanical oscillations at the trachea start before the larynx and acoustic oscillations. moreover these tracheal oscillations are self - oscillations in time and are associated with the pitch production, indicating a further hydrodynamic instability at trachea. this leads to new insights in the mechanism controlling the pitch in the speech.
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arxiv:1311.5544
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in this work, we experimentally demonstrate two - state fluctuations in a metal - insulator - semiconductor ( mis ) device formed out of a metallic atomic force microscopy tip, vacuum gap, and multilayer mose $ _ 2 $ sample. we show that noise in this device is intrinsically bias - dependent due to the bias - dependent surface potential, and does not require that the frequency or magnitude of individual dopant fluctuations are themselves bias - dependent. finally, we measure spatial nonhomogeneities in band bending ( charge reorganization ) timescales.
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arxiv:2109.15275
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we study the connection between lagrangian and hamiltonian descriptions of closed / open dynamics, for a collection of particles with quadratic interaction ( closed system ) and a sub - collection of particles with linear damping ( open system ). we consider both continuous and discrete versions of mechanics. we define the damping reduction as the mapping from the equations of motion of the closed system to those of the open one. as variational instruments for the obtention of these equations we use the hamilton ' s principle ( closed dynamics ) and lagrange - d ' alembert principle ( open dynamics ). we establish the commutativity of the branches legendre transform + damping reduction and damping reduction + legendre transform, where the legendre transform is the usual mapping between lagrangian and hamiltonian mechanics. at a discrete level, this commutativity provides interesting insight about the resulting integrators. more concretely, discrete damping reduction yields particular numerical schemes for linearly damped systems which are not symplectic anymore, but preserve some of the features of their symplectic counterparts from which they proceed ( for instance the semi - implicitness in some cases ). the theoretical results are illustrated with the examples of the heat bath and transmission lines. in the latter case some simulations are displayed, showing a better performance of the integrators with variational origin.
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arxiv:1809.05532
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let $ ( g _ { n } ) _ { n \ geq 1 } $ be a sequence of independent and identically distributed ( i. i. d. ) $ d \ times d $ real random matrices. for $ n \ geq 1 $ set $ g _ n = g _ n \ ldots g _ 1 $. given any starting point $ x = \ mathbb r v \ in \ mathbb { p } ^ { d - 1 } $, consider the markov chain $ x _ n ^ x = \ mathbb r g _ n v $ on the projective space $ \ mathbb p ^ { d - 1 } $ and the norm cocycle $ \ sigma ( g _ n, x ) = \ log \ frac { | g _ n v | } { | v | } $, for an arbitrary norm $ | \ cdot | $ on $ \ mathbb r ^ { d } $. under suitable conditions we prove a berry - esseen type theorem and an edgeworth expansion for the couple $ ( x _ n ^ x, \ sigma ( g _ n, x ) ) $. these results are established using a brand new smoothing inequality on complex plane, the saddle point method and additional spectral gap properties of the transfer operator related to the markov chain $ x _ n ^ x $. cram \ ' { e } r type moderate deviation expansions as well as a local limit theorem with moderate deviations are proved for the couple $ ( x _ n ^ x, \ sigma ( g _ n, x ) ) $ with a target function $ \ varphi $ on the markov chain $ x _ n ^ x $.
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arxiv:1907.02438
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the study of local models using finite shared randomness originates from the consideration about the cost of classically simulating entanglement in composite quantum systems. we construct explicitly two families of local - hidden - state ( lhs ) models for t - states, by mapping the problem to the werner state. the continuous decreasing of shared randomness along with entanglement, as the anisotropy increases, can be observed in the one from the most economical model for the werner state. the construction of the one for separable states shows that the separable boundary of t - states can be generated from the one of the werner state, and the cost is 2 classical bits.
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arxiv:1903.03957
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common observations of the unpredictability of human behavior and the influence of one question on the answer to another suggest social science experiments are probabilistic and may be mutually incompatible with one another, characteristics attributed to quantum mechanics ( as distinguished from classical mechanics ). this paper examines this superficial similarity in depth using the foulis - randall operational statistics language. in contradistinction to physics, social science deals with complex, open systems for which the set of possible experiments is unknowable and outcome interference is a graded phenomenon resulting from the ways the human brain processes information. it is concluded that social science is, in some ways, " less classical " than quantum mechanics, but that generalized " quantum " structures may provide appropriate descriptions of social science experiments. specific challenges to extending " quantum " structures to social science are identified.
