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gr-qc/9503026
|
Four Dimensional Quantum Topology Changes of Spacetimes
|
We investigate topology changing processes in the WKB approximation of four dimensional quantum cosmology with a negative cosmological constant. As Riemannian manifolds which describe quantum tunnelings of spacetime we consider constant negative curvature solutions of the Einstein equation i.e. hyperbolic geometries. Using four dimensional polytopes, we can explicitly construct hyperbolic manifolds with topologically non-trivial boundaries which describe topology changes. These instanton-like solutions are constructed out of 8-cell's, 16-cell's or 24-cell's and have several points at infinity called cusps. The hyperbolic manifolds are non-compact because of the cusps but have finite volumes. Then we evaluate topology change amplitudes in the WKB approximation in terms of the volumes of these manifolds. We find that the more complicated are the topology changes, the more likely are suppressed.
|
[
"Physics Archive->gr-qc",
"Physics Archive->hep->hep-th"
] | 1995-03-16T07:04:37Z |
2301.02668
|
A Framework for Large Scale Particle Filters Validated with Data Assimilation for Weather Simulation
|
Particle filters are a group of algorithms to solve inverse problems through statistical Bayesian methods when the model does not comply with the linear and Gaussian hypothesis. Particle filters are used in domains like data assimilation, probabilistic programming, neural networkoptimization, localization and navigation. Particle filters estimate the probabilitydistribution of model states by running a large number of model instances, the so called particles. The ability to handle a very large number of particles is critical for high dimensional models.This paper proposes a novel paradigm to run very large ensembles of parallel model instances on supercomputers. The approach combines an elastic and fault tolerant runner/server model minimizing data movementswhile enabling dynamic load balancing. Particle weights are computed locally on each runner andtransmitted when available to a server that normalizes them, resamples new particles based on their weight, and redistributes dynamically the work torunners to react to load imbalance. Our approach relies on a an asynchronously manageddistributed particle cache permitting particles to move from one runner to another inthe background while particle propagation goes on. This also enables the number ofrunners to vary during the execution either in reaction to failures and restarts, orto adapt to changing resource availability dictated by external decision processes.The approach is experimented with the Weather Research and Forecasting (WRF) model, toassess its performance for probabilistic weather forecasting. Up to 2555particles on 20442 compute cores are used to assimilate cloud cover observations into short--range weather forecasts over Europe.
|
[
"Computer Science Archive->cs.DC"
] | 2023-01-06T15:21:49Z |
1501.03427
|
Minimal surfaces in 4-dimensional Lorentzian Damek-Ricci spaces
|
In this paper we will construct a Weierstrass type representation for minimal surfaces in 4-dimensional Lorentzian Damek-Ricci spaces and we give some examples of such surfaces.
|
[
"Mathematics Archive->math.DG"
] | 2015-01-14T17:58:15Z |
1810.10032
|
Negative results for approximation using single layer and multilayer feedforward neural networks
|
We prove a negative result for the approximation of functions defined on compact subsets of $\mathbb{R}^d$ (where $d \geq 2$) using feedforward neural networks with one hidden layer and arbitrary continuous activation function. In a nutshell, this result claims the existence of target functions that are as difficult to approximate using these neural networks as one may want. We also demonstrate an analogous result (for general $d \in \mathbb{N}$) for neural networks with an \emph{arbitrary} number of hidden layers, for activation functions that are either rational functions or continuous splines with finitely many pieces.
|
[
"Computer Science Archive->cs.LG",
"Statistics Archive->stat.ML"
] | 2018-10-23T18:15:50Z |
0812.2451
|
Efficacy of Put and Spd sprayed on leaves from Brassica juncea plants against Cd2+-induced oxidative stress
|
The protective effect exerted by polyamines (Put and Spd) against cadmium (Cd) stress was investigated in Brassica juncea plants. Treatment with CdCl2 (75 micro-Mole) resulted in a rise of Cd accumulation, a decrease of fresh and dry weights in every plant organ, an increase of free polyamine content at limb and stem levels as well as a decrease at root level. On the other hand, the total conjugated polyamine levels in the stem tissues were unaffected by Cd. In the leaf tissues, this metal caused a reduction of chlorophyll a content, a rise of guaiacol peroxidase (GPOX) activity and an increase of malondialdehyde (MDA), soluble glucide, proline and amino acid contents. Exogenous application, by spraying, of putrescine (Put) and spermidine (Spd) to leaf tissues reduced CdCl2-induced stress. These polyamines proved to exert a partial, though significant, protection of the foliar fresh weight and to alleviate the oxidative stress generated by Cd through reductions of MDA amounts and GPOX (E.C.1.11.1.7) activity. The enhancement of chlorophyll a content in plants by Put and those of Chl a and Chl b by Spd both constitute evidences of their efficacy against the Cd2+-induced loss of pigments. Conversely to Put, Spd caused a decrease of Cd content in leave tissues and a rise in the stems and roots; these findings are in favour of a stimulation of Cd uptake by Spd. The proline stimulation observed with Cd was reduced further to the spraying of Put onto tissues, but the decrease induced by Spd was more limited. In the plants treated with Cd, the amino acid contents in the leaves were unaffected by Put and Spd spraying; on the other hand, Cd2+ disturbed polyamine levels (free and acido-soluble conjugated-forms); we notice the rise of total free PAs and the decrease of their conjugated-ones.
|
[
"Quantitative Biology Archive->q-bio.BM"
] | 2008-12-12T18:28:05Z |
2112.15387
|
Complex actions and causality violations: Applications to Lorentzian quantum cosmology
|
For the construction of the Lorentzian path integral for gravity one faces two main questions: Firstly, what configurations to include, in particular whether to allow Lorentzian metrics that violate causality conditions. And secondly, how to evaluate a highly oscillatory path integral over unbounded domains. Relying on Picard-Lefschetz theory to address the second question for discrete Regge gravity, we will illustrate that it can also answer the first question. To this end we will define the Regge action for complexified variables and study its analytical continuation. Although there have been previously two different versions defined for the Lorentzian Regge action, we will show that the complex action is unique. More precisely, starting from the different definitions for the action one arrives at equivalent analytical extensions. The difference between the two Lorentzian versions is only realized along branch cuts which arise for a certain class of causality violating configurations. As an application we discuss the path integral describing a finite evolution step of the discretized deSitter universe. We will in particular consider an evolution from vanishing to finite scale factor, for which the path integral defines the no-boundary wave function.
|
[
"Physics Archive->gr-qc",
"Physics Archive->hep->hep-th"
] | 2021-12-31T11:05:22Z |
2103.02310
|
Asymptotic approximation of the likelihood of stationary determinantal point processes
|
Continuous determinantal point processes (DPPs) are a class of repulsive point processes on $\mathbb{R}^d$ with many statistical applications. Although an explicit expression of their density is known, it is too complicated to be used directly for maximum likelihood estimation. In the stationary case, an approximation using Fourier series has been suggested, but it is limited to rectangular observation windows and no theoretical results support it. In this contribution, we investigate a different way to approximate the likelihood by looking at its asymptotic behaviour when the observation window grows towards $\mathbb{R}^d$. This new approximation is not limited to rectangular windows, is faster to compute than the previous one, does not require any tuning parameter, and some theoretical justifications are provided. It moreover provides an explicit formula for estimating the asymptotic variance of the associated estimator. The performances are assessed in a simulation study on standard parametric models on $\mathbb{R}^d$ and compare favourably to common alternative estimation methods for continuous DPPs.
|
[
"Mathematics Archive->math.ST",
"Statistics Archive->stat.TH"
] | 2021-03-03T10:39:37Z |
1706.02185
|
Synthesizing Filamentary Structured Images with GANs
|
This paper aims at synthesizing filamentary structured images such as retinal fundus images and neuronal images, as follows: Given a ground-truth, to generate multiple realistic looking phantoms. A ground-truth could be a binary segmentation map containing the filamentary structured morphology, while the synthesized output image is of the same size as the ground-truth and has similar visual appearance to what have been presented in the training set. Our approach is inspired by the recent progresses in generative adversarial nets (GANs) as well as image style transfer. In particular, it is dedicated to our problem context with the following properties: Rather than large-scale dataset, it works well in the presence of as few as 10 training examples, which is common in medical image analysis; It is capable of synthesizing diverse images from the same ground-truth; Last and importantly, the synthetic images produced by our approach are demonstrated to be useful in boosting image analysis performance. Empirical examination over various benchmarks of fundus and neuronal images demonstrate the advantages of the proposed approach.
|
[
"Computer Science Archive->cs.CV"
] | 2017-06-07T13:37:09Z |
2112.07964
|
Floquet-engineered pair and single particle filter in the Fermi Hubbard model
|
We investigate the Fermi-Hubbard model with a Floquet-driven impurity in the form of a local time-oscillating potential. For strong attractive interactions a stable formation of pairs is observed. These pairs show a completely different transmission behavior than the transmission that is observed for the single unpaired particles. Whereas in the high frequency limit the single particles show a maximum of the transition at low driving amplitudes, the pairs display a pronounced maximum transmission when the amplitude of the driving lies close to the ratio of the interaction U and the driving frequency {\omega}. We use the distinct transmission behaviour to design filters for pairs or single particles, respectively. For example one can totally block the transmission of single particles through the driven impurity and allow only for the transmission of pairs. We quantify the quality of the designed filters.
|
[
"Physics Archive->cond-mat->cond-mat.quant-gas"
] | 2021-12-15T08:35:39Z |
1111.2257
|
Universal bridge functional for infinitely diluted solutions: a case study for Lennard-Jones spheres of different diameter
|
In the paper we propose an universal bridge functional for the closure of the Ornstein-Zernike (OZ) equation for the case of infinitely diluted solutions of Lennard-Jones shperes of different size in the Lennard-Jones fluid. Bridge functional is paprameterized using the data of the Molecular Dynamics (MD) simulations. We show that for all investigated systems the bridge functional can be efficiently papameterized with the exponential function which depends only on the ratio of sizes of the solute and solvent atoms. To check the parameterization we solve the OZ equation with the closure which includes the parametrized functional and with the closure without the bridge functional (Hyper-netted chain closure). We show that introducing the bridge functional allows to obtain radial distribution functions (RDFs), which are close to the MD results and essentially improve predictions of the location and height of the first peak of the RDF.
|
[
"Physics Archive->cond-mat->cond-mat.stat-mech"
] | 2011-11-09T16:19:05Z |
1803.11317
|
Scalar charges and the first law of black hole thermodynamics
|
We present a variational formulation of Einstein-Maxwell-dilaton theory in flat spacetime, when the asymptotic value of the scalar field is not fixed. We obtain the boundary terms that make the variational principle well posed and then compute the finite gravitational action and corresponding Brown-York stress tensor. We show that the total energy has a new contribution that depends of the asymptotic value of the scalar field and discuss the role of scalar charges for the first law of thermodynamics. We also extend our analysis to hairy black holes in Anti-de Sitter spacetime and investigate the thermodynamics of an exact solution that breaks the conformal symmetry of the boundary.
|
[
"Physics Archive->hep->hep-th"
] | 2018-03-30T02:16:49Z |
1905.12731
|
Protecting quantum entanglement from leakage and qubit errors via repetitive parity measurements
|
Protecting quantum information from errors is essential for large-scale quantum computation. Quantum error correction (QEC) encodes information in entangled states of many qubits, and performs parity measurements to identify errors without destroying the encoded information. However, traditional QEC cannot handle leakage from the qubit computational space. Leakage affects leading experimental platforms, based on trapped ions and superconducting circuits, which use effective qubits within many-level physical systems. We investigate how two-transmon entangled states evolve under repeated parity measurements, and demonstrate the use of hidden Markov models to detect leakage using only the record of parity measurement outcomes required for QEC. We show the stabilization of Bell states over up to 26 parity measurements by mitigating leakage using postselection, and correcting qubit errors using Pauli-frame transformations. Our leakage identification method is computationally efficient and thus compatible with real-time leakage tracking and correction in larger quantum processors.
|
[
"Physics Archive->quant-ph"
] | 2019-05-29T21:11:06Z |
1108.3211
|
Observation of the baryonic B decay B0bar --> Lambda_c^+ anti-Lambda K-
|
We report the observation of the baryonic B decay B0bar --> Lambda_c^+ anti-Lambda K- with a significance larger than 7 standard deviations based on 471x10^6$ BBbar pairs collected with the BABAR detector at the PEP-II storage ring at SLAC. We measure the branching fraction for the decay B0bar --> Lambda_c^+ anti-Lambda K- to be (3.8 \pm 0.8_{stat} \pm 0.2_{sys} \pm 1.0_{Lambda_c^+})x10^{-5}. The uncertainties are statistical, systematic, and due to the uncertainty in the Lambda_c^+ branching fraction. We find that the Lambda_c^+ K^- invariant mass distribution shows an enhancement above 3.5 GeV/c^2.
