cometadata/datacite-rtg-text-other-reclassification-records huggingface dataset:
Conics meeting eight lines over perfect fields
Creators: name: Darwin, Cameron
name: Galimova, Aygul
name: Gu, Miao Pam
name: McKean, Stephen
Publisher: name: arXiv
Year: 2021
Subjects: subject: Algebraic Geometry (math.AG)
subject: FOS: Mathematics
subject: 14N15, 14F52

description: Over the complex numbers, there are 92 plane conics meeting 8 general lines in projective 3-space. Using the Euler class and local degree from motivic homotopy theory, we give an enriched version of this result over any perfect field. This provides a weighted count of the number of plane conics meeting 8 general lines, where the weight of each conic is determined the geometry of its intersections with the 8 given lines. As a corollary, real conics meeting 8 general lines come in two families of equal size.
description: 20 pages. Revised version with various errors corrected. Final version, but comments still welcome!
Anisotropic Babinet-invertible metasurfaces to realize transmission-reflection switching for orthogonal polarizations of light
Creators: name: Nakata, Yosuke
name: Urade, Yoshiro
name: Okimura, Kunio
name: Nakanishi, Toshihiro
name: Miyamaru, Fumiaki
name: Takeda, Mitsuo Wada
name: Kitano, Masao
Publisher: name: arXiv
Year: 2016
Subjects: subject: Optics (physics.optics)
subject: FOS: Physical sciences

description: The electromagnetic properties of an extremely thin metallic checkerboard drastically change from resonant reflection (transmission) to resonant transmission (reflection) when the local electrical conductivity at the interconnection points of the checkerboard is switched. To date, such critical transitions of metasurfaces have been applied only when they have 4-fold rotational symmetry, and their application to polarization control, which requires anisotropy, has been unexplored. To overcome this applicability limitation and open up new pathways for dynamic deep-subwavelength polarization control by utilizing critical transitions of checkerboard-like metasurfaces, we introduce a universal class of anisotropic Babinet-invertible metasurfaces enabling transmission-reflection switching for each orthogonally polarized wave. As an application of anisotropic Babinet-invertible metasurfaces, we experimentally realize a reconfigurable terahertz polarizer whose transmitting axis can be dynamically rotated by $90^\circ$.
description: 7 pages, 7 figures; the metadata is fixed
Three-dimensional imaging in nuclei
Creators: name: Alrashed, Mishary
name: Anderle, Daniele
name: Kang, Zhong-Bo
name: Terry, John
name: Xing, Hongxi
Publisher: name: arXiv
Year: 2021
Subjects: subject: High Energy Physics - Phenomenology (hep-ph)
subject: High Energy Physics - Experiment (hep-ex)
subject: Nuclear Experiment (nucl-ex)
subject: Nuclear Theory (nucl-th)
subject: FOS: Physical sciences

description: We perform the first simultaneous global QCD extraction of the transverse momentum dependent (TMD) parton distribution functions and the TMD fragmentation functions in nuclei. We have considered the world set of data from semi-inclusive electron-nucleus deep inelastic scattering and Drell-Yan di-lepton production. In total, this data set consists of 126 data points from HERMES, Fermilab, RHIC and LHC. Working at next-to-leading order and next-to-next-to-leading logarithmic accuracy, we achieve a $χ^2/dof = 1.045$. In this analysis, we quantify the broadening of TMDs in nuclei comparing with those in free nucleons for the first time. We also make predictions for the ongoing JLab 12 GeV program and future EIC measurements.
Dissipative Waves in Real Gases
Creators: name: Gupta, Neelam
name: Sharma, V. D.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Mathematical Physics (math-ph)
subject: FOS: Physical sciences

description: In this paper, we characterize a class of solutions to the unsteady 2-dimensional flow of a van der Waals fluid involving shock waves, and derive an asymptotic amplitude equation exhibiting quadratic and cubic nonlinearities including dissipation and diffraction. We exploit the theory of nonclassical symmetry reduction to obtain some exact solutions. Because of the nonlinearities present in the evolution equation, one expects that the wave profile will eventually encounter distortion and steepening which in the limit of vanishing dissipation culminates into a shock wave; and once shock is formed, it will propagate by separating the portions of the continuous region. Here we have shown how the real gas effects, which manifest themselves through the van der Waals parameters $\tilde{a}$ and $\tilde{b}$ influence the wave characteristics, namely the shape, strength, and decay behavior of shocks.
description: 10 pages
Galaxy formation in the Planck cosmology - IV. Mass and environmental quenching, conformity and clustering
Creators: name: Henriques, Bruno M. B.
name: White, Simon D. M.
name: Thomas, Peter A.
name: Angulo, Raul E.
name: Guo, Qi
name: Lemson, Gerard
name: Wang, Wenting
Publisher: name: arXiv
Year: 2016
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: FOS: Physical sciences