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arxiv:quant-ph/0307234
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we formulate the frobenius - norm - based measures for quantum coherence and asymmetry respectively. in contrast to the resource theory of coherence and asymmetry, we construct a natural measure of quantum coherence inspired from optical coherence theory while the group theoretical approach is employed to quantify the asymmetry of quantum states. besides their simple structures and explicit physical meanings, we observe that these quantities are intimately related to the purity ( or linear entropy ) of the corresponding quantum states. remarkably, we demonstrate that the proposed coherence quantifier is not only a measure of mixedness, but also an intrinsic ( basis - independent ) quantification of quantum coherence contained in quantum states, which can also be viewed as a normalized version of brukner - zeilinger invariant information. in our context, the asymmetry of n - qubit quantum systems is considered under local independent and collective su ( 2 ) transformations. intriguingly, it is illustrated that the collective effect has a significant impact on the asymmetry measure, and quantum correlation between subsystems plays a non - negligible role in this circumstance.
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arxiv:1605.00789
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the use of a wire probe is a robust method for beam profile measurement, but it can only provide a 1d projection of the beam profile. in this study, we developed a novel method for measuring a beam projected from a 360 { \ deg } angle by a dual - axis rotation of a wire probe and obtaining a complete 2d profile via image reconstruction. we conducted a proof - of - principle study using an ar + ion beam and optimized the reconstruction algorithm. the experimental results showed that the use of the order subsets expectation maximization ( os - em ) algorithm is the most reasonable method, providing a highly accurate absolute 2d beam profile within a processing time on the millisecond scale. furthermore, analysis of 2d profiles at different probing positions provided the beam direction and the phase space distribution. this versatile method can be applied to various fields of quantum beam technologies, such as particle therapy, semiconductor processing, and material analysis, as well as basic scientific research.
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arxiv:2503.13209
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the physics learning is very important to techniques teaching and the engineers upbringing. however, there is evidence that science classes from elementary school through to university are generally failing to provide most students with an understanding of physics we have explored the use of a novel aspect of information technology : interactive simulations to learning of energys concepts. this way, students can construct their understanding through semi - guided exploration. research has shown this process to be an effective and engaging way to learn.
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arxiv:1606.00245
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this note proves the existence of universal rational parametrizations. the description involves homogeneous coordinates on a toric variety coming from a lattice polytope. we first describe how smooth toric varieties lead to universal rational parametrizations of certain projective varieties. we give numerous examples and then discuss what happens in the singular case. we also describe rational maps to smooth toric varieties.
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arxiv:math/0303316
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we use the erosita final equatorial - depth survey ( efeds ) to measure the rest - frame 0. 1 - 2. 4 kev band x - ray luminosities of $ \ sim $ 600, 000 desi groups using two different algorithms in the overlap region of the two observations. these groups span a large redshift range of $ 0. 0 \ le z _ g \ le 1. 0 $ and group mass range of $ 10 ^ { 10. 76 } h ^ { - 1 } m _ { \ odot } \ le m _ h \ le 10 ^ { 15. 0 } h ^ { - 1 } m _ { \ odot } $. ( 1 ) using the blind detection pipeline of efeds, we find that 10932 x - ray emission peaks can be cross matched with our groups, $ \ sim 38 \ % $ of which have signal - to - noise ratio $ \ rm { s } / \ rm { n } \ geq 3 $ in x - ray detection. comparing to the numbers reported in previous studies, this matched sample size is a factor of $ \ sim 6 $ larger. ( 2 ) by stacking x - ray maps around groups with similar masses and redshifts, we measure the average x - ray luminosity of groups as a function of halo mass in five redshift bins. we find, in a wide halo mass range, the x - ray luminosity, $ l _ { \ rm x } $, is roughly linearly proportional to $ m _ { h } $, and is quite independent to the redshift of the groups. ( 3 ) we use a poisson distribution to model the x - ray luminosities obtained using two different algorithms and obtain best - fit $ l _ { \ rm x } = 10 ^ { 28. 46 \ pm0. 03 } m _ { h } ^ { 1. 024 \ pm0. 002 } $ and $ l _ { \ rm x } = 10 ^ { 26. 73 \ pm 0. 04 } m _ { h } ^ { 1. 140 \ pm 0. 003 } $ scaling relations, respectively. the best - fit slopes are flatter than the results previously obtained, but closer to a self - similar prediction.