|
[
"Physics Archive->hep->hep-ex"
] | 2011-08-16T11:53:17Z |
1709.05400
|
Multiplicity results for a quasilinear equation with singular nonlinearity
|
For an open, bounded domain $\Om$ in $\mathbb{R}^N$ which is strictly convex with $C^2$ boundary, we show that there exists a $\land>0$ such that the singular quasilinear problem \begin{eqnarray*} &-\delp u =\cfrac{\lambda}{u^{\del}}+u^q\,\,\mbox{in}\,\,\Om\\ &u=0\,\,\mbox{on}\,\,\partial\Om;\, \,\,u>0\,\,\mbox{in}\,\,\Om \end{eqnarray*} admits atleast two solution $ u$ and $v$ in $W^{1,p}_{loc}(\Om)\cap L^{\infty}(\Om)$ for any $\del>0$ and $0<\lam<\land$ provided $1<p<N$ and $p-1<q<\frac{p(N-1)}{N-p}-1$.\\ Moreover the solutions $u$ and $v$ are such that $u^{\alp}$ and $v^{\alp}$ are in $W^{1,p}_0(\Om)$ for some $\alp>0$.
|
[
"Mathematics Archive->math.AP"
] | 2017-09-15T20:51:21Z |
2007.14984
|
Cosmological Model Parameter Dependence of the Matter Power Spectrum Covariance from the DEUS-PUR $Cosmo$ Simulations
|
Future galaxy surveys will provide accurate measurements of the matter power spectrum across an unprecedented range of scales and redshifts. The analysis of these data will require one to accurately model the imprint of non-linearities of the matter density field. In particular, these induce a non-Gaussian contribution to the data covariance that needs to be properly taken into account to realise unbiased cosmological parameter inference analyses. Here, we study the cosmological dependence of the matter power spectrum covariance using a dedicated suite of N-body simulations, the Dark Energy Universe Simulation - Parallel Universe Runs (DEUS-PUR) {\it Cosmo}. These consist of 512 realizations for 10 different cosmologies where we vary the matter density $\Omega_m$, the amplitude of density fluctuations $\sigma_8$, the reduced Hubble parameter $h$ and a constant dark energy equation of state $w$ by approximately $10\%$. We use these data to evaluate the first and second derivatives of the power spectrum covariance with respect to a fiducial $\Lambda$CDM cosmology. We find that the variations can be as large as $150\%$ depending on the scale, redshift and model parameter considered. By performing a Fisher matrix analysis we explore the impact of different choices in modelling the cosmological dependence of the covariance. Our results suggest that fixing the covariance to a fiducial cosmology can significantly affect the recovered parameter errors and that modelling the cosmological dependence of the variance while keeping the correlation coefficient fixed can alleviate the impact of this effect.
|
[
"Physics Archive->astro-ph->astro-ph.CO"
] | 2020-07-29T17:52:11Z |
2102.10958
|
Bilingual Language Modeling, A transfer learning technique for Roman Urdu
|
Pretrained language models are now of widespread use in Natural Language Processing. Despite their success, applying them to Low Resource languages is still a huge challenge. Although Multilingual models hold great promise, applying them to specific low-resource languages e.g. Roman Urdu can be excessive. In this paper, we show how the code-switching property of languages may be used to perform cross-lingual transfer learning from a corresponding high resource language. We also show how this transfer learning technique termed Bilingual Language Modeling can be used to produce better performing models for Roman Urdu. To enable training and experimentation, we also present a collection of novel corpora for Roman Urdu extracted from various sources and social networking sites, e.g. Twitter. We train Monolingual, Multilingual, and Bilingual models of Roman Urdu - the proposed bilingual model achieves 23% accuracy compared to the 2% and 11% of the monolingual and multilingual models respectively in the Masked Language Modeling (MLM) task.
|
[
"Computer Science Archive->cs.CL"
] | 2021-02-22T12:56:37Z |
1704.00794
|
Time Series Cluster Kernel for Learning Similarities between Multivariate Time Series with Missing Data
|
Similarity-based approaches represent a promising direction for time series analysis. However, many such methods rely on parameter tuning, and some have shortcomings if the time series are multivariate (MTS), due to dependencies between attributes, or the time series contain missing data. In this paper, we address these challenges within the powerful context of kernel methods by proposing the robust \emph{time series cluster kernel} (TCK). The approach taken leverages the missing data handling properties of Gaussian mixture models (GMM) augmented with informative prior distributions. An ensemble learning approach is exploited to ensure robustness to parameters by combining the clustering results of many GMM to form the final kernel. We evaluate the TCK on synthetic and real data and compare to other state-of-the-art techniques. The experimental results demonstrate that the TCK is robust to parameter choices, provides competitive results for MTS without missing data and outstanding results for missing data.
|
[
"Computer Science Archive->cs.LG",
"Statistics Archive->stat.ML"
] | 2017-04-03T20:16:58Z |
2307.01567
|
Once-Training-All-Fine: No-Reference Point Cloud Quality Assessment via Domain-relevance Degradation Description
|
Full-reference (FR) point cloud quality assessment (PCQA) has achieved impressive progress in recent years. However, as reference point clouds are not available in many cases, no-reference (NR) metrics have become a research hotspot. Existing NR methods suffer from poor generalization performance. To address this shortcoming, we propose a novel NR-PCQA method, Point Cloud Quality Assessment via Domain-relevance Degradation Description (D$^3$-PCQA). First, we demonstrate our model's interpretability by deriving the function of each module using a kernelized ridge regression model. Specifically, quality assessment can be characterized as a leap from the scattered perceptual domain (reflecting subjective perception) to the ordered quality domain (reflecting mean opinion score). Second, to reduce the significant domain discrepancy, we establish an intermediate domain, the description domain, based on insights from subjective experiments, by considering the domain relevance among samples located in the perception domain and learning a structured latent space. The anchor features derived from the learned latent space are generated as cross-domain auxiliary information to promote domain transformation. Furthermore, the newly established description domain decomposes the NR-PCQA problem into two relevant stages. These stages include a classification stage that gives the degradation descriptions to point clouds and a regression stage to determine the confidence degrees of descriptions, providing a semantic explanation for the predicted quality scores. Experimental results demonstrate that D$^3$-PCQA exhibits robust performance and outstanding generalization ability on several publicly available datasets. The code in this work will be publicly available at https://smt.sjtu.edu.cn.
|
[
"Electrical Engineering and Systems Science Archive->eess.IV"
] | 2023-07-04T08:42:58Z |
2003.05125
|
Single-Carrier Transport in Graphene/hBN Superlattices
|
Graphene/hexagonal boron nitride (hBN) moir\'e superlattices have attracted interest for use in the study of many-body effects and fractal physics in Dirac fermion systems. Many exotic transport properties have been intensively examined in such superlattices, but previous studies have not focused on single-carrier transport. The investigation of the single-carrier behavior in these superlattices would lead to an understanding of the transition of single-particle/correlated phenomena. Here, we show the single-carrier transport in a high-quality bilayer graphene/hBN superlattice-based quantum dot device. We demonstrate remarkable device controllability in the energy range near the charge neutrality point (CNP) and the hole-side satellite point. Under a perpendicular magnetic field, Coulomb oscillations disappear near the CNP, which could be a signature of the crossover between Coulomb blockade and quantum Hall regimes. Our results pave the way for exploring the relationship of single-electron transport and fractal quantum Hall effects with correlated phenomena in two-dimensional quantum materials.
|
[
"Physics Archive->cond-mat->cond-mat.mes-hall"
] | 2020-03-11T06:05:18Z |
1504.07425
|
Interfacial adsorption in Potts models on the square lattice
|
We study the effect of interfacial phenomena in two-dimensional perfect and random (or disordered) $q$-state Potts models with continuous phase transitions, using, mainly, Monte Carlo techniques. In particular, for the total interfacial adsorption, the critical behavior, including corrections to scaling, are analyzed. The role of randomness is scrutinized. Results are discussed applying scaling arguments and invoking findings for bulk critical properties. In all studied cases, i.e., $q = 3$, $4$, and $q = 8$, the spread of the interfacial adsorption profiles is observed to increase linearly with the lattice size at the bulk transition point.
|
[
"Physics Archive->cond-mat->cond-mat.stat-mech"
] | 2015-04-28T11:06:02Z |
astro-ph/0602392
|
An Active Gain-control System for Avalanche Photo-Diodes under Moderate Temperature Variations
|
Avalanche photodiodes (APDs) are promising light sensor for various fields of experimental physics. It has been argued, however, that variation of APD gain with temperature could be a serious problem preventing APDs from replacing traditional photomultiplier tubes (PMTs) in some applications. Here we develop an active gain-control system to keep the APD gain stable under moderate temperature variations. As a performance demonstration of the proposed system, we have tested the response of a scintillation photon detector consisting of a 5x5 mm^2 reverse-type APD optically coupled with a CsI(Tl) crystal. We show that the APD gain was successfully controlled under a temperature variation of DT = 20deg, within a time-cycle of 6000 sec. The best FWHM energy resolution of 6.1+-0.2 % was obtained for 662 keV gamma-rays, and the energy threshold was as low as 6.5 keV, by integrating data from +20deg - 0deg cycles. The corresponding values for -20deg - 0deg cycles were 6.9+-0.2 % and 5.2 keV, respectively. These results are comparable, or only slightly worse than that obtained at a fixed temperature. Our results suggest new potential uses for APDs in various space researches and nuclear physics. As examples, we briefly introduce the NeXT and Cute-1.7 satellite missions that will carry the APDs as scientific instruments for the first time.
|
[
"Physics Archive->astro-ph"
] | 2006-02-17T11:56:29Z |
cond-mat/0006416
|
Time-dependent Gutzwiller approximation for the Hubbard model
|
We develop a time-dependent Gutzwiller approximation (GA) for the Hubbard model analogous to the time-dependent Hartree-Fock (HF) method. The formalism incorporates ground state correlations of the random phase approximation (RPA) type beyond the GA. Static quantities like ground state energy and double occupancy are in excellent agreement with exact results in one dimension up to moderate coupling and in two dimensions for all couplings. We find a substantial improvement over traditional GA and HF+RPA treatments. Dynamical correlation functions can be easily computed and are also substantially better than HF+RPA ones and obey well behaved sum rules.
|
[
"Physics Archive->cond-mat->cond-mat.str-el"
] | 2000-06-27T11:54:09Z |
0711.0944
|
The space of tropically collinear points is shellable
|
The space T_{d,n} of n tropically collinear points in a fixed tropical projective space TP^{d-1} is equivalent to the tropicalization of the determinantal variety of matrices of rank at most 2, which consists of real d x n matrices of tropical or Kapranov rank at most 2, modulo projective equivalence of columns. We show that it is equal to the image of the moduli space M_{0,n}(TP^{d-1},1) of n-marked tropical lines in TP^{d-1} under the evaluation map. Thus we derive a natural simplicial fan structure for T_{d,n} using a simplicial fan structure of M_{0,n}(TP^{d-1},1) which coincides with that of the space of phylogenetic trees on d+n taxa. The space of phylogenetic trees has been shown to be shellable by Trappmann and Ziegler. Using a similar method, we show that T_{d,n} is shellable with our simplicial fan structure and compute the homology of the link of the origin. The shellability of T_{d,n} has been conjectured by Develin in 2005.
|
[
"Mathematics Archive->math.AG",
"Mathematics Archive->math.CO"
] | 2007-11-06T18:37:59Z |
2212.06878
|
Improving our understanding of the Klein-Gordon equation
|
A detailed consideration of the Klein-Gordon equation in relativistic quantum mechanics is presented in order to offer more clarity than many standard approaches. The equation is frequently employed in the research literature, even though problems have often been raised regarding its second-order nature, the status of its negative-energy solutions and the formulation of particle density and flux. Most of these problems can be avoided by dismissing the negative-energy solutions. An application of the equation to a broad wave-packet shows that a small amendment to the usual relativistic formalism can be helpful to demonstrate continuity with the non-relativistic case, although difficulties remain when the proposed quantum state has a broad relativistic energy distribution.
|
[
"Physics Archive->hep->hep-th",
"Physics Archive->quant-ph"
] | 2022-12-13T19:49:20Z |
1212.2827
|
Robust topological insulator surface conduction under strong surface disorder
|
Topological insulators are characterized by specially protected conduction on their outer boundaries. We show that the protected edge conduction exhibited by 2-D topological insulators (and also Chern insulators) is independent of non-magnetic boundary disorder. In particular, the edge states residing inside the bulk gap remain conducting even when edge state inhomogeneities destroy the characteristic linear Dirac relation between energy and momentum. The main effects of boundary disorder on the in-gap states are to decrease the Fermi velocity, increase the density of states, pull the states into the disordered region if spin is conserved, and at very large disorder shift the states to the boundary between the disordered edge and the clean bulk. These effects, which may be useful for device engineering, are controlled by a resonance between the disordered edge and the bulk bands. The resonance's energy is set by the bulk band width; protection of the in-gap edge states' plane-wave character is controlled by the bulk band width, not the bulk band gap.