description: We study the quenching of star formation as a function of redshift, environment and stellar mass in the galaxy formation simulations of Henriques et al. (2015), which implement an updated version of the Munich semi-analytic model (L-GALAXIES) on the two Millennium Simulations after scaling to a Planck cosmology. In this model massive galaxies are quenched by AGN feedback depending on both black hole and hot gas mass, and hence indirectly on stellar mass. In addition, satellite galaxies of any mass can be quenched by ram-pressure or tidal stripping of gas and through the suppression of gaseous infall. This combination of processes produces quenching efficiencies which depend on stellar mass, host halo mass, environment density, distance to group centre and group central galaxy properties in ways which agree qualitatively with observation. Some discrepancies remain in dense regions and close to group centres, where quenching still seems too efficient. In addition, although the mean stellar age of massive galaxies agrees with observation, the assumed AGN feedback model allows too much ongoing star formation at late times. The fact that both AGN feedback and environmental effects are stronger in higher density environments leads to a correlation between the quenching of central and satellite galaxies which roughly reproduces observed conformity trends inside haloes.
description: Submitted to MNRAS; 21 pages, 16 figures
Weakly self-avoiding walk on a high-dimensional torus
Creators: name: Michta, Emmanuel
name: Slade, Gordon
Publisher: name: arXiv
Year: 2021
Subjects: subject: Probability (math.PR)
subject: Mathematical Physics (math-ph)
subject: FOS: Mathematics
subject: FOS: Physical sciences
subject: 60K35, 82B27, 82B41

description: How long does a self-avoiding walk on a discrete $d$-dimensional torus have to be before it begins to behave differently from a self-avoiding walk on $\mathbb{Z}^d$? We consider a version of this question for weakly self-avoiding walk on a torus in dimensions $d>4$. On $\mathbb{Z}^d$ for $d>4$, the partition function for $n$-step weakly self-avoiding walk is known to be asymptotically purely exponential, of the form $Aμ^n$, where $μ$ is the growth constant for weakly self-avoiding walk on $\mathbb{Z}^d$. We prove the identical asymptotic behaviour $Aμ^n$ on the torus (with the same $A$ and $μ$ as on $\mathbb{Z}^d$) until $n$ reaches order $V^{1/2}$, where $V$ is the number of vertices in the torus. This shows that the walk must have length of order at least $V^{1/2}$ before it "feels" the torus in its leading asymptotics. Our results support the conjecture that the behaviour of the partition function does change once $n$ reaches $V^{1/2}$, and we relate this to a conjectural critical scaling window which separates the dilute phase $n \ll V^{1/2}$ from the dense phase $n \gg V^{1/2}$. To prove the conjecture and to establish the existence of the scaling window remains a challenging open problem. The proof uses a novel lace expansion analysis based on the "plateau" for the torus two-point function obtained in previous work.
description: 43 pages, minor editorial improvements throughout the paper
Borel Summation and Analytic Continuation of the Heat Kernel on Hyperbolic Space
Creators: name: Dunne, Gerald V.
Publisher: name: arXiv
Year: 2021
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: Mathematical Physics (math-ph)
subject: FOS: Physical sciences

description: The heat kernel expansion on even-dimensional hyperbolic spaces is asymptotic at both short and long times, with interestingly different Borel properties for these short and long time expansions. Resummations in terms of incomplete gamma functions provide accurate extrapolations and analytic continuations, relating the heat kernel to the Schrodinger kernel, and the heat kernel on hyperbolic space to the heat kernel on spheres. For the diagonal heat kernel there is also a duality between short and long times which mixes the scalar and spinor heat kernels.
description: 14 pp, 13 figs; for Festschrift in honor of Peter Suranyi
Confidence and efficiency scaling in Variational Quantum Monte Carlo calculations
Creators: name: Delyon, François
name: Bernu, Bernard
name: Holzmann, Markus
Publisher: name: arXiv
Year: 2016
Subjects: subject: Computational Physics (physics.comp-ph)
subject: Data Analysis, Statistics and Probability (physics.data-an)
subject: FOS: Physical sciences

description: Based on the central limit theorem, we discuss the problem of evaluation of the statistical error of Monte Carlo calculations using a time discretized diffusion process. We present a robust and practical method to determine the effective variance of general observables and show how to verify the equilibrium hypothesis by the Kolmogorov-Smirnov test. We then derive scaling laws of the efficiency illustrated by Variational Monte Carlo calculations on the two dimensional electron gas.
description: 10 pages
Combinatorial properties of non-archimedean convex sets
Creators: name: Chernikov, Artem
name: Mennen, Alex
Publisher: name: arXiv
Year: 2021
Subjects: subject: Combinatorics (math.CO)
subject: Commutative Algebra (math.AC)
subject: Logic (math.LO)
subject: FOS: Mathematics
subject: 52A35, 52A20, 52A01, 12J25