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arxiv:2306.02594
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due to high - cadence automated surveys, we can now detect and classify supernovae ( sne ) within a few days after explosion, if not earlier. early - time spectra of young sne directly probe the outermost layers of the ejecta, providing insights into the extent of stripping in the progenitor star and the explosion mechanism in the case of core - collapse supernovae. however, many sne show overlapping observational characteristics at early times, complicating the early - time classification. in this paper, we focus on the study and classification of type ib supernovae ( sne ib ), which are a subclass of core - collapse sne that lack strong hydrogen lines but show helium lines in their spectra. here we present a spectral dataset of eight sne ib, chosen to have at least three pre - maximum spectra, which we call early spectra. our dataset was obtained mainly by the las cumbres observatory ( lco ) and it consists of a total of 82 optical photospheric spectra, including 38 early spectra. this dataset increases the number of published sne ib with at least three early spectra by ~ 60 %. for our classification efforts, we used early spectra in addition to spectra taken around maximum light. we also converted our spectra into sn identification ( snid ) templates and make them available to the community for easier identification of young sne ib. our dataset increases the number of publicly available snid templates of early spectra of sne ib by ~ 43 %. half of our sample has sn types that change over time or are different from what is listed on the transient name server ( tns ). we discuss the implications of our dataset and our findings for current and upcoming sn surveys and their classification efforts.
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arxiv:2409.04522
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in this paper we formulate a contract design problem where a primary license holder wishes to profit from its excess spectrum capacity by selling it to potential secondary users / buyers. it needs to determine how to optimally price the excess spectrum so as to maximize its profit, knowing that this excess capacity is stochastic in nature, does not come with exclusive access, and cannot provide deterministic service guarantees to a buyer. at the same time, buyers are of different { \ em types }, characterized by different communication needs, tolerance for the channel uncertainty, and so on, all of which a buyer ' s private information. the license holder must then try to design different contracts catered to different types of buyers in order to maximize its profit. we address this problem by adopting as a reference a traditional spectrum market where the buyer can purchase exclusive access with fixed / deterministic guarantees. we fully characterize the optimal solution in the cases where there is a single buyer type, and when multiple types of buyers share the same, known channel condition as a result of the primary user activity. in the most general case we construct an algorithm that generates a set of contracts in a computationally efficient manner, and show that this set is optimal when the buyer types satisfy a monotonicity condition.
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arxiv:1207.6445
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we analyze the space - times admitting two shear - free geodesic null congruences. the integrability conditions are presented in a plain tensorial way as equations on the volume element $ u $ of the time - like 2 - - plane that these directions define. from these we easily deduce significant consequences. we obtain explicit expressions for the ricci and weyl tensors in terms of $ u $ and its first and second order covariant derivatives. we study the different compatible petrov - bel types and give the necessary and sufficient conditions that characterize every type in terms of $ u $. the type d case is analyzed in detail and we show that every type d space - time admitting a 2 + 2 conformal killing tensor also admits a conformal killing - yano tensor.
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arxiv:gr-qc/0606015
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we study the evolution of the universe in the presence of inflaton, matter, radiation, and holographic dark energy. the time evolution of the scale factor is obtained by solving the friedmann equation of the universe with a good approximation. we present two independent ways which determine the value of the dark energy constant $ d \ sim 1 $ from the observational data. the two ways are measuring the deceleration parameter and measuring a universal constant depending only on $ d $. the universal constant is given by a dimensionless combination of three scale factors at the equipartition times of radiation - matter, radiation - dark energy, and matter - dark energy. we also discuss that the second law of thermodynamics determines the point of time when the dark energy dominated era begins in the universe.
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arxiv:0804.2579
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we present a modified version of the friends - of - friends ( fof ) structure finding algorithm, designed specifically to locate groups or clusters of galaxies in photometric redshift datasets. the main objective of this paper is to show that this extended friends - of - friends ( hereafter ext - fof ) algorithm yields results almost identical to the original fof, if applied to a spectroscopic redshift dataset, and a rather conservative catalogue of structures, in case of a dataset with simulated photometric redshifts. therefore, we create group catalogues for the first center for astrophysics redshift survey ( cfa1 ), as well as for the las campanas redshift survey ( lcrs ), both of which being spectroscopic surveys, using fof - algorithms. we then apply our new algorithm to said surveys and compare the resulting structure catalogue. furthermore, we bestow simulated photometric redshifts on the lcrs galaxies, and use the ext - fof to detect structures, that we compare in size and composition to the ones found in the original, spectroscopic dataset. we will show that the properties of this modified algorithm are well understood and that it is suited for finding structures in photometric datasets. this is the first paper in a series of papers, dealing with the application of our new cluster finding algorithm to various photometric redshift galaxy surveys.
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arxiv:astro-ph/0312018
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conversational question answering ( cqa ) aims to answer questions contained within dialogues, which are not easily interpretable without context. developing a model to rewrite conversational questions into self - contained ones is an emerging solution in industry settings as it allows using existing single - turn qa systems to avoid training a cqa model from scratch. previous work trains rewriting models using human rewrites as supervision. however, such objectives are disconnected with qa models and therefore more human - like rewrites do not guarantee better qa performance. in this paper we propose using qa feedback to supervise the rewriting model with reinforcement learning. experiments show that our approach can effectively improve qa performance over baselines for both extractive and retrieval qa. furthermore, human evaluation shows that our method can generate more accurate and detailed rewrites when compared to human annotations.