|
[
"Physics Archive->cond-mat->cond-mat.mes-hall"
] | 2012-12-12T14:37:22Z |
1510.08325
|
The Herschel Point Source Catalogue
|
The Herschel Space Observatory was the fourth cornerstone mission in the European Space Agency (ESA) science programme with excellent broad band imaging capabilities in the sub-mm and far-infrared part of the spectrum. Although the spacecraft finished its observations in 2013, it left a large legacy dataset that is far from having been fully scrutinised and still has a large potential for new scientific discoveries. This is specifically true for the photometric observations of the PACS and SPIRE instruments. Some source catalogues have already been produced by individual observing programs, but there are many observations that risk to remain unexplored. To maximise the science return of the SPIRE and PACS data sets, we are in the process of building the Herschel Point Source Catalogue (HPSC) from all primary and parallel mode observations. Our homogeneous source extraction enables a systematic and unbiased comparison of sensitivity across the different Herschel fields that single programs will generally not be able to provide. The catalogue will be made available online through archives like the Herschel Science Archive (HSA), the Infrared Science Archive (IRSA), and the Strasbourg Astronomical Data Center (CDS).
|
[
"Physics Archive->astro-ph->astro-ph.GA",
"Physics Archive->astro-ph->astro-ph.IM"
] | 2015-10-27T07:21:56Z |
1611.04203
|
Polar Coding for Non-Stationary Channels
|
The problem of polar coding for an arbitrary sequence of independent binary-input memoryless symmetric (BMS) channels $\left\{W_i\right\}_{i=1}^{N}$ is considered. The sequence of channels is assumed to be completely known to both the transmitter and the receiver (a coherent scenario). Also, at each code block transmission, each of the channels is used only once. In other words, a codeword of length $N$ is constructed and then the $i$-th encoded bit is transmitted over $W_i$. The goal is to operate at a rate $R$ close to the average of the symmetric capacities of $W_i$'s, denoted by $\overline{I}_N$. To this end, we construct a polar coding scheme using Arikan's channel polarization transform in combination with certain permutations at each polarization level and certain skipped operations. In particular, given a non-stationary sequence of BMS channels $\left\{W_i\right\}_{i=1}^{N}$ and $P_e$, where $0 < P_e <1$, we construct a polar code of length $N$ and rate $R$ guaranteeing a block error probability of at most $P_e$ for transmission over $\left\{W_i\right\}_{i=1}^{N}$ such that $$ N \leq \frac{\kappa}{(\overline{I}_N - R)^{\mu}}, $$ where $\mu$ is a constant and $\kappa$ is a constant depending on $P_e$ and $\mu$. We further show a numerical upper bound on $\mu$ that is: $\mu \leq 7.34$ for non-stationary binary erasure channels and $\mu \leq 8.54$ for general non-stationary BMS channels. The encoding and decoding complexities of the constructed polar code preserve $O(N \log N)$ complexity of Arikan's polar codes. In an asymptotic sense, when coded bits are transmitted over a non-stationary sequence of BMS channels $\left\{W_i\right\}_{i=1}^{\infty}$, our proposed scheme achieves the average symmetric capacity $$ \overline{I}(\left\{W_i\right\}_{i=1}^{\infty}) := \lim_{N\rightarrow \infty} \frac{1}{N}\sum_{i=1}^N I(W_i), $$ assuming that the limit exists.
|
[
"Computer Science Archive->cs.IT",
"Mathematics Archive->math.IT"
] | 2016-11-13T23:16:57Z |
hep-th/9911206
|
Nonlinear Instantons from Supersymmetric p-Branes
|
Supersymmetric configurations of type II D-branes with nonzero gauge field strengths in general supersymmetric backgrounds with nonzero B fields are analyzed using the kappa-symmetric worldvolume action. It is found in dimension four or greater that the usual instanton equation for the gauge field obtains a nonlinear deformation. The deformation is parameterized by the topological data of the B-field, the background geometry and the cycle wrapped by the brane. In the appropriate dimensions, limits and settings these equations reduce to deformed instanton equations recently found in the context of noncommutative geometry as well as those following from Lagrangians based on Bott-Chern forms. We further consider instantons comprised of M5-branes wrapping a Calabi-Yau space with non-vanishing three-form field strengths. It is shown that the instanton equations for the three-form are related to the Kodaira-Spencer equations.
|
[
"Physics Archive->hep->hep-th"
] | 1999-11-25T16:15:38Z |
1003.4170
|
Analogies in theoretical physics
|
Analogies have had and continue to have an important role in the development of theoretical physics. They may start from similarities of physical concepts followed by similarities in the mathematical formalization or it may be a purely mathematical aspect to suggest the development of analogous physical concepts. More often a subtle non obvious interplay between these levels is involved. In this paper I will discuss two cases sufficiently intricate to illustrate some ways of how analogies work. The first topic is the introduction of spontaneous symmetry breaking in particle physics. The second one is the use of the renormalization group in the theory of critical phenomena and its statistical interpretation.
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[
"Physics Archive->cond-mat->cond-mat.stat-mech",
"Physics Archive->hep->hep-th"
] | 2010-03-22T14:15:25Z |
2103.01836
|
Tame topology in Hensel minimal structures
|
We are concerned with topology of Hensel minimal structures on non-trivially valued fields $K$, whose axiomatic theory was introduced in a recent paper by Cluckers-Halupczok-Rideau. We additionally require that the value group and residue field are orthogonal and that the definable sets in the value group sort are already definable in the language of ordered groups. This condition is satisfied by several classical tame structures on Henselian fields, including Henselian fields with analytic structure, V-minimal fields and polynomially bounded o-minimal structures with a convex subring. In this article, we establish many results concerning definable functions and sets. These are, among others, existence of the limit for definable functions of one variable, a closedness theorem, several non-Archimedean versions of the Lojasiewicz inequalities, theorems on extending continuous definable functions and on existence of definable retractions, an embedding theorem for regular definable spaces and the definable ultranormality and ultraparacompactness of definable Hausdorff LC-spaces.
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[
"Mathematics Archive->math.AG"
] | 2021-03-02T16:22:21Z |
0901.0462
|
Toward explanation of the X-ray - radio correlation in the Vela pulsar
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Recent observations of the Vela pulsar have revealed a peculiar connection of its emission in the soft X-ray and radio ranges. We suggest the model of the radio pulse formation in the Vela pulsar, develop the theory of the radio photon reprocessing to high energies and on this basis interpret the observed X-ray - radio connection. The processes of spontaneous and induced scattering of radio waves off the spiraling particles and their observational consequences are examined. The particles are assumed to acquire relativistic gyration energies due to resonant absorption of the radio emission in the outer magnetosphere of a pulsar. The spectral and angular distributions of the spontaneously scattered power are analyzed and compared with the characteristics of the particle synchrotron emission. The consequences of intensity transfer from the radio beam to the background in the course of induced scattering are studied as well. It is demonstrated that the induced scattering can account for the basic features of the Vela's radio profile and its pulse-to-pulse fluctuations. In particular, it can explain a greater role of the leading component and its earlier arrival in stronger pulses. The studies of the radio photon reprocessing to high energies in application to the Vela pulsar shows that the scattered and synchrotron spectra peak at 0.8 and 0.2 keV, respectively, with the corresponding luminosities of 10^{29} erg s^{-1} and 10^{31} erg s^{-1}. Within the framework of our model, the observed X-ray - radio connection is explained in terms of the interplay between the processes of induced and spontaneous scattering of the radio pulse.
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[
"Physics Archive->astro-ph->astro-ph.HE"
] | 2009-01-05T11:07:31Z |
1405.6964
|
Properties of Generalized Forchheimer Flows in Porous Media
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The nonlinear Forchheimer equations are used to describe the dynamics of fluid flows in porous media when Darcy's law is not applicable. In this article, we consider the generalized Forchheimer flows for slightly compressible fluids and study the initial boundary value problem for the resulting degenerate parabolic equation for pressure with the time-dependent flux boundary condition. We estimate $L^\infty$-norm for pressure and its time derivative, as well as other Lebesgue norms for its gradient and second spatial derivatives. The asymptotic estimates as time tends to infinity are emphasized. We then show that the solution (in interior $L^\infty$-norms) and its gradient (in interior $L^{2-\delta}$-norms) depend continuously on the initial and boundary data, and coefficients of the Forchheimer polynomials. These are proved for both finite time intervals and time infinity. The De Giorgi and Ladyzhenskaya-Uraltseva iteration techniques are combined with uniform Gronwall-type estimates, specific monotonicity properties, suitable parabolic Sobolev embeddings and a new fast geometric convergence result.
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[
"Mathematics Archive->math.AP"
] | 2014-05-27T16:02:47Z |
1505.00086
|
Blow-up phenomena and local well-posedness for a generalized Camassa-Holm equation
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In this paper we mainly study the Cauchy problem for a generalized Camassa-Holm equation. First, by using the Littlewood-Paley decomposition and transport equations theory, we establish the local well-posedness for the Cauchy problem of the equation in Besov spaces. Then we give a simply blow-up criterion for the Cauchy problem of the equation. we present a blow-up result and the exact blow-up rate of strong solutions to the equation by making use of the conservation law and the obtained blow-up criterion.Finally, we verify that the system possesses peakon solutions.
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[
"Mathematics Archive->math.AP"
] | 2015-05-01T04:47:30Z |
2006.04083
|
Asymmetric Jet launching
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In resistive and viscous magnetohydrodynamical (MHD) simulations we obtain axial jets launched from the innermost magnetosphere of a star-disk system. We found that in a part of the parameter space continuous asymmetric jets, which are propagating in opposite directions, are launched. We compare the speed of propagation and rotation of obtained jets with recent observational results.
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[
"Physics Archive->astro-ph->astro-ph.HE"
] | 2020-06-07T08:28:13Z |
1209.2193
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Medium effects in direct reactions
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We discuss medium corrections of the nucleon-nucleon (NN) cross sections and their influence on direct reactions at intermediate energies $\gtrsim 50$ MeV/nucleon. The results obtained with free NN cross sections are compared with those obtained with a geometrical treatment of Pauli-blocking and with NN cross sections obtained with Dirac-Bruecker methods. We show that medium corrections may lead to sizable modifications for collisions at intermediate energies and that they are more pronounced in reactions involving weakly bound nuclei.
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[
"Physics Archive->nucl->nucl-th"
] | 2012-09-11T01:31:16Z |
1602.05198
|
Pinning of Fermionic Occupation Numbers: General Concepts and One Dimension
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Analytical evidence for the physical relevance of generalized Pauli constraints (GPCs) has recently been provided in [PRL 110, 040404]: Natural occupation numbers $\vec{\lambda}\equiv (\lambda_i)$ of the ground state of a model system in the regime of weak couplings $\kappa$ of three spinless fermions in one spatial dimension were found extremely close, in a distance $D_{min}\sim \kappa^8$ to the boundary of the allowed region. We provide a self-contained and complete study of this quasipinning phenomenon. In particular, we develop tools for its systematic exploration and quantification. We confirm that quasipinning in one dimension occurs also for larger particle numbers and extends to intermediate coupling strengths, but vanishes for very strong couplings. We further explore the non-triviality of our findings by comparing quasipinning by GPCs to potential quasipinning by the less restrictive Pauli exclusion principle constraints. This allows us to eventually confirm the significance of GPCs beyond Pauli's exclusion principle.
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[
"Physics Archive->quant-ph"
] | 2016-02-16T21:00:04Z |
1509.06167
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Parallel Query in the Suffix Tree
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Given the query string of length $m$, we explore a parallel query in a static suffix tree based data structure for $p \ll n$, where $p$ is the number of processors and $n$ is the length of the text. We present three results on CREW PRAM. The parallel query in the suffix trie requires $O(m + p)$ work, $O(m/p + \lg p)$ time and $O(n^2)$ space in the worst case. We extend the same technique to the suffix tree where we show it is, by design, inherently sequential in the worst case. Finally we perform the parallel query using an interleaved approach and achieve $O(m \lg p)$ work, $O(\frac{m}{p} \lg p)$ time and $O(n \lg p)$ space in the worst case.
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[
"Computer Science Archive->cs.DS"
] | 2015-09-21T10:02:39Z |
1906.08286
|
Incorporating Priors with Feature Attribution on Text Classification
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Feature attribution methods, proposed recently, help users interpret the predictions of complex models. Our approach integrates feature attributions into the objective function to allow machine learning practitioners to incorporate priors in model building. To demonstrate the effectiveness our technique, we apply it to two tasks: (1) mitigating unintended bias in text classifiers by neutralizing identity terms; (2) improving classifier performance in a scarce data setting by forcing the model to focus on toxic terms. Our approach adds an L2 distance loss between feature attributions and task-specific prior values to the objective. Our experiments show that i) a classifier trained with our technique reduces undesired model biases without a trade off on the original task; ii) incorporating priors helps model performance in scarce data settings.