description: We study combinatorial properties of convex sets over arbitrary valued fields. We demonstrate analogs of some classical results for convex sets over the reals (e.g. the fractional Helly theorem and Bárány's theorem on points in many simplices), along with some additional properties not satisfied by convex sets over the reals, including finite breadth and VC-dimension. These results are deduced from a simple combinatorial description of modules over the valuation ring in a spherically complete valued field.
description: v.2: 27 pages; some minor corrections following referees' reports; added a brief discussion of the other notions of convexity in valued fields (Section 5.2) and connections to the study of abstract convexity spaces (Section 5.3); accepted to the Pacific Journal of Mathematics
The role of conformal symmetry in gravity and the standard model
Creators: name: Lucat, Stefano
name: Prokopec, Tomislav
Publisher: name: arXiv
Year: 2016
Subjects: subject: High Energy Physics - Theory (hep-th)
subject: Cosmology and Nongalactic Astrophysics (astro-ph.CO)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: FOS: Physical sciences

description: In this paper we consider conformal symmetry in the context of manifolds with general affine connection. We extend the conformal transformation law of the metric to a general metric compatible affine connection, and find that it is a symmetry of both the geodesic equation and the Riemann tensor. We derive the generalised Jacobi equation and Raychaudhuri equation and show that they are both conformally invariant. Using the geodesic deviation~(Jacobi) equation we analyse the behaviour of geodesics in different conformal frames. Since we find that our version of conformal symmetry is exact in classical pure Einstein's gravity, we ask whether one can extend it to the standard model. We find that it is possible to write conformal invariant lagrangians in any dimensions for vector, fermion and scalar fields, but that such lagrangians are only gauge invariant in four dimensions. Provided one introduces a dilaton field, gravity can be conformally coupled to matter.
description: 33 pages ; 4 figures
Bulk Superconductivity Induced by In-plane Chemical Pressure Effect in Eu0.5La0.5FBiS2-xSex
Creators: name: Jinno, Gen
name: Jha, Rajveer
name: Yamada, Akira
name: Higashinaka, Ryuji
name: Matsuda, Tatsuma D.
name: Aoki, Yuji
name: Nagao, Masanori
name: Miura, Osuke
name: Mizuguchi, Yoshikazu
Publisher: name: arXiv
Year: 2016
Subjects: subject: Superconductivity (cond-mat.supr-con)
subject: Materials Science (cond-mat.mtrl-sci)
subject: FOS: Physical sciences

description: We have investigated Se substitution effect to superconductivity of an optimally-doped BiS2-based superconductor Eu0.5La0.5FBiS2. Eu0.5La0.5FBiS2-xSex samples with x = 0-1 were synthesized. With increasing x, in-plane chemical pressure is enhanced. For x = 0.6, 0.8, and 1, superconducting transitions with a large shielding volume fraction are observed in magnetic susceptibility measurements, and the highest Tc is 3.8 K for x = 0.8. From low-temperature electrical resistivity measurements, a zero-resistivity state is observed for all the samples, and the highest Tc is observed for x = 0.8. With increasing Se concentration, characteristics of electrical resistivity changes from semiconducting-like to metallic, suggesting that the emergence of bulk superconductivity is linked with the enhanced metallicity. A superconductivity phase diagram of the Eu0.5La0.5FBiS2-xSex superconductor is established. Temperature dependences of electrical resistivity show an anomalous two-step transition under high magnetic fields. Hence, the resistivity data are analyzed with assuming in-plane anisotropy of upper critical field.
description: 23 pages, 16 figures (including 10 supplemental materials), 2 tables as supplemental materials
When entanglement harvesting is not really harvesting
Creators: name: Tjoa, Erickson
name: Martín-Martínez, Eduardo
Publisher: name: arXiv
Year: 2021
Subjects: subject: Quantum Physics (quant-ph)
subject: General Relativity and Quantum Cosmology (gr-qc)
subject: High Energy Physics - Theory (hep-th)
subject: FOS: Physical sciences