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arxiv:2210.15777
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understanding the nature of neutrino masses will require physics beyond the long - standing standard model of particle physics. neutrinoless double beta decay experiments like the cryogenic underground observatory for rare events ( cuore ) are uniquely suited for probing the remaining mysteries of neutrino mass, particularly the question of the neutrino ' s majorana nature. cuore will be a next - generation experiment at the laboratori nazionali del gran sasso in italy ; it will consist of an array of 988 teo2 detector crystals operated at ~ 10 mk, following the bolometric technique established by the cuoricino experiment. it will look for the energy signal produced by the theoretically - predicted neutrinoless double beta decay in te - 130, and therefore reliable energy calibration of the detector is crucial to the experiment ' s success. we will present the most recent results from cuoricino and discuss the current status of the cuore project, with a particular emphasis on the development of the calibration system.
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arxiv:0910.2994
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the topological phase transition in the qi - wu - zhang model is studied using a real - space approach. an effective hamiltonian for the topologically protected edge - modes in a finite - size system is developed. the topological phase transition is understood in terms of a global perturbation to the system which lifts the degeneracy of the edge - modes. the effective hamiltonian method is also applied to a one - dimensional system with spatially varying hopping strengths to understand the impact of disorder on the edge - modes.
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arxiv:2403.01576
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prediction of the shocks ' arrival times ( sats ) at the earth is very important for space weather forecast. there is a well - known sat model, stoa, which is widely used in the space weather forecast. however, the shock transit time from stoa model usually has a relative large error compared to the real measurements. in addition, stoa tends to yield too much ` yes ' prediction, which causes a large number of false alarms. therefore, in this work, we work on the modification of stoa model. first, we give a new method to calculate the shock transit time by modifying the way to use the solar wind speed in stoa model. second, we develop new criteria for deciding whether the shock will arrive at the earth with the help of the sunspot numbers and the angle distances of the flare events. it is shown that our work can improve the sats prediction significantly, especially the prediction of flare events without shocks arriving at the earth.
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arxiv:1502.01069
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the formation of early - type dwarf ( de ) galaxies, the most numerous objects in clusters, is believed to be closely connected to the physical processes that drive galaxy cluster evolution, like galaxy harassment and ram - pressure stripping. however, the actual significance of each mechanism for building the observed cluster de population is yet unknown. several distinct de subclasses were identified, which show significant differences in their shape, stellar content, and distribution within the cluster. does this diversity imply that des originate from various formation channels? does " cosmological " formation play a role as well? i try to touch on these questions in this brief overview of des in galaxy clusters.
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arxiv:0910.1594
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the internal structure of the resonant lambda ( 1405 ) state is investigated based on meson - baryon coupled - channels chiral dynamics. we evaluate lambda ( 1405 ) form factors which are extracted from current - coupled scattering amplitudes in meson - baryon degrees of freedom. using several probe currents and channel decomposition, we find that the resonant lambda ( 1405 ) state is dominantly composed of widely spread kbar around n, with escaping pi sigma component.
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arxiv:1109.0061
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this theoretical review is intended to give non - theorists a flavor of the ideas driving the current efforts to experimentally find supersymmetry. we discuss the main reasons behind the expectation that supersymmetry may be " just around the corner " and may be discovered in the near future. we use simple quantum - mechanical examples to illustrate the concept - - - and the power - - - of supersymmetry, the possible ways to break supersymmetry, and the dynamical generation of small scales. we then describe how this theoretical machinery helps shape our perception of what physics beyond the electroweak scale might be.
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arxiv:hep-ph/9710274
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topological materials are at the forefront of quantum materials research, offering tremendous potential for next - generation energy and information devices. however, current investigation of these materials remains largely focused on performance and often neglects the crucial aspect of sustainability. recognizing the pivotal role of sustainability in addressing global pollution, carbon emissions, resource conservation, and ethical labor practices, we present a comprehensive evaluation of topological materials based on their sustainability and environmental impact. our approach involves a hierarchical analysis encompassing cost, toxicity, energy demands, environmental impact, social implications, and resilience to imports. by applying this framework to over 16, 000 topological materials, we establish a sustainable topological materials database. our endeavor unveils environmental - friendly topological materials candidates which have been previously overlooked, providing insights into their environmental ramifications and feasibility for industrial scalability. the work represents a critical step toward industrial adoption of topological materials, offering the potential for significant technological advancements and broader societal benefits.