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[
"Computer Science Archive->cs.CL"
] | 2019-06-19T18:08:06Z |
2312.01985
|
UniGS: Unified Representation for Image Generation and Segmentation
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This paper introduces a novel unified representation of diffusion models for image generation and segmentation. Specifically, we use a colormap to represent entity-level masks, addressing the challenge of varying entity numbers while aligning the representation closely with the image RGB domain. Two novel modules, including the location-aware color palette and progressive dichotomy module, are proposed to support our mask representation. On the one hand, a location-aware palette guarantees the colors' consistency to entities' locations. On the other hand, the progressive dichotomy module can efficiently decode the synthesized colormap to high-quality entity-level masks in a depth-first binary search without knowing the cluster numbers. To tackle the issue of lacking large-scale segmentation training data, we employ an inpainting pipeline and then improve the flexibility of diffusion models across various tasks, including inpainting, image synthesis, referring segmentation, and entity segmentation. Comprehensive experiments validate the efficiency of our approach, demonstrating comparable segmentation mask quality to state-of-the-art and adaptability to multiple tasks. The code will be released at \href{https://github.com/qqlu/Entity}{https://github.com/qqlu/Entity}.
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[
"Computer Science Archive->cs.CV"
] | 2023-12-04T15:59:27Z |
2204.00421
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Missed ferroelectricity in methylammonium lead iodide
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Methylammonium lead iodide, as related organometal halide perovskites, emerged recently as a particularly attractive material for photovoltaic applications. The origin of its appealing properties is sometimes assigned to its potential ferroelectric character, which remains however a topic of intense debate. Here, we rationalize from first-principles calculations how the spatial arrangement of methylammonium polar molecules is progressively constrained by the subtle interplay between their tendency to bond with the inorganic framework and the appearance of iodine octahedra rotations inherent to the perovskite structure. The disordered tetragonal phase observed at room temperature is paraelectric. We show that it should a priori become ferroelectric but that iodine octahedra rotations drive the system toward an antipolar orthorhombic ground state, making it a missed ferroelectric.
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[
"Physics Archive->cond-mat->cond-mat.mtrl-sci"
] | 2022-04-01T13:29:59Z |
1511.02524
|
Dark Matter from the vector of SO(10)
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SO(10) grand unified theories can ensure the stability of new particles in terms of the gauge group structure itself, and in this respect are well suited to accommodate dark matter (DM) candidates in the form of new stable massive particles. We introduce new fermions in two vector 10 representations. When SO(10) is broken to the standard model by a minimal 45 + 126 + 10 scalar sector with $SU(3)_C \otimes SU(2)_L \otimes SU(2)_R\otimes U(1)_{B-L}$ as intermediate symmetry group, the resulting lightest new states are two Dirac fermions corresponding to combinations of the neutral members of the $SU(2)_L$ doublets in the 10's, which get splitted in mass by loop corrections involving $W_R$. The resulting lighter mass eigenstate is stable, and has only non-diagonal $Z_{L,R}$ neutral current couplings to the heavier neutral state. Direct detection searches are evaded if the mass splitting is sufficiently large to suppress kinematically inelastic light-to-heavy scatterings. By requiring that this condition is satisfied, we obtain the upper limit $M_{W_R} \lesssim 25$ TeV.
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[
"Physics Archive->hep->hep-ph"
] | 2015-11-08T20:46:43Z |
1905.11933
|
A Survey of Data Fusion in Smart City Applications
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The advancement of various research sectors such as Internet of Things (IoT), Machine Learning, Data Mining, Big Data, and Communication Technology has shed some light in transforming an urban city integrating the aforementioned techniques to a commonly known term - Smart City. With the emergence of smart city, plethora of data sources have been made available for wide variety of applications. The common technique for handling multiple data sources is data fusion, where it improves data output quality or extracts knowledge from the raw data. In order to cater evergrowing highly complicated applications, studies in smart city have to utilize data from various sources and evaluate their performance based on multiple aspects. To this end, we introduce a multi-perspectives classification of the data fusion to evaluate the smart city applications. Moreover, we applied the proposed multi-perspectives classification to evaluate selected applications in each domain of the smart city. We conclude the paper by discussing potential future direction and challenges of data fusion integration.
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[
"Electrical Engineering and Systems Science Archive->eess.SP"
] | 2019-05-14T12:07:31Z |
1707.02246
|
Data-Driven Robust Control for Type 1 Diabetes Under Meal and Exercise Uncertainties
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We present a fully closed-loop design for an artificial pancreas (AP) which regulates the delivery of insulin for the control of Type I diabetes. Our AP controller operates in a fully automated fashion, without requiring any manual interaction (e.g. in the form of meal announcements) with the patient. A major obstacle to achieving closed-loop insulin control is the uncertainty in those aspects of a patient's daily behavior that significantly affect blood glucose, especially in relation to meals and physical activity. To handle such uncertainties, we develop a data-driven robust model-predictive control framework, where we capture a wide range of individual meal and exercise patterns using uncertainty sets learned from historical data. These sets are then used in the controller and state estimator to achieve automated, precise, and personalized insulin therapy. We provide an extensive in silico evaluation of our robust AP design, demonstrating the potential of this approach, without explicit meal announcements, to support high carbohydrate disturbances and to regulate glucose levels in large clusters of virtual patients learned from population-wide survey data.
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[
"Computer Science Archive->cs.SY"
] | 2017-07-07T16:08:17Z |
2207.13081
|
Future-Dependent Value-Based Off-Policy Evaluation in POMDPs
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We study off-policy evaluation (OPE) for partially observable MDPs (POMDPs) with general function approximation. Existing methods such as sequential importance sampling estimators and fitted-Q evaluation suffer from the curse of horizon in POMDPs. To circumvent this problem, we develop a novel model-free OPE method by introducing future-dependent value functions that take future proxies as inputs. Future-dependent value functions play similar roles as classical value functions in fully-observable MDPs. We derive a new Bellman equation for future-dependent value functions as conditional moment equations that use history proxies as instrumental variables. We further propose a minimax learning method to learn future-dependent value functions using the new Bellman equation. We obtain the PAC result, which implies our OPE estimator is consistent as long as futures and histories contain sufficient information about latent states, and the Bellman completeness. Finally, we extend our methods to learning of dynamics and establish the connection between our approach and the well-known spectral learning methods in POMDPs.
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[
"Computer Science Archive->cs.LG",
"Statistics Archive->stat.ML"
] | 2022-07-26T17:53:29Z |
2204.11639
|
Investigating Black-Box Function Recognition Using Hardware Performance Counters
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This paper presents new methods and results for recognising black-box program functions using hardware performance counters (HPC), where an investigator can invoke and measure function calls. Important use cases include analysing compiled libraries, e.g. static and dynamic link libraries, and trusted execution environment (TEE) applications. We develop a generic approach to classify a comprehensive set of hardware events, e.g. branch mis-predictions and instruction retirements, to recognise standard benchmarking and cryptographic library functions. This includes various signing, verification and hash functions, and ciphers in numerous modes of operation. Three architectures are evaluated using off-the-shelf Intel/X86-64, ARM, and RISC-V CPUs. Next, we show that several known CVE-numbered OpenSSL vulnerabilities can be detected using HPC differences between patched and unpatched library versions. Further, we demonstrate that standardised cryptographic functions within ARM TrustZone TEE applications can be recognised using non-secure world HPC measurements, applying to platforms that insecurely perturb the performance monitoring unit (PMU) during TEE execution. High accuracy was achieved in all cases (86.22-99.83%) depending on the application, architectural, and compilation assumptions. Lastly, we discuss mitigations, outstanding challenges, and directions for future research.
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[
"Computer Science Archive->cs.CR"
] | 2022-04-25T13:16:33Z |
hep-ex/0308061
|
Search for light pseudoscalar sgoldstino in K- decays
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A search for the light pseudoscalar sgoldstino production in the three body K- decay K-->pipi0P has been performed with the ISTRA+ detector exposed to the 25 GeV negative secondary beam of the U70 proton synchrotron. No signal is seen. An upper limit for the branching ratio Br(K->pipi0P), at 90% confidence level, is found to be around 9*10**-6 in the effective mass m(P) range from 0 till 200 MeV, excluding the region near m(pi0) where it degrades to 3.5*10**-5.
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[
"Physics Archive->hep->hep-ex"
] | 2003-08-25T15:37:08Z |
2103.16738
|
Deciphering water-solid reactions during hydrothermal corrosion of SiC
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Water solid interfacial reactions are critical to understanding corrosion. More specifically, it is notoriously difficult to determine how water and solid interact beyond the initial chemisorption to induce the surface dissolution. Here, we report atomic-scale mechanisms of the elementary steps during SiC hydrothermal corrosion, from the initial surface attack to surface dissolution. We find that hydrogen scission reactions play a vital role in breaking Si-C bonds, regardless of the surface orientations. Stable silica layer does not form on the surface, but the newly identified chemical reactions on SiC are analogous to those observed during the dissolution of silica. SiC is dissolved directly into the water as soluble silicic acid. The rate of hydrothermal corrosion determined based on the calculated reaction activation energies is consistent with available experimental data. Our work sheds new light on understanding and interpreting the experimental observations and it provides foundation for design of materials that are resistant to corrosion in water.
|
[
"Physics Archive->cond-mat->cond-mat.mtrl-sci",
"Physics Archive->physics->physics.chem-ph"
] | 2021-03-31T00:23:35Z |
1412.3402
|
Dark Matter Deprivation in Field Elliptical Galaxy NGC 7507
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Previous studies have shown that the kinematics of the field elliptical galaxy NGC 7507 do not necessarily require dark matter. This is troubling because, in the context of LCDM cosmologies, all galaxies should have a large dark matter component. We use penalised pixel fitting software to extract velocities and velocity dispersions from GMOS slit mask spectra. Using Jeans and MONDian modelling we produce best fit models to the velocity dispersion. We find that NGC 7507 has a two component stellar halo, with the outer halo and inner haloes counter rotating. The velocity dispersion profile exhibits an increase at ~70" (~7.9 kpc), reminiscent of several other elliptical galaxies. Our best fit models are those under mild anisotropy which include ~100 times less dark matter than predicted by LCDM, although mildly anisotropic models that are completely dark matter free fit almost equally well. Our MONDian models, both isotropic and anisotropic, systematically fail to reproduce the measured velocity dispersions at almost all radii. The counter rotating outer halo implies a merger remnant, as does the increase in velocity dispersion at ~70". From simulations it seems plausible that the merger that caused the increase in velocity dispersion was a spiral-spiral merger. Our Jeans models are completely consistent with a no dark matter scenario, however, some dark matter can be accommodated, although at much lower concentrations that predicted by LCDM simulations. This indicates that NGC 7507 may be a dark matter free elliptical galaxy. Whether NGC 7507 is completely dark matter free or very dark matter poor, this is at odds with predictions from current LCDM cosmological simulations. It may be possible that the observed velocity dispersions could be reproduced if the galaxy is significantly flattened along the line of sight (e.g. due to rotation), however, invoking this flattening is problematic.
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[
"Physics Archive->astro-ph->astro-ph.GA"
] | 2014-12-10T18:39:22Z |
hep-th/9912107
|
M Theory on the Stiefel manifold and 3d Conformal Field Theories
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We compute the mass and multiplet spectrum of M theory compactified on the product of AdS(4) spacetime by the Stiefel manifold V(5,2)=SO(5)/SO(3), and we use this information to deduce via the AdS/CFT map the primary operator content of the boundary N=2 conformal field theory. We make an attempt for a candidate supersymmetric gauge theory that, at strong coupling, should be related to parallel M2-branes on the singular point of the non-compact Calabi-Yau four-fold $\sum_{a=1}^5 z_a^2 = 0$, describing the cone on V(5,2).
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[
"Physics Archive->hep->hep-th"
] | 1999-12-13T17:54:41Z |
2003.06618
|
Six dimensional ultraviolet completion of the $CP(N)$ $\sigma$ model at two loops
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We extend the recent one loop analysis of the ultraviolet completion of the $CP(N)$ nonlinear $\sigma$ model in six dimensions to two loop order in the MSbar scheme for an arbitrary covariant gauge. In particular we compute the anomalous dimensions of the fields and $\beta$-functions of the four coupling constants. We note that like Quantum Electrodynamics (QED) in four dimensions the matter field anomalous dimension only depends on the gauge parameter at one loop. As a non-trivial check we verify that the critical exponents derived from these renormalization group functions at the Wilson-Fisher fixed point are consistent with the $\epsilon$ expansion of the respective large $N$ exponents of the underlying universal theory. Using the Ward-Takahashi identity we deduce the three loop MSbar renormalization group functions for the six dimensional ultraviolet completeness of scalar QED.