description: We revisit the entanglement harvesting protocol when two detectors are in causal contact. We study the role of field-mediated communication in generating entanglement between the two detectors interacting with a quantum field. We provide a quantitative estimator of the relative contribution of communication versus genuine entanglement harvesting. For massless scalar fields in flat spacetime, we show that when two detectors can communicate via the field, the detectors do not really harvest entanglement from the field, and instead they get entangled only via the field-mediated communication channel. In other words, in these scenarios the entanglement harvesting protocol is truly "harvesting entanglement" from the field only when the detectors are not able to communicate. In contrast, for massive scalar fields both communication and genuine harvesting contribute equally to the bipartite entanglement when the detectors are causally connected. These results emphasize the importance of taking into account the causal relationships between two parties involved in this relativistic quantum information protocol before we can declare that it is truly entanglement harvesting.
description: 13+6 pages, 8 figures; REVTeX4-2; v2: updated to match published version; v3: fixed typos
Comment on arXiv:0709.3700 "Orientation dependence of the optical spectra in graphene at high frequencies"
Creators: name: Nguyen, Viet Hung
name: Nguyen, Huy-Viet
Publisher: name: arXiv
Year: 2016
Subjects: subject: Mesoscale and Nanoscale Physics (cond-mat.mes-hall)
subject: FOS: Physical sciences

description: Zhang et al. reported in [Phys. Rev. B 77, 241402(R) (2008)] a theoretical study of the optical spectra of monolayer graphene employing the Kubo formula within a tight-binding model. Their calculations predicted that at high frequencies the optical conductivity of graphene becomes strongly anisotropic. In particular, at frequencies comparable to the energy separation of the upper and lower bands at the $Γ$-point, the optical conductivity is strongly suppressed if the field polarization is along the zigzag direction while it is significantly high for the armchair one. We find that, unfortunately, this result is just a consequence of the incorrect determination of the current operator in k-space. Here, we present the standard scheme to obtain this operator correctly. As a result, we show that the optical conductivity of monolayer graphene is indeed isotropic, which is consistent with the results of other (both theoretical and experimental) studies in the literature.
description: submitted
The magnetic field and dust filaments in the Polaris Flare
Creators: name: Panopoulou, G. V.
name: Psaradaki, I.
name: Tassis, K.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Astrophysics of Galaxies (astro-ph.GA)
subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: FOS: Physical sciences

description: In diffuse molecular clouds, possible precursors of star-forming clouds, the effect of the magnetic field is unclear. In this work we compare the orientations of filamentary structures in the Polaris Flare, as seen through dust emission by Herschel, to the plane-of-the-sky magnetic field orientation ($\rm B_{pos}$) as revealed by stellar optical polarimetry with RoboPol. Dust structures in this translucent cloud show a strong preference for alignment with $\rm B_{pos}$. 70 % of field orientations are consistent with those of the filaments (within 30$^\circ$). We explore the spatial variation of the relative orientations and find it to be uncorrelated with the dust emission intensity and correlated to the dispersion of polarization angles. Concentrating in the area around the highest column density filament, and in the region with the most uniform field, we infer the $\rm B_{pos}$ strength to be 24 $-$ 120 $μ$G. Assuming that the magnetic field can be decomposed into a turbulent and an ordered component, we find a turbulent-to-ordered ratio of 0.2 $-$ 0.8, implying that the magnetic field is dynamically important, at least in these two areas. We discuss implications on the 3D field properties, as well as on the distance estimate of the cloud.
description: 14 pages, 12 figures, accepted by MNRAS
How contact patterns destabilize and modulate epidemic outbreaks
Creators: name: Zierenberg, Johannes
name: Spitzner, F. Paul
name: Dehning, Jonas
name: Priesemann, Viola
name: Weigel, Martin
name: Wilczek, Michael
Publisher: name: arXiv
Year: 2021
Subjects: subject: Physics and Society (physics.soc-ph)
subject: Populations and Evolution (q-bio.PE)
subject: FOS: Physical sciences
subject: FOS: Biological sciences