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arxiv:2308.09526
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learning - based perception and prediction modules in modern autonomous driving systems typically rely on expensive human annotation and are designed to perceive only a handful of predefined object categories. this closed - set paradigm is insufficient for the safety - critical autonomous driving task, where the autonomous vehicle needs to process arbitrarily many types of traffic participants and their motion behaviors in a highly dynamic world. to address this difficulty, this paper pioneers a novel and challenging direction, i. e., training perception and prediction models to understand open - set moving objects, with no human supervision. our proposed framework uses self - learned flow to trigger an automated meta labeling pipeline to achieve automatic supervision. 3d detection experiments on the waymo open dataset show that our method significantly outperforms classical unsupervised approaches and is even competitive to the counterpart with supervised scene flow. we further show that our approach generates highly promising results in open - set 3d detection and trajectory prediction, confirming its potential in closing the safety gap of fully supervised systems.
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arxiv:2210.08061
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we present a new development in our approach to the covariant quantization of superstrings in 10 dimensions which is based on a gauged wznw model. to incorporate worldsheet diffeomorphisms we need the quartet of ghosts $ ( b _ { zz }, c ^ { z }, \ b _ { zz }, \ g ^ { z } ) $ for topological gravity. the currents of this combined system form an n = 2 superconformal algebra. the model has vanishing central charge and contains two anticommuting brst charges, $ q _ { s } = q _ { w } + \ oint \ g ^ { z } b _ { zz } + \ oint \ eta _ { z } $ and $ q _ { v } = \ oint c ^ { z } \ big ( t ^ { w } _ { zz } + { 1 \ over 2 } t ^ { top } _ { zz } \ big ) + \ g ^ { z } ( b ^ { w } _ { zz } + { 1 \ over 2 } b ^ { top } _ { zz } \ big ) $, where $ \ eta _ { z } $ is obtained by the usual fermionization of $ \ b _ { zz }, \ g ^ { z } $. physical states form the cohomology of $ q _ { s } + q _ { v } $, have nonnegative grading, and are annihilated by $ b _ { 0 } $ and $ \ beta _ { 0 } $. we no longer introduce any ghosts by hand, and the formalism is completely lorentz covariant.
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arxiv:hep-th/0307056
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a purported ` ai singularity ' has been in the public eye recently. mass media and us national political attention focused on ` ai doom ' narratives hawked by social media influencers. the european commission is announcing initiatives to forestall ` ai extinction '. in my opinion, ` ai singularity ' is the wrong narrative for what ' s happening now ; recent happenings signal something else entirely. something fundamental to computation - based research really changed in the last ten years. in certain fields, progress is dramatically more rapid than previously, as the fields undergo a transition to frictionless reproducibility ( fr ). this transition markedly changes the rate of spread of ideas and practices, affects mindsets, and erases memories of much that came before. the emergence of frictionless reproducibility follows from the maturation of 3 data science principles in the last decade. those principles involve data sharing, code sharing, and competitive challenges, however implemented in the particularly strong form of frictionless open services. empirical machine learning ( eml ) is todays leading adherent field, and its consequent rapid changes are responsible for the ai progress we see. still, other fields can and do benefit when they adhere to the same principles. many rapid changes from this maturation are misidentified. the advent of fr in eml generates a steady flow of innovations ; this flow stimulates outsider intuitions that there ' s an emergent superpower somewhere in ai. this opens the way for pr to push worrying narratives : not only ` ai extinction ', but also the supposed monopoly of big tech on ai research. the helpful narrative observes that the superpower of eml is adherence to frictionless reproducibility practices ; these practices are responsible for the striking progress in ai that we see everywhere.
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arxiv:2310.00865
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we consider the n = 4 sym theory in flat 3 + 1 dimensional spacetime with a time dependent coupling constant which vanishes at $ t = 0 $, like $ g _ { ym } ^ 2 = t ^ p $. in an analogous quantum mechanics toy model we find that the response is singular. the energy diverges at $ t = 0 $, for a generic state. in addition, if $ p > 1 $ the phase of the wave function has a wildly oscillating behavior, which does not allow it to be continued past $ t = 0 $. a similar effect would make the gauge theory singular as well, though nontrivial effects of renormalization could tame this singularity and allow a smooth continuation beyond $ t = 0 $. the gravity dual in some cases is known to be a time dependent cosmology which exhibits a space - like singularity at $ t = 0 $. our results, if applicable in the gauge theory for the case of the vanishing coupling, imply that the singularity is a genuine sickness and does not admit a meaningful continuation. when the coupling remains non - zero and becomes small at $ t = 0 $, the curvature in the bulk becomes of order the string scale. the gauge theory now admits a time evolution beyond this point. in this case, a finite amount of energy is produced which possibly thermalizes and leads to a black hole in the bulk.