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[
"Physics Archive->hep->hep-th"
] | 2020-03-14T12:30:54Z |
2104.13534
|
PAFNet: An Efficient Anchor-Free Object Detector Guidance
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Object detection is a basic but challenging task in computer vision, which plays a key role in a variety of industrial applications. However, object detectors based on deep learning usually require greater storage requirements and longer inference time, which hinders its practicality seriously. Therefore, a trade-off between effectiveness and efficiency is necessary in practical scenarios. Considering that without constraint of pre-defined anchors, anchor-free detectors can achieve acceptable accuracy and inference speed simultaneously. In this paper, we start from an anchor-free detector called TTFNet, modify the structure of TTFNet and introduce multiple existing tricks to realize effective server and mobile solutions respectively. Since all experiments in this paper are conducted based on PaddlePaddle, we call the model as PAFNet(Paddle Anchor Free Network). For server side, PAFNet can achieve a better balance between effectiveness (42.2% mAP) and efficiency (67.15 FPS) on a single V100 GPU. For moblie side, PAFNet-lite can achieve a better accuracy of (23.9% mAP) and 26.00 ms on Kirin 990 ARM CPU, outperforming the existing state-of-the-art anchor-free detectors by significant margins. Source code is at https://github.com/PaddlePaddle/PaddleDetection.
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[
"Computer Science Archive->cs.CV"
] | 2021-04-28T02:32:54Z |
1503.07223
|
On the Seifert fibered space link group
|
We introduce generalized arrow diagrams and generalized Reidemeister moves for diagrams of links in Seifert fibered spaces. We give a presentation of the fundamental group of the link complement. As a corollary we are able to compute the first homology group of the complement and the twisted Alexander polynomials of the link.
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[
"Mathematics Archive->math.GT"
] | 2015-03-24T22:47:33Z |
0910.2879
|
Single vortex structure in two models of iron pnictide $s^\pm$ superconductivity
|
The structure of a single vortex in a FeAs superconductor is studied in the framework of two formulations of superconductivity for the recently proposed sign-reversed $s$ wave ($s^\pm$) scenario: {\it (i)} a continuum model taking into account the existence of an electron and a hole band with a repulsive local interaction between the two; {\it (ii)} a lattice tight-binding model with two orbitals per unit cell and a next-nearest-neighbour attractive interaction. In the first model, the local density of states (LDOS) at the vortex centre, as a function of energy, exhibits a peak at the Fermi level, while in the second model such LDOS peak is deviated from the Fermi level and its energy depends on band filling. An impurity located outside the vortex core has little effect on the LDOS peak, but an impurity close to the vortex core can almost suppress it and modify its position.
|
[
"Physics Archive->cond-mat->cond-mat.supr-con"
] | 2009-10-15T14:03:19Z |
2305.14146
|
Industry Practices for Challenging Autonomous Driving Systems with Critical Scenarios
|
Testing autonomous driving systems for safety and reliability is extremely complex. A primary challenge is identifying the relevant test scenarios, especially the critical ones that may expose hazards or risks of harm to autonomous vehicles and other road users. There are several proposed methods and tools for critical scenario identification, while the industry practices, such as the selection, implementation, and limitations of the approaches, are not well understood. In this study, we conducted 10 interviews with 13 interviewees from 7 companies in autonomous driving in Sweden. We used thematic modeling to analyse and synthesize the interview data. We found there are little joint efforts in the industry to explore different approaches and tools, and every approach has its own limitations and weaknesses. To that end, we recommend combining different approaches available, collaborating among different stakeholders, and continuously learning the field of critical scenario identification and testing. The contributions of our study are the exploration and synthesis of the industry practices and related challenges for critical scenario identification and testing, and the potential increase of the industry relevance for future studies in related topics.
|
[
"Computer Science Archive->cs.SE"
] | 2023-05-23T15:13:11Z |
physics/0703025
|
A Bright, Guided Molecular Beam With Hydrodynamic Enhancement
|
We realize a novel high flux source of cold atoms and molecules employing hydrodynamic enhancement of an effusive aperture at cryogenic temperatures. Molecular oxygen from the source is coupled to a magnetic guide, delivering a cold, continuous, guided flux of 3e12 oxygen molecules per second, with a molecule temperature of a few kelvin. The dynamics of the source are studied by creating and spectroscopically analyzing high-flux beams of atomic ytterbium.
|
[
"Physics Archive->physics->physics.chem-ph"
] | 2007-03-02T19:01:35Z |
1809.10050
|
An Iterative Regularized Incremental Projected Subgradient Method for a Class of Bilevel Optimization Problems
|
We study a class of bilevel convex optimization problems where the goal is to find the minimizer of an objective function in the upper level, among the set of all optimal solutions of an optimization problem in the lower level. A wide range of problems in convex optimization can be formulated using this class. An important example is the case where an optimization problem is ill-posed. In this paper, our interest lies in addressing the bilevel problems, where the lower level objective is given as a finite sum of separate nondifferentiable convex component functions. This is the case in a variety of applications in distributed optimization, such as large-scale data processing in machine learning and neural networks. To the best of our knowledge, this class of bilevel problems, with a finite sum in the lower level, has not been addressed before. Motivated by this gap, we develop an iterative regularized incremental subgradient method, where the agents update their iterates in a cyclic manner using a regularized subgradient. Under a suitable choice of the regularization parameter sequence, we establish the convergence of the proposed algorithm and derive a rate of $\mathcal{O} \left({1}/k^{0.5-\epsilon}\right)$ in terms of the lower level objective function for an arbitrary small $\epsilon>0$. We present the performance of the algorithm on a binary text classification problem.
|
[
"Mathematics Archive->math.OC"
] | 2018-09-26T15:09:17Z |
2104.04064
|
Many-Joint Robot Arm Control with Recurrent Spiking Neural Networks
|
In the paper, we show how scalable, low-cost trunk-like robotic arms can be constructed using only basic 3D-printing equipment and simple electronics. The design is based on uniform, stackable joint modules with three degrees of freedom each. Moreover, we present an approach for controlling these robots with recurrent spiking neural networks. At first, a spiking forward model learns motor-pose correlations from movement observations. After training, intentions can be projected back through unrolled spike trains of the forward model essentially routing the intention-driven motor gradients towards the respective joints, which unfolds goal-direction navigation. We demonstrate that spiking neural networks can thus effectively control trunk-like robotic arms with up to 75 articulated degrees of freedom with near millimeter accuracy.
|
[
"Computer Science Archive->cs.RO"
] | 2021-04-08T21:09:10Z |
cond-mat/0604602
|
Ginsburg-Landau theory of supersolid
|
We develop a simple Ginsburg-Landau theory to study all the possible phases and phase transitions in $^{4}He $, analyze the condition for the existence of the supersolid (SS) and map out its global phase diagram from a unified framework. If the condition favors the existence of the SS, we use the GL theory to address several experimental facts and also make some predictions that are amenable to experimental tests. A key prediction is that the X-ray scattering intensity from the SS ought to have an additional modulation over that of the NS. The modulation amplitude is proportional to the Non-Classical Rotational-Inertial (NCRI) observed in the torsional oscillator experiments.
|
[
"Physics Archive->cond-mat->cond-mat.str-el",
"Physics Archive->cond-mat->cond-mat.supr-con"
] | 2006-04-27T17:35:58Z |
0912.2335
|
Radio Sources from a 31 GHz Sky Survey with the Sunyaev-Zel'dovich Array
|
We present the first sample of 31-GHz selected sources to flux levels of 1 mJy. From late 2005 to mid 2007, the Sunyaev-Zel'dovich Array (SZA) observed 7.7 square degrees of the sky at 31 GHz to a median rms of 0.18 mJy/beam. We identify 209 sources at greater than 5 sigma significance in the 31 GHz maps, ranging in flux from 0.7 mJy to ~200 mJy. Archival NVSS data at 1.4 GHz and observations at 5 GHz with the Very Large Array are used to characterize the sources. We determine the maximum-likelihood integrated source count to be N(>S) = (27.2 +- 2.5) deg^-2 x (S_mJy)^(-1.18 +- 0.12) over the flux range 0.7 - 15 mJy. This result is significantly higher than predictions based on 1.4-GHz selected samples, a discrepancy which can be explained by a small shift in the spectral index distribution for faint 1.4-GHz sources. From comparison with previous measurements of sources within the central arcminute of massive clusters, we derive an overdensity of 6.8 +- 4.4, relative to field sources.
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[
"Physics Archive->astro-ph->astro-ph.CO"
] | 2009-12-11T20:38:53Z |
1711.04425
|
Message Passing Stein Variational Gradient Descent
|
Stein variational gradient descent (SVGD) is a recently proposed particle-based Bayesian inference method, which has attracted a lot of interest due to its remarkable approximation ability and particle efficiency compared to traditional variational inference and Markov Chain Monte Carlo methods. However, we observed that particles of SVGD tend to collapse to modes of the target distribution, and this particle degeneracy phenomenon becomes more severe with higher dimensions. Our theoretical analysis finds out that there exists a negative correlation between the dimensionality and the repulsive force of SVGD which should be blamed for this phenomenon. We propose Message Passing SVGD (MP-SVGD) to solve this problem. By leveraging the conditional independence structure of probabilistic graphical models (PGMs), MP-SVGD converts the original high-dimensional global inference problem into a set of local ones over the Markov blanket with lower dimensions. Experimental results show its advantages of preventing vanishing repulsive force in high-dimensional space over SVGD, and its particle efficiency and approximation flexibility over other inference methods on graphical models.
|
[
"Statistics Archive->stat.ML"
] | 2017-11-13T05:39:25Z |
astro-ph/0701247
|
Spectral Running and Non-Gaussianity from Slow-Roll Inflation in Generalised Two--Field Models
|
Theories beyond the standard model such as string theory motivate low energy effective field theories with several scalar fields which are not only coupled through a potential but also through their kinetic terms. For such theories we derive the general formulae for the running of the spectral indices for the adiabatic, isocurvature and correlation spectra in the case of two field inflation. We also compute the expected non-Gaussianity in such models for specific forms of the potentials. We find that the coupling has little impact on the level of non-Gaussianity during inflation.
|
[
"Physics Archive->astro-ph"
] | 2007-01-09T19:08:57Z |
1408.3496
|
Almost-Fisher families
|
A classic theorem in combinatorial design theory is Fisher's inequality, which states that a family $\mathcal F$ of subsets of $[n]$ with all pairwise intersections of size $\lambda$ can have at most $n$ non-empty sets. One may weaken the condition by requiring that for every set in $\mathcal F$, all but at most $k$ of its pairwise intersections have size $\lambda$. We call such families $k$-almost $\lambda$-Fisher. Vu was the first to study the maximum size of such families, proving that for $k=1$ the largest family has $2n-2$ sets, and characterising when equality is attained. We substantially refine his result, showing how the size of the maximum family depends on $\lambda$. In particular we prove that for small $\lambda$ one essentially recovers Fisher's bound. We also solve the next open case of $k=2$ and obtain the first non-trivial upper bound for general $k$.
|
[
"Mathematics Archive->math.CO"
] | 2014-08-15T08:39:00Z |
cs/0509091
|
Minimum Cost Homomorphisms to Semicomplete Multipartite Digraphs
|
For digraphs $D$ and $H$, a mapping $f: V(D)\dom V(H)$ is a {\em homomorphism of $D$ to $H$} if $uv\in A(D)$ implies $f(u)f(v)\in A(H).$ For a fixed directed or undirected graph $H$ and an input graph $D$, the problem of verifying whether there exists a homomorphism of $D$ to $H$ has been studied in a large number of papers. We study an optimization version of this decision problem. Our optimization problem is motivated by a real-world problem in defence logistics and was introduced very recently by the authors and M. Tso. Suppose we are given a pair of digraphs $D,H$ and a positive integral cost $c_i(u)$ for each $u\in V(D)$ and $i\in V(H)$. The cost of a homomorphism $f$ of $D$ to $H$ is $\sum_{u\in V(D)}c_{f(u)}(u)$. Let $H$ be a fixed digraph. The minimum cost homomorphism problem for $H$, MinHOMP($H$), is stated as follows: For input digraph $D$ and costs $c_i(u)$ for each $u\in V(D)$ and $i\in V(H)$, verify whether there is a homomorphism of $D$ to $H$ and, if it does exist, find such a homomorphism of minimum cost. In our previous paper we obtained a dichotomy classification of the time complexity of \MiP for $H$ being a semicomplete digraph. In this paper we extend the classification to semicomplete $k$-partite digraphs, $k\ge 3$, and obtain such a classification for bipartite tournaments.