description: The spread of a contagious disease clearly depends on when infected individuals come into contact with susceptible ones. Such effects, however, have remained largely unexplored in the study of epidemic outbreaks. In particular, it remains unclear how the timing of contacts interacts with the latent and infectious stages of the disease. Here, we use real-world physical proximity data to study this interaction and find that the temporal statistics of actual human contact patterns i) destabilize epidemic outbreaks and ii) modulate the basic reproduction number. We explain both observations by distinct aspects of the observed contact patterns. On the one hand, we find the destabilization of outbreaks to be caused by temporal clustering of contacts leading to over-dispersed offspring distributions and increased probabilities of otherwise rare events (zero- and super-spreading). Notably, our analysis enables us to disentangle previously elusive sources of over-dispersion in empirical offspring distributions. On the other hand, we find the modulation of R0 to be caused by a periodically varying contact rate. Both mechanisms are a direct consequence of the memory in contact behavior, and we showcase a generative process that reproduces these non-Markovian statistics. Our results point to the importance of including non-Markovian contact timings into studies of epidemic outbreaks.
description: 10 pages, 4 figures plus supplementary information
Identifying four $INTEGRAL$ sources in the Galactic Plane via VLT/optical and $XMM$-$Newton$/X-ray spectroscopy
Creators: name: Rahoui, Farid
name: Tomsick, John A.
name: Krivonos, Roman
Publisher: name: arXiv
Year: 2016
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: We report on FORS2 spectroscopy aiming at the identification of four Galactic Plane sources discovered by $INTEGRAL$, IGR J18088-2741, IGR J18381-0924, IGR J17164-3803, and IGR J19173+0747, complemented by $XMM$-$Newton$ spectroscopy for IGR J18381-0924. The presence of broad emission lines of neutral H and He and a flat Balmer decrement Hα/Hβ show that IGR J18088-2741 is a cataclysmic variable located beyond 8 kpc. For IGR J18381-0924, the detection of red-shifted Hα and neutral O emission signatures and the absence of narrow forbidden emission lines point towards a low-luminosity Seyfert 1.9 nature at $z=0.031\pm0.002$. Its $XMM$-$Newton$ spectrum, best-fit by an absorbed $Γ=1.19\pm0.07$ power law combined with a $z=0.026_{-0.016}^{+0.008}$ red-shifted iron emission feature, is in agreement with this classification. The likely IGR J17164-3803 optical counterpart is an M2 III star at 3 to 4 kpc which, based on the X-ray spectrum of the source, is the companion of a white dwarf in an X-ray faint symbiotic system. Finally, we challenge the accepted identification of IGR J19173+0747 as an high mass X-ray binary. Indeed, the USNO optical counterpart is actually a blend of two objects located at the most likely 3 kpc distance, both lying within the error circle of the Swift position. The first is a cataclysmic variable, which we argue is the real nature of IGR J19173+0747. However, we cannot rule out the second one that we identify as an F3 V star that, if associated to IGR J19173+0747, likely belongs to a quiescent X-ray binary.
description: 10 pages, 8 figures, 4 tables. Accepted for publication in MNRAS
The Cauchy Problem for properly hyperbolic equations in one space variable
Creators: name: Taglialatela, Sergio Spagnolo Giovanni
Publisher: name: arXiv
Year: 2021
Subjects: subject: Analysis of PDEs (math.AP)
subject: FOS: Mathematics
subject: 35L30

description: In this paper we consider the Cauchy problem for higher order weakly hyperbolic equations. We assume that the principal symbol depends only on one space variable and the characteristic roots $τ_j$ verify the inequality \[τ_j^2(x) + τ_k^2(x) \le M \bigl(τ_j(x)-τ_k(x)\bigr)^2\] for some constant $M$ independent of $x$. We prove that if the lower order terms verify a suitable Levi condition, the Cauchy problem is well-posed in $\mathcal{C}$-infinity.
Local M-estimation with Discontinuous Criterion for Dependent and Limited Observations
Creators: name: Seo, Myung Hwan
name: Otsu, Taisuke
Publisher: name: arXiv
Year: 2016
Subjects: subject: Statistics Theory (math.ST)
subject: Methodology (stat.ME)
subject: FOS: Mathematics
subject: FOS: Computer and information sciences
subject: Primary 62F12, Secondary 60F17, 60G15, 62G20

description: This paper examines asymptotic properties of local M-estimators under three sets of high-level conditions. These conditions are sufficiently general to cover the minimum volume predictive region, conditional maximum score estimator for a panel data discrete choice model, and many other widely used estimators in statistics and econometrics. Specifically, they allow for discontinuous criterion functions of weakly dependent observations, which may be localized by kernel smoothing and contain nuisance parameters whose dimension may grow to infinity. Furthermore, the localization can occur around parameter values rather than around a fixed point and the observation may take limited values, which leads to set estimators. Our theory produces three different nonparametric cube root rates and enables valid inference for the local M-estimators, building on novel maximal inequalities for weakly dependent data. Our results include the standard cube root asymptotics as a special case. To illustrate the usefulness of our results, we verify our conditions for various examples such as the Hough transform estimator with diminishing bandwidth, maximum score-type set estimator, and many others.
The Galois module structure of holomorphic poly-differentials and Riemann-Roch spaces
Creators: name: Bleher, Frauke M.
name: Wood, Adam
Publisher: name: arXiv
Year: 2021
Subjects: subject: Algebraic Geometry (math.AG)
subject: Number Theory (math.NT)
subject: FOS: Mathematics
subject: Primary 11G20, Secondary 14H05, 14G17, 20C20