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arxiv:0807.1517
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we report a strong - field detection method for magnetic materials, based on the characterization of crystal time - reversal symmetry through the elliptical dichroism of harmonics. the consistency of the low - order harmonics driven by laser fields with opposite helicities originates from the time - reversal symmetry of crystals, and thus the appearance of harmonic elliptical dichroism can serve as evidence for the breaking of crystal time - reversal symmetry. we have used the semiconductor bloch equation to calculate the harmonic spectra of the bilayer ferromagnetic material cr2ge2te6, with and without spin - orbit coupling. in magnetic materials, strong spin - orbit coupling causes the loss of time - reversal symmetry in the phase of polarization currents between different spin states, inducing elliptical dichroism in the harmonics. here we extend the magneto - optical faraday or kerr effect to the nonlinear domain using strong laser fields, improving the sensitivity and applicability of magneto - optical detection methods.
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arxiv:2505.06587
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prior work has shown that text - conditioned diffusion models can learn to identify and manipulate primitive concepts underlying a compositional data - generating process, enabling generalization to entirely novel, out - of - distribution compositions. beyond performance evaluations, these studies develop a rich empirical phenomenology of learning dynamics, showing that models generalize sequentially, respecting the compositional hierarchy of the data - generating process. moreover, concept - centric structures within the data significantly influence a model ' s speed of learning the ability to manipulate a concept. in this paper, we aim to better characterize these empirical results from a theoretical standpoint. specifically, we propose an abstraction of prior work ' s compositional generalization problem by introducing a structured identity mapping ( sim ) task, where a model is trained to learn the identity mapping on a gaussian mixture with structurally organized centroids. we mathematically analyze the learning dynamics of neural networks trained on this sim task and show that, despite its simplicity, sim ' s learning dynamics capture and help explain key empirical observations on compositional generalization with diffusion models identified in prior work. our theory also offers several new insights - - e. g., we find a novel mechanism for non - monotonic learning dynamics of test loss in early phases of training. we validate our new predictions by training a text - conditioned diffusion model, bridging our simplified framework and complex generative models. overall, this work establishes the sim task as a meaningful theoretical abstraction of concept learning dynamics in modern generative models.
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arxiv:2410.08309
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in this paper, we study the universal blind quantum computing ( ubqc ) protocol, which allows a client to perform quantum computation on a remote quantum server and the remote blind qubit state preparation ( rbsp ) protocol which allows the client to prepare single qubits on the server ' s location with week coherent pulses. this rbsp protocol is inefficient for small $ t $, because the required number of pulses for generating one single qubit scales as $ \ mbox { o } ( 1 / t ^ 4 ) $, where $ t $ is the transmittance of the quantum channe between the client and the server. our contribution in this paper is a modified rbsp protocol with decoy states. this new protocol allows us to generate $ s $ single qubits simultaneously in a single instance. with our new rotocol, we are able to reduce the number of weak coherent pulses required for generating one single qubit from $ \ mbox { o } ( 1 / t ^ 4 ) $ to nearly $ \ mbox { o } ( 1 / t ) $, significantly increasing the efficiency. for a 100 km standard telecom fiber of loss 0. 2 db / km, our method gives a six orders of magnitude improvement in the speed, which is very significant.
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arxiv:1508.07910
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we investigated the magnetic and magnetoelastic properties of mnsc $ _ 2 $ se $ _ 4 $ single crystals at low temperature under a magnetic field directed along the crystallographic [ 111 ] axis. the magnetization data at low temperature show a linear increase with magnetic field, until saturation is reached above 15 t. in ultrasound, a longitudinal acoustic mode shows a softening in field, which is absent for a transverse acoustic mode. we discuss these results using a microscopic model based on the framework of linear spin - wave theory. the magnetic and magnetoelastic data are qualitatively reproduced by considering magnon - phonon interactions arising from exchange - striction coupling between the crystal lattice and spin - wave fluctuations in the zero - temperature limit.
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arxiv:2410.20948
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recently, sengupta and ghosh [ phys. fluids 34, 054116, ( 2022 ) ] published a linear stability analysis of a pressure - driven channel flow which is subject to rotation around a spanwise axis and a uniform magnetic field applied in the same direction. unfortunately, the formulation of the magnetohydrodynamic part of the problem contains an elementary error which makes the obtained results unphysical. the error is due to unfounded omission of the electric potential contribution in the induced electric current which, thus, does not satisfy the charge conservation.