|
[
"Computer Science Archive->cs.DM"
] | 2005-09-28T15:40:50Z |
2004.07189
|
Existence issues for a large class of degenerate elliptic equations with nonlinear Hamiltonians
|
We give sufficient conditions for the existence and uniqueness, in bounded uniformly convex domains $\Omega$, of solutions of degenerate elliptic equations depending also on the nonlinear gradient term $H$, in term of the size of $\Omega$, of the forcing term $f$ and of $H$. The results apply to a wide class of equations, having as principal part significant examples, e.g. linear degenerate operators, weighted partial trace operators and the homogeneous Monge-Amp\`ere operator.
|
[
"Mathematics Archive->math.AP"
] | 2020-04-15T16:35:00Z |
2304.05063
|
Do conformational changes contribute to the surface plasmon resonance signal?
|
Surface plasmon resonance (SPR)-based biosensors are widely used instruments for characterizing molecular interactions. In theory the SPR signal depends only on mass changes for interacting molecules of same chemical nature. Whether conformational changes of interacting molecules also contribute to the SPR signal is still a subject of lively debates. Works have been published claiming that conformational changes were detected but all factors contributing to the SPR signal were not carefully considered, in addition to often using no or improper controls. In the present work we used a very well-characterized oligonucleotide, the thrombin-binding DNA aptamer (TBA), which upon binding of potassium ions folds into a two G-tetrad antiparallel G-quadruplex structure. All terms contributing to the maximal expected SPR response, Rmax, in particular the refractive index increment, RII, of both partners and the fraction of immobilized TBA target available, ca, were experimentally assessed. The resulting Rmax was then compared to the maximal experimental SPR response for potassium ions binding to TBA using appropriate controls. Regardless how the RIIs were measured, by SPR or refractometry, and how much TBA available for interacting with potassium ions was considered, the theoretical and the experimental SPR responses never matched, the former being always lower than the latter. Using a straightforward experimental model system and by thoroughly taking into account all contributing factors we therefore conclude that conformational changes can indeed contribute to the measured SPR signal.
|
[
"Quantitative Biology Archive->q-bio.BM"
] | 2023-04-11T08:51:34Z |
1402.2546
|
The Sasaki Join, Hamiltonian 2-forms, and Constant Scalar Curvature
|
We describe a general procedure for constructing new Sasaki metrics of constant scalar curvature from old ones. Explicitly, we begin with a regular Sasaki metric of constant scalar curvature on a 2n+1-dimensional compact manifold M and construct a sequence, depending on four integer parameters, of rays of constant scalar curvature (CSC) Sasaki metrics on a compact Sasaki manifold of dimension $2n+3$. We also give examples which show that the CSC rays are often not unique on a fixed strictly pseudoconvex CR manifold or a fixed contact manifold. Moreover, it is shown that when the first Chern class of the contact bundle vanishes, there is a two dimensional subcone of Sasaki Ricci solitons in the Sasaki cone, and a unique Sasaki-Einstein metric in each of the two dimensional sub cones.
|
[
"Mathematics Archive->math.DG"
] | 2014-02-11T16:17:58Z |
1411.4964
|
$B^0_{s} \rightarrow \mu^+\mu^-$ at LHC
|
Rare leptonic decays of $B_{(s)}^0$ mesons are sensitive probes of New Physics effects. A combination of the CMS and LHCb analyses on the search of the rare decays $B_{s}^0 \rightarrow \mu^+\mu^-$ and $B^0 \rightarrow \mu^+\mu^-$ is presented. The branching fractions of $B_{s}^0 \rightarrow \mu^+\mu^-$ and $B^0 \rightarrow \mu^+\mu^-$ are measured to be $\mathcal{B}(B_{s}^0 \rightarrow \mu^+\mu^-) = (2.8 \,^{+0.7}_{-0.6}) \times 10^{-9}$ and $\mathcal{B}(B^0 \rightarrow \mu^+\mu^-) = (3.9 \,^{+1.6}_{-1.4}) \times 10^{-10}$ respectively. A statistical significances of $6.2\,\sigma$ is evaluated for $B_{s}^0 \rightarrow \mu^+\mu^-$ from the Wilks' theorem while a significance of $3.0\, \sigma$ is measured for $B^0 \rightarrow \mu^+\mu^-$ from the Feldman-Cousins procedure.
|
[
"Physics Archive->hep->hep-ex"
] | 2014-11-18T19:04:15Z |
2106.09089
|
Moving Quantum States without SWAP via Intermediate Higher Dimensional Qudits
|
Quantum algorithms can be realized in the form of a quantum circuit. To map quantum circuit for specific quantum algorithm to quantum hardware, qubit mapping is an imperative technique based on the qubit topology. Due to the neighbourhood constraint of qubit topology, the implementation of quantum algorithm rightly, is essential for moving information around in a quantum computer. Swapping of qubits using SWAP gate moves the quantum state between two qubits and solves the neighbourhood constraint of qubit topology. Though, one needs to decompose the SWAP gate into three CNOT gates to implement SWAP gate efficiently, but unwillingly quantum cost with respect to gate count and depth increases. In this paper, a new formalism of moving quantum states without using SWAP operation is introduced for the first time to the best of our knowledge. Moving quantum states through qubits have been attained with the adoption of temporary intermediate qudit states. This introduction of intermediate qudit states has exhibited a three times reduction in quantum cost with respect to gate count and approximately two times reduction in respect to circuit depth compared to the state-of-the-art approach of SWAP gate insertion. Further, the proposed approach is generalized to any dimensional quantum system.
|
[
"Physics Archive->quant-ph"
] | 2021-06-16T19:21:53Z |
gr-qc/0305060
|
Future complete Einsteinian space times with U(1) symmetry, the unpolarized case
|
I prove the existence of vacuum $S^{1}$ symmetric Einsteinian, unpolarized, space times which are complete in the direction of the expansion, for small initial data, without supposing that the $S^{1}$ orbits are orthogonal to the 3-manifolds, as was done in previous work in collaboration with V. Moncrief.
|
[
"Physics Archive->gr-qc"
] | 2003-05-15T19:49:43Z |
nucl-th/9304017
|
Quasielastic neutrino scattering from oxygen and the atmospheric neutrino problem
|
We examine several phenomena beyond the scope of Fermi-gas models that affect the quasielastic scattering (from oxygen) of neutrinos in the 0.1 -- 3.0 GeV range. These include Coulomb interactions of outgoing protons and leptons, a realistic finite-volume mean field, and the residual nucleon-nucleon interaction. None of these effects are accurately represented in the Monte Carlo simulations used to predict event rates due to $\mu$ and $e$ neutrinos from cosmic-ray collisions in the atmosphere. We nevertheless conclude that the neglected physics cannot account for the anomalous $\mu$ to $e$ ratio observed at Kamiokande and IMB, and is unlikely to change absolute event rates by more than 10--15\%. We briefly mention other phenomena, still to be investigated in detail, that may produce larger changes.
|
[
"Physics Archive->hep->hep-ph",
"Physics Archive->nucl->nucl-th"
] | 1993-04-22T21:13:58Z |
2310.13609
|
Statistical and dynamical properties of polarised crowd
|
We present a minimal computational model to mimic the crowd in marathon race. We aim to examine the influence of frontliners on crowd dynamics by comparing the simulated races with and without their presence. The primary outcome of our study revealed that the local velocity and density of the participants exhibit a wave pattern similar to what is observed in actual races. Another important result we obtained is that the travelling wave in the crowd consistently propagates with a constant speed, irrespective of the system size under consideration. The dynamic of participants in the longitudinal direction mainly contributes for the velocity fluctuation and the fluctuation in the transverse direction is suppressed. In the absence of frontliners, the fluctuations in density and velocity weakens without significantly influencing the other statistical and dynamical characteristics of the crowd. It is also observed that the density wave travels faster than the velocity wave. Through this research, we aim to enhance our understanding of crowd motion, which can inform the development of effective crowd management strategies and contribute to the successful control of such events.
|
[
"Physics Archive->cond-mat->cond-mat.soft",
"Physics Archive->cond-mat->cond-mat.stat-mech"
] | 2023-10-20T15:59:54Z |
1904.00446
|
Interpretation of the Narrow $J/\psi p$ Peaks in $\Lambda_b \to J/\psi p K^-$ Decay in the Compact Diquark Model
|
Recently, the LHCb Collaboration have updated their analysis of the resonant $J/\psi p$ mass spectrum in the decay $\Lambda_b^0 \to J/\psi p K^-$. In the combined Run~1 and Run~2 LHCb data, three peaks are observed, with the former $P_c(4450)^+$ state split into two narrow states, $P_c(4440)^+$ and $P_c(4457)^+$, having the masses $M=(4440.3\pm 1.3^{+4.1}_{-4.7})$ MeV and $M=(4457.3\pm 0.6^{+4.1}_{-1.7})$ MeV, and decay widths $\Gamma=(20.6\pm 4.9^{+8.7}_{-10.1})$ MeV and $\Gamma=(6.4\pm 2.0^{+5.7}_{-1.9})$ MeV, respectively. In addition, a third narrow peak, $P_c(4312)^+$, having the mass $M=(4311.9\pm 0.7^{+6.8}_{-0.6})$ MeV and decay width $\Gamma=(9.8\pm 2.7^{+3.7}_{-4.5})$ MeV is also observed. The LHCb analysis is not sensitive to broad $J/\psi p$ contributions like the former $P_c(4380)^+$, implying that there could be more states present in the data. Also the spin-parity, $J^P$, assignments of the states are not yet determined. We interpret these resonances in the compact diquark model as hidden-charm diquark-diquark-antiquark baryons, having the following spin and angular momentum quantum numbers: $P_c(4312)^+ =\{\bar c [cu]_{s=1} [ud]_{s=0}; L_P=0, J^P=3/2^-\}$, the $S$-wave state, and the other two as $P$-wave states, with $P_c(4440)^+ =\{\bar c [cu]_{s=1} [ud]_{s=0}; L_P=1, J^P=3/2^+\}$ and $P_c(4457)^+ = \{\bar c [cu]_{s=1} [ud]_{s=0}; L_P=1, J^P=5/2^+ \}$. The subscripts denote the spins of the diquarks and $L_P=0,1$ is the orbital angular momentum quantum number of the pentaquark. These assignments are in accord with the heavy-quark-symmetry selection rules for $\Lambda_b$-baryon decays, in which the spin $S=0$ of the light diquark $[ud]_{s=0}$ is conserved. The masses of observed states can be accommodated in this framework and the two heaviest states have the positive parities as opposed to the molecular-like interpretations.
|
[
"Physics Archive->hep->hep-ex",
"Physics Archive->hep->hep-ph"
] | 2019-03-31T16:58:04Z |
0809.2744
|
A simple model for NN correlations in quasielastic lepton-nucleus scattering
|
We present a covariant extension of the relativistic Fermi gas model which incorporates correlation effects in nuclei. Within this model, inspired by the BCS descriptions of systems of fermions, we obtain the nuclear spectral function and from it the superscaling function for use in treating high-energy quasielastic electroweak processes. Interestingly, this model has the capability to yield the asymmetric tail seen in the experimental scaling function.
|
[
"Physics Archive->hep->hep-ph",
"Physics Archive->nucl->nucl-th"
] | 2008-09-16T15:44:36Z |
2201.06500
|
Growing Neural Network with Shared Parameter
|
We propose a general method for growing neural network with shared parameter by matching trained network to new input. By leveraging Hoeffding's inequality, we provide a theoretical base for improving performance by adding subnetwork to existing network. With the theoretical base of adding new subnetwork, we implement a matching method to apply trained subnetwork of existing network to new input. Our method has shown the ability to improve performance with higher parameter efficiency. It can also be applied to trans-task case and realize transfer learning by changing the combination of subnetworks without training on new task.
|
[
"Computer Science Archive->cs.AI",
"Computer Science Archive->cs.LG"
] | 2022-01-17T16:24:17Z |
2006.10393
|
A general relation between stacking order and Chern index: a topological map of minimally twisted bilayer graphene
|
We derive a general relation between the stacking vector ${\bf u}$ describing the relative shift of two layers of bilayer graphene and the Chern index. We find $C = \nu - \text{sign}\left(|V_{AB}|-|V_{BA}|\right)$, where $\nu$ is a valley index and $|V_{\alpha\beta}|$ the absolute value of stacking potentials that depend on ${\bf u}$ and that uniquely determine the interlayer interaction; AA stacking plays no role in the topological character. With this expression we show that while ideal and relaxed minimally twisted bilayer graphene appear so distinct as to be almost different materials, their Chern index maps are, remarkably, identical. The topological physics of this material is thus strongly robust to lattice relaxations.