description: Suppose $X$ is a smooth projective geometrically irreducible curve over a perfect field $k$ of positive characteristic $p$. Let $G$ be a finite group acting faithfully on $X$ over $k$ such that $G$ has non-trivial, cyclic Sylow $p$-subgroups. If $E$ is a $G$-invariant Weil divisor on $X$ with $\mathrm{deg}(E)> 2g(X)-2$, we prove that the decomposition of $\mathrm{H}^0(X,\mathcal{O}_X(E))$ into a direct sum of indecomposable $kG$-modules is uniquely determined by the class of $E$ modulo $G$-invariant principal divisors, together with the ramification data of the cover $X\to X/G$. The latter is given by the lower ramification groups and the fundamental characters of the closed points of $X$ that are ramified in the cover. As a consequence, we obtain that if $m>1$ and $g(X)\ge 2$, then the $kG$-module structure of $\mathrm{H}^0(X,Ω_X^{\otimes m})$ is uniquely determined by the class of a canonical divisor on $X/G$ modulo principal divisors, together with the ramification data of $X\to X/G$. This extends to arbitrary $m > 1$ the $m = 1$ case treated by the first author with T. Chinburg and A. Kontogeorgis. We discuss applications to the tangent space of the global deformation functor associated to $(X,G)$ and to congruences between prime level cusp forms in characteristic $0$. In particular, we complete the description of the precise $k\mathrm{PSL}(2,\mathbb{F}_\ell)$-module structure of all prime level $\ell$ cusp forms of even weight in characteristic $p=3$.
description: 35 pages. The third version has been rewritten completely. The third version gives a more explicit algorithm and adds more explanations. It also continues to highlight the differences from arXiv:1707.07133
Spatial machine-learning model diagnostics: a model-agnostic distance-based approach
Creators: name: Brenning, Alexander
Publisher: name: arXiv
Year: 2021
Subjects: subject: Machine Learning (cs.LG)
subject: FOS: Computer and information sciences

description: While significant progress has been made towards explaining black-box machine-learning (ML) models, there is still a distinct lack of diagnostic tools that elucidate the spatial behaviour of ML models in terms of predictive skill and variable importance. This contribution proposes spatial prediction error profiles (SPEPs) and spatial variable importance profiles (SVIPs) as novel model-agnostic assessment and interpretation tools for spatial prediction models with a focus on prediction distance. Their suitability is demonstrated in two case studies representing a regionalization task in an environmental-science context, and a classification task from remotely-sensed land cover classification. In these case studies, the SPEPs and SVIPs of geostatistical methods, linear models, random forest, and hybrid algorithms show striking differences but also relevant similarities. Limitations of related cross-validation techniques are outlined, and the case is made that modelers should focus their model assessment and interpretation on the intended spatial prediction horizon. The range of autocorrelation, in contrast, is not a suitable criterion for defining spatial cross-validation test sets. The novel diagnostic tools enrich the toolkit of spatial data science, and may improve ML model interpretation, selection, and design.
Fast Yet Effective Machine Unlearning
Creators: name: Tarun, Ayush K
name: Chundawat, Vikram S
name: Mandal, Murari
name: Kankanhalli, Mohan
Publisher: name: arXiv
Year: 2021
Subjects: subject: Machine Learning (cs.LG)
subject: FOS: Computer and information sciences

description: Unlearning the data observed during the training of a machine learning (ML) model is an important task that can play a pivotal role in fortifying the privacy and security of ML-based applications. This paper raises the following questions: (i) can we unlearn a single or multiple class(es) of data from a ML model without looking at the full training data even once? (ii) can we make the process of unlearning fast and scalable to large datasets, and generalize it to different deep networks? We introduce a novel machine unlearning framework with error-maximizing noise generation and impair-repair based weight manipulation that offers an efficient solution to the above questions. An error-maximizing noise matrix is learned for the class to be unlearned using the original model. The noise matrix is used to manipulate the model weights to unlearn the targeted class of data. We introduce impair and repair steps for a controlled manipulation of the network weights. In the impair step, the noise matrix along with a very high learning rate is used to induce sharp unlearning in the model. Thereafter, the repair step is used to regain the overall performance. With very few update steps, we show excellent unlearning while substantially retaining the overall model accuracy. Unlearning multiple classes requires a similar number of update steps as for a single class, making our approach scalable to large problems. Our method is quite efficient in comparison to the existing methods, works for multi-class unlearning, does not put any constraints on the original optimization mechanism or network design, and works well in both small and large-scale vision tasks. This work is an important step towards fast and easy implementation of unlearning in deep networks. Source code: https://github.com/vikram2000b/Fast-Machine-Unlearning
description: Accepted in IEEE Transactions on Neural Networks and Learning Systems
Towards a Zero-Trust Micro-segmentation Network Security Strategy: An Evaluation Framework
Creators: name: Basta, Nardine
name: Ikram, Muhammad
name: Kaafar, Mohamed Ali
name: Walker, Andy
Publisher: name: arXiv
Year: 2021
Subjects: subject: Networking and Internet Architecture (cs.NI)
subject: FOS: Computer and information sciences