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arxiv:2209.15272
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we study the graviton - photon conversion in the magnetic fields of the earth, the milky way galaxy, and intergalactic regions. requiring that the photon flux converted from gravitons does not exceed the observed photon flux with telescopes, we derive upper limits on the stochastic gravitational waves in frequency ranges from $ 10 ^ { 7 } $ hz to $ 10 ^ { 35 } $ hz. remarkably, the upper limits on $ h ^ 2 \ omega _ { { \ rm gw } } $ could be less than unity in the frequency range of $ 10 ^ { 18 } $ - $ 10 ^ { 23 } $ hz in a specific case. the detection of gravitational waves using telescopes would open up a new avenue for high frequency gravitational wave observations.
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arxiv:2309.14765
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primordial gravitational waves are created during the de sitter phase of an exponentially - expanding ( inflationary ) universe, due to quantum zero - point vacuum fluctuations. these waves produce fluctuations in the temperature of the cosmic background radiation ( cbr ). we calculate the multipole moments of the correlation function for these temperature fluctuations in a spatially - closed friedman - robertson - walker ( frw ) cosmological model. the results are compared to the corresponding multipoles in the spatially - flat case. the differences are small unless the density parameter today, $ \ omega _ 0 $, is greater than 2. ( submitted to physical review d ).
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arxiv:astro-ph/9410024
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to provide stable and responsive public sparql query services, data providers enforce quotas on server usage. queries which exceed these quotas are interrupted and deliver partial results. such interruption is not an issue if it is possible to resume queries execution afterward. unfortunately, there is no preemption model for the web that allows for suspending and resuming sparql queries. in this paper, we propose sage : a sparql query engine based on web preemption. sage allows sparql queries to be suspended by the web server after a fixed time quantum and resumed upon client request. web preemption is tractable only if its cost in time is negligible compared to the time quantum. the challenge is to support the full sparql query language while keeping the cost of preemption negligible. experimental results demonstrate that sage outperforms existing sparql query processing approaches by several orders of magnitude in term of the average total query execution time and the time for first results.
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arxiv:1902.04790
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in portfolio analysis, the traditional approach of replacing population moments with sample counterparts may lead to suboptimal portfolio choices. i show that optimal portfolio weights can be estimated using a machine learning ( ml ) framework, where the outcome to be predicted is a constant and the vector of explanatory variables is the asset returns. it follows that ml specifically targets estimation risk when estimating portfolio weights, and that " off - the - shelf " ml algorithms can be used to estimate the optimal portfolio in the presence of parameter uncertainty. the framework nests the traditional approach and recently proposed shrinkage approaches as special cases. by relying on results from the ml literature, i derive new insights for existing approaches and propose new estimation methods. based on simulation studies and several datasets, i find that ml significantly reduces estimation risk compared to both the traditional approach and the equal weight strategy.
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arxiv:1804.01764
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a to - date unsolved and highly limiting safety concern for ultra high - field ( uhf ) magnetic resonance imaging ( mri ) is the deposition of radiofrequency ( rf ) power in the body, quantified by the specific absorption rate ( sar ), leading to dangerous tissue heating / damage in the form of local sar hotspots that cannot currently be measured / monitored, thereby severely limiting the applicability of the technology for clinical practice and in regulatory approval. the goal of this study has been to show proof of concept of an artificial intelligence ( ai ) based exam - integrated real - time mri safety prediction software ( mrsaife ) facilitating the safe generation of 3t and 7t images by means of accurate local sar - monitoring at sub - w / kg levels. we trained the software with a small database of image as a feasibility study and achieved successful proof of concept for both field strengths. sar patterns were predicted with a residual root mean squared error ( rsme ) of < 11 % along with a structural similarity ( ssim ) level of > 84 % for both field strengths ( 3t and 7t ).
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arxiv:2102.01023
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we test an optimised hopping parameter expansion on various z _ 2 lattice scalar field models : the ising model, a spin - one model and lambda ( phi ) ^ 4. we do this by studying the critical indices for a variety of optimisation criteria, in a range of dimensions and with various trial actions. we work up to seventh order, thus going well beyond previous studies. we demonstrate how to use numerical methods to generate the high order diagrams and their corresponding expressions. these are then used to calculate results numerically and, in the case of the ising model, we obtain some analytic results. we highlight problems with several optimisation schemes and show for the best scheme that the critical exponents are consistent with mean field results to at least 8 significant figures. we conclude that in its present form, such optimised lattice expansions do not seem to be capturing the non - perturbative infra - red physics near the critical points of scalar models.