|
[
"Physics Archive->cond-mat->cond-mat.mes-hall",
"Physics Archive->cond-mat->cond-mat.mtrl-sci"
] | 2020-06-18T09:54:14Z |
1710.01164
|
A partition function for Schwarzschild-AdS and Kerr-AdS black holes and for quantized globally hyperbolic spacetimes with a negative cosmological constant
|
We apply quantum statistics to our quantized versions of Schwarzschild-AdS and Kerr-AdS black holes and also to the quantized globally hyperbolic spacetimes having an asymptotically Euclidean Cauchy hypersurface by first proving, for the temporal Hamiltonian $H_0$, that $e^{-\beta H_0}$, $\beta>0$, is of trace class and then, that this result is also valid for the spatial Hamiltonian $H_1$, which has the same eigenvalues but with larger multiplicities. Since the lowest eigenvalue is strictly positive the extension of $e^{-\beta H_1}$ to the corresponding symmetric Fock space is also of trace class and we are thus able to define a partition function $Z$, the operator density $\rho$, the entropy $S$, and the average energy $E$. We prove that $S$ and $E$ tend to infinity if the cosmological constant $\Lambda$ tends to $0$ and vanish if $|\Lambda|$ tends to infinity. We also conjecture that $E$ is the source of the dark matter and that the dark energy density is a multiple of the eigenvalue of $\rho$ with respect to the vacuum vector which is $Z^{-1}$.
|
[
"Physics Archive->physics->physics.gen-ph"
] | 2017-10-03T14:17:37Z |
cond-mat/0612026
|
New Type Phase Transition of Li2RuO3 with Honeycomb Structure
|
A new-type structural transition has been found in Li2RuO3 with honeycomb lattice of edge-sharing RuO6-octahedra. With decreasing temperature T, the electrical resistivity exhibits an anomalous increase at T=Tc~540 K, suggesting the (metal to insulator)-like transition and the magnetic susceptibility also shows a sharp decrease. Detailed structure analyses have revealed that the high temperature space group C2/m changes to P21/m at Tc. The most striking fact is that a significant reduction of the bond lengths is found between two of six Ru-Ru pairs of the hexagon in the low temperature phase, indicating a new type phase transition by the mechanism of the formation of molecular orbits of these Ru-Ru pairs.
|
[
"Physics Archive->cond-mat->cond-mat.mtrl-sci",
"Physics Archive->cond-mat->cond-mat.str-el"
] | 2006-12-01T11:58:56Z |
1710.00604
|
Safe Local Exploration for Replanning in Cluttered Unknown Environments for Micro-Aerial Vehicles
|
In order to enable Micro-Aerial Vehicles (MAVs) to assist in complex, unknown, unstructured environments, they must be able to navigate with guaranteed safety, even when faced with a cluttered environment they have no prior knowledge of. While trajectory optimization-based local planners have been shown to perform well in these cases, prior work either does not address how to deal with local minima in the optimization problem, or solves it by using an optimistic global planner. We present a conservative trajectory optimization-based local planner, coupled with a local exploration strategy that selects intermediate goals. We perform extensive simulations to show that this system performs better than the standard approach of using an optimistic global planner, and also outperforms doing a single exploration step when the local planner is stuck. The method is validated through experiments in a variety of highly cluttered environments including a dense forest. These experiments show the complete system running in real time fully onboard an MAV, mapping and replanning at 4 Hz.
|
[
"Computer Science Archive->cs.RO"
] | 2017-10-02T12:19:35Z |
1110.1593
|
Microscopic derivation of two-component Ginzburg-Landau model and conditions of its applicability in two-band systems
|
We report a microscopic derivation of two-component Ginzburg-Landau (GL) field theory and the conditions of its validity in two-band superconductors. We also investigate the conditions when microscopically derived or phenomenological GL models fail and one should resort to a microscopic description. We show that besides being directly applicable at elevated temperatures, a version of a minimal two-component GL theory in certain cases also gives accurate description of certain aspects of a two-band system even substantially far from $T_c$. This shows that two-component GL model can be used for addressing a wide range of questions in multiband systems, in particular vortex physics and magnetic response. We also argue that single Ginzburg-Landau parameter cannot in general characterize magnetic response of multiband systems.
|
[
"Physics Archive->cond-mat->cond-mat.supr-con"
] | 2011-10-07T17:47:33Z |
1804.01306
|
A Unifying Contrast Maximization Framework for Event Cameras, with Applications to Motion, Depth, and Optical Flow Estimation
|
We present a unifying framework to solve several computer vision problems with event cameras: motion, depth and optical flow estimation. The main idea of our framework is to find the point trajectories on the image plane that are best aligned with the event data by maximizing an objective function: the contrast of an image of warped events. Our method implicitly handles data association between the events, and therefore, does not rely on additional appearance information about the scene. In addition to accurately recovering the motion parameters of the problem, our framework produces motion-corrected edge-like images with high dynamic range that can be used for further scene analysis. The proposed method is not only simple, but more importantly, it is, to the best of our knowledge, the first method that can be successfully applied to such a diverse set of important vision tasks with event cameras.
|
[
"Computer Science Archive->cs.CV",
"Computer Science Archive->cs.RO"
] | 2018-04-04T08:59:57Z |
1409.5809
|
Status and Opportunities at Project X: A Multi-MW Facility for Intensity Frontier Research
|
Project X is a multi-megawatt proton facility being developed to support a world-leading program in Intensity Frontier physics at Fermilab. The facility will support programs in elementary particle and nuclear physics, with the potential for broader applications in materials and energy research. Project X is in the development stage with a R&D program focused on front end and superconducting RF acceleration technologies, and with design concepts for a staged implementation. This paper will review the status of the Project X conceptual development and the associated R&D programs.
|
[
"Physics Archive->physics->physics.acc-ph"
] | 2014-09-19T20:30:18Z |
0911.1639
|
Black Hole Outflows
|
I show that Eddington accretion episodes in AGN are likely to produce winds with velocities $v \sim 0.1c$ and ionization parameters up to $\xi \sim 10^4$ (cgs), implying the presence of resonance lines of helium-- and hydrogenlike iron. These properties are direct consequences of momentum and mass conservation respectively, and agree with recent X-ray observations of fast outflows from AGN. Because the wind is significantly subluminal, it can persist long after the AGN is observed to have become sub--Eddington. The wind creates a strong cooling shock as it interacts with the interstellar medium of the host galaxy, and this cooling region may be observable in an inverse Compton continuum and lower--excitation emission lines associated with lower velocities. The shell of matter swept up by the (`momentum--driven') shocked wind must propagate beyond the black hole's sphere of influence on a timescale $\la 3\times 10^5$ yr. Outside this radius the shell stalls unless the black hole mass has reached the value $M_{\sigma}$ implied by the $M - \sigma$ relation. If the wind shock did not cool, as suggested here, the resulting (`energy--driven') outflow would imply a far smaller SMBH mass than actually observed. In galaxies with large bulges the black hole may grow somewhat beyond this value, suggesting that the observed $M -\sigma$ relation may curve upwards at large $M$. Minor accretion events with small gas fractions can produce galaxy--wide outflows with velocities significantly exceeding $\sigma$, including fossil outflows in galaxies where there is little current AGN activity. Some rare cases may reveal the energy--driven outflows which sweep gas out of the galaxy and establish the black hole--bulge mass relation. However these require the quasar to be at the Eddington luminosity.
|
[
"Physics Archive->astro-ph->astro-ph.CO"
] | 2009-11-09T11:24:58Z |
2204.11418
|
Riemannian Hamiltonian methods for min-max optimization on manifolds
|
In this paper, we study min-max optimization problems on Riemannian manifolds. We introduce a Riemannian Hamiltonian function, minimization of which serves as a proxy for solving the original min-max problems. Under the Riemannian Polyak--{\L}ojasiewicz condition on the Hamiltonian function, its minimizer corresponds to the desired min-max saddle point. We also provide cases where this condition is satisfied. For geodesic-bilinear optimization in particular, solving the proxy problem leads to the correct search direction towards global optimality, which becomes challenging with the min-max formulation. To minimize the Hamiltonian function, we propose Riemannian Hamiltonian methods (RHM) and present their convergence analyses. We extend RHM to include consensus regularization and to the stochastic setting. We illustrate the efficacy of the proposed RHM in applications such as subspace robust Wasserstein distance, robust training of neural networks, and generative adversarial networks.
|
[
"Computer Science Archive->cs.LG",
"Mathematics Archive->math.OC",
"Statistics Archive->stat.ML"
] | 2022-04-25T03:32:17Z |
1807.11267
|
Coherent Explicit Dictionary Application for Haskell: Formalisation and Coherence Proof
|
Type classes are one of Haskell's most popular features and extend its type system with ad-hoc polymorphism. Since their conception, there were useful features that could not be offered because of the desire to offer two correctness properties: coherence and global uniqueness of instances. Coherence essentially guarantees that program semantics are independent from type-checker internals. Global uniqueness of instances is relied upon by libraries for enforcing, for example, that a single order relation is used for all manipulations of an ordered binary tree. The features that could not be offered include explicit dictionary application and local instances, which would be highly useful in practice. We propose a new design for offering explicit dictionary application, without compromising coherence and global uniqueness. We introduce a novel criterion based on GHC's type argument roles to decide when a dictionary application is safe with respect to global uniqueness of instances. We preserve coherence by detecting potential sources of incoherence, and prove it formally. Moreover, our solution makes it possible to use local dictionaries. In addition to developing our ideas formally, we have implemented a working prototype in GHC. This report contains the full formalisation and coherence proof.
|
[
"Computer Science Archive->cs.PL"
] | 2018-07-30T10:07:19Z |
2212.12755
|
Coherent states with minimum Gini uncertainty for finite quantum systems
|
Uncertainty relations $\Delta(\rho)\ge \eta_d$ in terms of the Gini index are studied. The `Gini uncertainty constant' $\eta_d$ is estimated numerically and compared to an upper bound $\tilde \eta_d\ge \eta_d$. It is shown that for large $d$ we get $\tilde \eta_d\approx \eta_d$. States $\ket{g}$ with minimum Gini uncertainty and displacement transformations are used to define coherent states $\ket{\alpha, \beta}_g$ (where $\alpha, \beta \in {\mathbb Z}_d$) with minimum Gini uncertainty ($\Delta[\ket{\alpha, \beta}_g\;_g\bra{\alpha, \beta}]\approx \eta_d$). The $\ket{\alpha, \beta}_g$ resolve the identity, and therefore an arbitrary state can be expanded in terms of them. This expansion is robust in the presence of noise.
|
[
"Physics Archive->quant-ph"
] | 2022-12-24T15:34:42Z |
hep-ph/9411259
|
The $\pi\pi$ Amplitude in Generalized Chiral Perturbation Theory
|
The $\pi\pi$ interaction is studied at one loop order in the framework of Generalized Chiral Perturbation theory
|
[
"Physics Archive->hep->hep-ph"
] | 1994-11-10T09:49:35Z |
1610.02764
|
Controllable deposition of titanium dioxides onto carbon nanotubes in aqueous solutions
|
Within the field of nanotechnology, nano-scale composites have significant potential in the development of advanced materials for functional applications. Here, composites based on carbon nanotubes and titanium dioxides have been prepared with titanyl sulfate using a chemical bath deposition method at or near room temperature. Two kinds of titanium dioxide depositions corresponding to rutile and anatase were sheathed on carbon nanotubes evenly by adjusting the precursor concentration and temperature. Possible composite mechanisms are discussed. Compared with original tubes, the specific surface areas have been improved nearly four times and the content ratio of mesostructures has also been increased after deposition processes.
|
[
"Physics Archive->cond-mat->cond-mat.mtrl-sci"
] | 2016-10-10T03:22:33Z |
1107.5489
|
Pseudotensor mesons as three-body resonances
|
We show that the lightest pseudotensor mesons J^{PC}=2^-+ can be regarded as molecules made of a pseudoscalar (P) 0^-+ and a tensor 2^++ meson, where the latter is itself made of two vector (V) mesons. The idea stems from the fact that the vector-vector interaction in s-wave and spin 2 is very strong, to the point of generating the 2^++ tensor mesons. On the other hand the interaction of a pseudoscalar with a vector meson in s-wave is also very strong and it generates dynamically the lightest axial-vector mesons. Therefore we expect the PVV interaction to be strongly attractive and thus able to build up quasibound PVV resonances. We calculate the three body PVV interaction by using the fixed center approximation to the Faddeev equations where the two vectors are clustered forming a tensor meson. We find clear resonant structures which can be identified with the pi_2(1670), eta_2(1645) and K^*_2(1770) (2^-+) pseudotensor mesons.