description: Micro-segmentation is an emerging security technique that separates physical networks into isolated logical micro-segments (workloads). By tying fine-grained security policies to individual workloads, it limits the attacker's ability to move laterally through the network, even after infiltrating the perimeter defences. While micro-segmentation is proved to be effective for shrinking enterprise networks attack surface, its impact assessment is almost absent in the literature. This research is dedicated to developing an analytical framework to characterise and quantify the effectiveness of micro-segmentation on enhancing networks security. We rely on a twofold graph-feature based framework of the network connectivity and attack graphs to evaluate the network exposure and robustness, respectively. While the former assesses the network assets connectedness, reachability and centrality, the latter depicts the ability of the network to resist goal-oriented attackers. Tracking the variations of formulated metrics values post the deployment of micro-segmentation reveals exposure reduction and robustness improvement in the range of 60% - 90%.
Controlling Wasserstein Distances by Kernel Norms with Application to Compressive Statistical Learning
Creators: name: Vayer, Titouan
name: Gribonval, Rémi
Publisher: name: arXiv
Year: 2021
Subjects: subject: Machine Learning (stat.ML)
subject: Machine Learning (cs.LG)
subject: FOS: Computer and information sciences

description: Comparing probability distributions is at the crux of many machine learning algorithms. Maximum Mean Discrepancies (MMD) and Wasserstein distances are two classes of distances between probability distributions that have attracted abundant attention in past years. This paper establishes some conditions under which the Wasserstein distance can be controlled by MMD norms. Our work is motivated by the compressive statistical learning (CSL) theory, a general framework for resource-efficient large scale learning in which the training data is summarized in a single vector (called sketch) that captures the information relevant to the considered learning task. Inspired by existing results in CSL, we introduce the Hölder Lower Restricted Isometric Property and show that this property comes with interesting guarantees for compressive statistical learning. Based on the relations between the MMD and the Wasserstein distances, we provide guarantees for compressive statistical learning by introducing and studying the concept of Wasserstein regularity of the learning task, that is when some task-specific metric between probability distributions can be bounded by a Wasserstein distance.
Octet and decuplet baryon $σ$-terms and mass decompositions
Creators: name: Copeland, P. M.
name: Ji, Chueng-Ryong
name: Melnitchouk, W.
Publisher: name: arXiv
Year: 2021
Subjects: subject: Nuclear Theory (nucl-th)
subject: High Energy Physics - Lattice (hep-lat)
subject: High Energy Physics - Phenomenology (hep-ph)
subject: FOS: Physical sciences

description: We present a comprehensive analysis of the SU(3) octet and decuplet baryon masses and $σ$-terms using high-precision lattice QCD data and chiral SU(3) effective theory with finite range regularization. The effects of various systematic uncertainties, including from the scale setting of the lattice data and the regularization prescriptions, are quantified. We find the pion-nucleon and strange nucleon $σ$-terms to be $σ_{πN} = 44(3)(3)$ MeV and $σ_{N s} = 50(6)(1)$ MeV, respectively. The results provide constraints on the energy-momentum tensor mass decompositions of the SU(3) octet and decuplet baryons, where we find the trace anomaly and quark/gluon energies decrease for strange baryons due to their larger strange $σ$-terms.
description: 12 pages, 6 figures
On the commuting probability of p-elements in a finite group
Creators: name: Burness, Timothy C.
name: Guralnick, Robert M.
name: Moretó, Alexander
name: Navarro, Gabriel
Publisher: name: arXiv
Year: 2021
Subjects: subject: Group Theory (math.GR)
subject: FOS: Mathematics