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arxiv:hep-ph/0406202
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for any bott - samelson resolution $ q _ { i } : \ hat { x _ { i } } \ rightarrow g / b $ of the flag variety $ g / b $, and any torus equivariant oriented cohomology $ h _ t $, we compute the restriction formula of certain basis $ \ eta _ l $ of $ h _ t ( \ hat { x _ { i } } ) $ determined by the projective bundle formula. as an application, we show that $ h _ t ( \ hat { x _ { i } } ) $ embeds into the equivariant oriented cohomology of $ t $ - fixed points, and the image can be characterized by using the goresky - kottwitz - macpherson ( gkm ) description. furthermore, we compute the push - forward of the basis $ \ eta _ l $ onto $ h _ t ( g / b ) $, and their restriction formula.
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arxiv:2004.07680
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we report results on electronic transport properties of liquid fe - s alloys at conditions of planetary cores, computed by first - principle techniques in the kubo - greenwood formalism. we describe a combined effect of resistivity saturation due to temperature, compression, and chemistry by comparing the electron mean free path from the drude response of optical conductivity to the mean interatomic distance. at high compression and high sulfur concentration the ioffe - regel condition is satisfied, and the temperature coefficient of resistivity changes sign from positive to negative. we show that this happens due to a decrease of the $ d $ - density of states at the fermi level in response to thermal broadening.
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arxiv:1803.02649
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we study using first - principles calculations the energetics, structural and electronic properties of nitrogen incorporation in sio2. we consider no, nh, n2 and atomic n as the nitriding species interacting with a si - si bond of an otherwise perfect sio2 network in order to simulate the nitrogen incorporation near si / sio2 interface regions. we find that all the species react with the si - si bond forming bridge structures with the si atoms without dissociating, where nh and atomic n form the most stable structures. concerning the electronic properties, our results show that the incorporated nh is the only structure which does not introduce trapping center at the interface. the structures involving no and atomic n are acceptors, whereas that involving n2 may be either a donor or an acceptor. the hydrogen passivation of the electrically active centers is also discussed.
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arxiv:cond-mat/0311323
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we demonstrate a tuneable, chip - scale wavelength reference to greatly reduce the complexity and volume of cold - atom sensors. a 1 mm optical path length micro - fabricated cell provides an atomic wavelength reference, with dynamic frequency control enabled by zeeman shifting the atomic transition through the magnetic field generated by the printed circuit board ( pcb ) coils. the dynamic range of the laser frequency stabilization system is evaluated and used in conjunction with an improved generation of chip - scale cold atom platforms that traps 4 million 87rb atoms. the scalability and component consolidation provide a key step forward in the miniaturization of cold atom sensors.
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arxiv:2212.02853
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the cm - wavelength radio flares on cygnus x - 3 have been studied for many years. our recent paper ( spencer et al., 2022 ) looked again at the minor flares ( flux density s of a few 100 mjy ) and compared their properties with those of a sample of major flares ( s > 1 jy ). we find that the minor flares have rise times and duration of ~ 1 hour, as opposed to ~ days for the major flares. minor flares show more rapid expansion of the synchrotron radiation emitting material than in the strong flares. they also appear closer to the binary, whereas the large flares form a more developed jet, i. e. the jets formed in minor flares are short and wide, those in major flares are long and thin. we used the results of fender & bright ( 2019 ) to calculate the magnetic field and expansion velocity as a fraction b of the speed of light under minimum energy conditions when the source is optically thick for samples of minor and major flares. the minimum power in the source was found using the rise time of the flares. the minor flares have lower minimum power but have larger velocities and energy densities than the major flares. minor flares can occur while a major flare is in progress, suggesting an indirect coupling between them. the spectral evolution of the minor flares can be explained by either an expanding synchrotron source or a shock model. further investigation requires high resolution vlbi observations at the 1 mas level if we wish to understand the development of the source. the problem is that cygnus x - 3 is strongly scattered by the interstellar medium so high frequencies in the several 10s of ghz are required for the resolution needed. the minor flares are rapid [... ] and hence only short snapshot vlbi observations can capture the structure. large numbers of telescopes are required which is a problem at the highest frequencies. we discuss the vlbi possibilities and trade - offs for this awkward object.
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arxiv:2303.07353
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natural radioactivity concentrations in high exposure building materials are commonly used in iran, which is measured a direct exposure by using { \ gamma } - ray spectrometry. the values for 226ra, 232th and 40k were in the ranges 3. 8 - 94. 2, 6. 5 - 172. 2 and 556. 9 - 1539. 2 bqkg - 1, respectively. the absorbed dose rates in the standard dwelling room due to 238u, 232th series and 40k were calculated with mcnpx code. the simulation and experimental results were between 7. 95 - 41. 74 and 8. 36 - 39. 99 ngy h - 1, respectively. these results were compared with experimental outing and there was overlap closely. the simulation results are able to develop for any kind of dwelling places.
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arxiv:1502.04723
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