|
[
"Physics Archive->hep->hep-ph"
] | 2011-07-27T14:29:03Z |
2010.11777
|
Synthesis and physical properties of perovskite Sm$_{1-x}$Sr$_x$NiO$_3$ (x = 0, 0.2) and infinite-layer Sm$_{0.8}$Sr$_{0.2}$NiO$_2$ nickelates
|
Recently, superconductivity at about 9-15K was discovered in Nd$_{1-x}$Sr$_x$NiO$_2$ infinite-layer thin films, which has stimulated enormous interests in related rare-earth nickelates. Usually, the first step to synthesize this 112 phase is to fabricate the RNiO$_3$ phase, however, it was reported that the 113 phase is very difficult to be synthesized successfully due to the formation of unusual Ni$^{3+}$ oxidation state. And the difficulty of preparation is enhanced as the ionic radius of rare-earth element decreases. In this work, we report the synthesis and investigation on multiple physical properties of polycrystalline perovskites Sm$_{1-x}$Sr$_x$NiO$_3$ (x = 0, 0.2) in which the ionic radius of Sm$^{3+}$ is smaller than that of Pr$^{3+}$ and Nd$^{3+}$ in related superconducting thin films. The structural and compositional analyses conducted by X-ray diffraction and energy dispersive X-ray spectrum reveal that the samples mainly contain the perovskite phase of Sm$_{1-x}$Sr$_x$NiO$_3$ with small amount of NiO impurities. Magnetization and resistivity measurements indicate that the parent phase SmNiO$_3$ undergoes a paramagnetic-antiferromagnetic transition at about 224K on a global insulating background. In contrast, the Sr-doped sample Sm$_{0.8}$Sr$_{0.2}$NiO$_3$ shows a metallic behavior from 300K down to about 12K, while below 12K the resistivity exhibits a slight logarithmic increase. Meanwhile, from the magnetization curves, we can see that a possible spin-glass state occurs below 12K in Sm$_{0.8}$Sr$_{0.2}$NiO$_3$. Using a soft chemical reduction method, we also obtain the infinite-layer phase Sm$_{0.8}$Sr$_{0.2}$NiO$_2$ with square NiO$_2$ planes. The compound shows an insulating behavior which can be described by the three-dimensional variable-range-hopping model. And superconductivity is still absent in the polycrystalline Sm$_{0.8}$Sr$_{0.2}$NiO$_2$.
|
[
"Physics Archive->cond-mat->cond-mat.supr-con"
] | 2020-10-22T14:55:15Z |
2101.01506
|
Structured Machine Learning Tools for Modelling Characteristics of Guided Waves
|
The use of ultrasonic guided waves to probe the materials/structures for damage continues to increase in popularity for non-destructive evaluation (NDE) and structural health monitoring (SHM). The use of high-frequency waves such as these offers an advantage over low-frequency methods from their ability to detect damage on a smaller scale. However, in order to assess damage in a structure, and implement any NDE or SHM tool, knowledge of the behaviour of a guided wave throughout the material/structure is important (especially when designing sensor placement for SHM systems). Determining this behaviour is extremely diffcult in complex materials, such as fibre-matrix composites, where unique phenomena such as continuous mode conversion takes place. This paper introduces a novel method for modelling the feature-space of guided waves in a composite material. This technique is based on a data-driven model, where prior physical knowledge can be used to create structured machine learning tools; where constraints are applied to provide said structure. The method shown makes use of Gaussian processes, a full Bayesian analysis tool, and in this paper it is shown how physical knowledge of the guided waves can be utilised in modelling using an ML tool. This paper shows that through careful consideration when applying machine learning techniques, more robust models can be generated which offer advantages such as extrapolation ability and physical interpretation.
|
[
"Computer Science Archive->cs.LG",
"Statistics Archive->stat.ML"
] | 2021-01-05T13:42:50Z |
2109.01560
|
Contextualized Embeddings based Convolutional Neural Networks for Duplicate Question Identification
|
Question Paraphrase Identification (QPI) is a critical task for large-scale Question-Answering forums. The purpose of QPI is to determine whether a given pair of questions are semantically identical or not. Previous approaches for this task have yielded promising results, but have often relied on complex recurrence mechanisms that are expensive and time-consuming in nature. In this paper, we propose a novel architecture combining a Bidirectional Transformer Encoder with Convolutional Neural Networks for the QPI task. We produce the predictions from the proposed architecture using two different inference setups: Siamese and Matched Aggregation. Experimental results demonstrate that our model achieves state-of-the-art performance on the Quora Question Pairs dataset. We empirically prove that the addition of convolution layers to the model architecture improves the results in both inference setups. We also investigate the impact of partial and complete fine-tuning and analyze the trade-off between computational power and accuracy in the process. Based on the obtained results, we conclude that the Matched-Aggregation setup consistently outperforms the Siamese setup. Our work provides insights into what architecture combinations and setups are likely to produce better results for the QPI task.
|
[
"Computer Science Archive->cs.CL"
] | 2021-09-03T14:30:09Z |
math-ph/0205029
|
p-Adic representation of the Cuntz algebra and the free coherent states
|
Representation of the Cuntz algebra in the space of (complex valued) functions on p-adic disk is introduced. The relation of this representation and the free coherent states is investigated.
|
[
"Mathematics Archive->math.MP",
"Physics Archive->math-ph"
] | 2002-05-21T12:17:05Z |
2202.12104
|
A Transformer-based Network for Deformable Medical Image Registration
|
Deformable medical image registration plays an important role in clinical diagnosis and treatment. Recently, the deep learning (DL) based image registration methods have been widely investigated and showed excellent performance in computational speed. However, these methods cannot provide enough registration accuracy because of insufficient ability in representing both the global and local features of the moving and fixed images. To address this issue, this paper has proposed the transformer based image registration method. This method uses the distinctive transformer to extract the global and local image features for generating the deformation fields, based on which the registered image is produced in an unsupervised way. Our method can improve the registration accuracy effectively by means of self-attention mechanism and bi-level information flow. Experimental results on such brain MR image datasets as LPBA40 and OASIS-1 demonstrate that compared with several traditional and DL based registration methods, our method provides higher registration accuracy in terms of dice values.
|
[
"Computer Science Archive->cs.CV",
"Computer Science Archive->cs.LG",
"Electrical Engineering and Systems Science Archive->eess.IV"
] | 2022-02-24T13:45:45Z |
2306.03491
|
SciCap+: A Knowledge Augmented Dataset to Study the Challenges of Scientific Figure Captioning
|
In scholarly documents, figures provide a straightforward way of communicating scientific findings to readers. Automating figure caption generation helps move model understandings of scientific documents beyond text and will help authors write informative captions that facilitate communicating scientific findings. Unlike previous studies, we reframe scientific figure captioning as a knowledge-augmented image captioning task that models need to utilize knowledge embedded across modalities for caption generation. To this end, we extended the large-scale SciCap dataset~\cite{hsu-etal-2021-scicap-generating} to SciCap+ which includes mention-paragraphs (paragraphs mentioning figures) and OCR tokens. Then, we conduct experiments with the M4C-Captioner (a multimodal transformer-based model with a pointer network) as a baseline for our study. Our results indicate that mention-paragraphs serves as additional context knowledge, which significantly boosts the automatic standard image caption evaluation scores compared to the figure-only baselines. Human evaluations further reveal the challenges of generating figure captions that are informative to readers. The code and SciCap+ dataset will be publicly available at https://github.com/ZhishenYang/scientific_figure_captioning_dataset
|
[
"Computer Science Archive->cs.CL",
"Computer Science Archive->cs.CV"
] | 2023-06-06T08:16:16Z |
2304.07096
|
Dynamic variable selection in high-dimensional predictive regressions
|
We develop methodology and theory for a general Bayesian approach towards dynamic variable selection in high-dimensional regression models with time-varying parameters. Specifically, we propose a variational inference scheme which features dynamic sparsity-inducing properties so that different subsets of ``active'' predictors can be identified over different time periods. We compare our modeling framework against established static and dynamic variable selection methods both in simulation and within the context of two common problems in macroeconomics and finance: inflation forecasting and equity returns predictability. The results show that our approach helps to tease out more accurately the dynamic impact of different predictors over time. This translates into significant gains in terms of out-of-sample point and density forecasting accuracy. We believe our results highlight the importance of taking a dynamic approach towards variable selection for economic modeling and forecasting.
|
[
"Statistics Archive->stat.ME"
] | 2023-04-14T12:36:02Z |
2207.06889
|
Nonreciprocal Amplification Transition in a Driven-Dissipative Quantum Network
|
We study the transport properties of a driven-dissipative quantum network, where multiple bosonic cavities such as photonic microcavities are coupled through a nonreciprocal bus with unidirectional transmission. For short-range coupling between the cavities, the occurrence of nonreciprocal amplification can be linked to a topological phase transition of the underlying dynamic Hamiltonian. However, for long-range coupling, we find that the nonreciprocal amplification transition deviates drastically from the topological phase transition. Nonetheless, we show that the nonreciprocal amplification transition can be connected to the emergence of zero-energy edge states of an auxiliary Hamiltonian with chiral symmetry even in the long-range coupling limit. We also investigate the stability, the crossover from short to long-range coupling, and the bandwidth of the nonreciprocal amplification. Our work has potential application in signal transmission and amplification, and also opens a window to non-Hermitian systems with long-range coupling and nontrivial boundary effects.
|
[
"Physics Archive->cond-mat->cond-mat.quant-gas",
"Physics Archive->physics->physics.atom-ph",
"Physics Archive->quant-ph"
] | 2022-07-14T13:07:27Z |
1907.04664
|
Orbital Angular Momentum (OAM) Mode Mixing in a Bent Step Index Fiber in Perturbation Theory
|
Within the framework of perturbation theory, we explore in detail the mixing of orbital angular momentum(OAM) modes due to a fiber bend in a step-index multimode fiber. Using scalar wave equation, we develop a complete set of analytic expressions for mode-mixing, including those for the $2\pi$ walk-off length, which is the distance traveled within the bent fiber before an OAM mode transforms into its negative topological charge counterpart, and back into itself. The derived results provide insight into the nature of the bend effects, clearly revealing the mathematical dependence on the bend radius and the topological charge. We numerically simulate the theoretical results with applications to a few-mode fiber and a multimode fiber, and calculate bend-induced modal crosstalk with implications for mode-multiplexed systems. The presented perturbation technique is general enough to be applicable to other perturbations like ellipticity and easily extendable to other fibers with step-index-like profile as in the ring fiber.
|
[
"Physics Archive->physics->physics.app-ph",
"Physics Archive->physics->physics.optics"
] | 2019-07-09T16:31:15Z |
1610.00394
|
Control Synthesis for Nonlinear Optimal Control via Convex Relaxations
|
This paper addresses the problem of control synthesis for nonlinear optimal control problems in the presence of state and input constraints. The presented approach relies upon transforming the given problem into an infinite-dimensional linear program over the space of measures. To generate approximations to this infinite-dimensional program, a sequence of Semi-Definite Programs (SDP)s is formulated in the instance of polynomial cost and dynamics with semi-algebraic state and bounded input constraints. A method to extract a polynomial control function from each SDP is also given. This paper proves that the controller synthesized from each of these SDPs generates a sequence of values that converge from below to the value of the optimal control of the original optimal control problem. In contrast to existing approaches, the presented method does not assume that the optimal control is continuous while still proving that the sequence of approximations is optimal. Moreover, the sequence of controllers that are synthesized using the presented approach are proven to converge to the true optimal control. The performance of the presented method is demonstrated on three examples.
|
[
"Mathematics Archive->math.OC"
] | 2016-10-03T02:55:11Z |
2211.12398
|
Generation of out-of-plane polarized spin current by spin swapping
|
The generation of spin currents and their application to the manipulation of magnetic states is fundamental to spintronics. Of particular interest are chiral antiferromagnets that exhibit properties typical of ferromagnetic materials even though they have negligible magnetization. Here, we report the generation of a robust spin current with both in-plane and out-of-plane spin polarization in epitaxial thin films of the chiral antiferromagnet Mn3Sn in proximity to permalloy thin layers. By employing temperature-dependent spin-torque ferromagnetic resonance, we find that the chiral antiferromagnetic structure of Mn3Sn is responsible for an in-plane polarized spin current that is generated from the interior of the Mn3Sn layer and whose temperature dependence follows that of this layer's antiferromagnetic order. On the other hand, the out-of-plane spin polarized spin current is unrelated to the chiral antiferromagnetic structure and is instead the result of scattering from the Mn3Sn/permalloy interface. We substantiate the later conclusion by performing studies with several other non-magnetic metals all of which are found to exhibit out-of-plane polarized spin currents arising from the spin swapping effect.
|
[
"Physics Archive->cond-mat->cond-mat.mes-hall",
"Physics Archive->cond-mat->cond-mat.mtrl-sci"
] | 2022-11-22T16:42:44Z |
math/0408319
|
Prime Number Races
|
This is a survey article on prime number races. Chebyshev noticed in the first half of the nineteenth century that for any given value of x, there always seem to be more primes of the form 4n+3 less than x then there are of the form 4n+1. Similar observations have been made with primes of the form 3n+2 and 3n+1, with primes of the form 10n+3/10n+7 and 10n+1/10n+9, and many others besides. More generally, one can consider primes of the form qn+a, qn+b, qn+c, >... for our favorite constants q, a, b, c, ... and try to figure out which forms are "preferred" over the others. In this paper, we describe these phenomena in greater detail and explain the efforts that have been made at understanding them.
|
[
"Mathematics Archive->math.NT"
] | 2004-08-24T00:03:21Z |
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