description: Let $G$ be a finite group, let $p$ be a prime and let ${\rm Pr}_p(G)$ be the probability that two random $p$-elements of $G$ commute. In this paper we prove that ${\rm Pr}_p(G) > (p^2+p-1)/p^3$ if and only if $G$ has a normal and abelian Sylow $p$-subgroup, which generalizes previous results on the widely studied commuting probability of a finite group. This bound is best possible in the sense that for each prime $p$ there are groups with ${\rm Pr}_p(G) = (p^2+p-1)/p^3$ and we classify all such groups. Our proof is based on bounding the proportion of $p$-elements in $G$ that commute with a fixed $p$-element in $G \setminus \textbf{O}_p(G)$, which in turn relies on recent work of the first two authors on fixed point ratios for finite primitive permutation groups.
description: Revised according to referee's report. To appear in Algebra & Number Theory
Causal Inference Despite Limited Global Confounding via Mixture Models
Creators: name: Gordon, Spencer L.
name: Mazaheri, Bijan
name: Rabani, Yuval
name: Schulman, Leonard J.
Publisher: name: arXiv
Year: 2021
Subjects: subject: Machine Learning (cs.LG)
subject: Data Structures and Algorithms (cs.DS)
subject: Signal Processing (eess.SP)
subject: Machine Learning (stat.ML)
subject: FOS: Computer and information sciences
subject: FOS: Electrical engineering, electronic engineering, information engineering
subject: F.2; G.3
subject: 68W40, 62F99, 62-09

description: A Bayesian Network is a directed acyclic graph (DAG) on a set of $n$ random variables (the vertices); a Bayesian Network Distribution (BND) is a probability distribution on the random variables that is Markovian on the graph. A finite $k$-mixture of such models is graphically represented by a larger graph which has an additional ``hidden'' (or ``latent'') random variable $U$, ranging in $\{1,\ldots,k\}$, and a directed edge from $U$ to every other vertex. Models of this type are fundamental to causal inference, where $U$ models an unobserved confounding effect of multiple populations, obscuring the causal relationships in the observable DAG. By solving the mixture problem and recovering the joint probability distribution with $U$, traditionally unidentifiable causal relationships become identifiable. Using a reduction to the more well-studied ``product'' case on empty graphs, we give the first algorithm to learn mixtures of non-empty DAGs.
description: Published in CleaR 2023
Applications of Grassmannian flows to coagulation systems
Creators: name: Doikou, Anastasia
name: Malham, Simon J. A.
name: Stylianidis, Ioannis
name: Wiese, Anke
Publisher: name: arXiv
Year: 2022
Subjects: subject: Analysis of PDEs (math.AP)
subject: Mathematical Physics (math-ph)
subject: Exactly Solvable and Integrable Systems (nlin.SI)
subject: FOS: Mathematics
subject: FOS: Physical sciences

description: We demonstrate how many classes of Smoluchowski-type coagulation models can be realised as multiplicative Grassmannian flows and are therefore linearisable, and thus integrable in this sense. First, we prove that a general Smoluchowski-type equation with a constant frequency kernel, that encompasses a large class of such models, is realisable as a multiplicative Grassmannian flow. Second, we establish that several other related constant kernel models can also be realised as such. These include: the Gallay--Mielke coarsening model; the Derrida--Retaux depinning transition model and a general mutliple merger coagulation model. Third, we show how the additive and multiplicative frequency kernel cases can be realised as rank-one analytic Grassmannian flows.
description: 16 pages. This is now a shorter, more focused, version of the previous manuscript. Some new material has been added in the final main section. arXiv admin note: substantial text overlap with arXiv:1905.05035
Zero-Shot Machine Unlearning
Creators: name: Chundawat, Vikram S
name: Tarun, Ayush K
name: Mandal, Murari
name: Kankanhalli, Mohan
Publisher: name: arXiv
Year: 2022
Subjects: subject: Machine Learning (cs.LG)
subject: Artificial Intelligence (cs.AI)
subject: FOS: Computer and information sciences

description: Modern privacy regulations grant citizens the right to be forgotten by products, services and companies. In case of machine learning (ML) applications, this necessitates deletion of data not only from storage archives but also from ML models. Due to an increasing need for regulatory compliance required for ML applications, machine unlearning is becoming an emerging research problem. The right to be forgotten requests come in the form of removal of a certain set or class of data from the already trained ML model. Practical considerations preclude retraining of the model from scratch after discarding the deleted data. The few existing studies use either the whole training data, or a subset of training data, or some metadata stored during training to update the model weights for unlearning. However, in many cases, no data related to the training process or training samples may be accessible for the unlearning purpose. We therefore ask the question: is it possible to achieve unlearning with zero training samples? In this paper, we introduce the novel problem of zero-shot machine unlearning that caters for the extreme but practical scenario where zero original data samples are available for use. We then propose two novel solutions for zero-shot machine unlearning based on (a) error minimizing-maximizing noise and (b) gated knowledge transfer. These methods remove the information of the forget data from the model while maintaining the model efficacy on the retain data. The zero-shot approach offers good protection against the model inversion attacks and membership inference attacks. We introduce a new evaluation metric, Anamnesis Index (AIN) to effectively measure the quality of the unlearning method. The experiments show promising results for unlearning in deep learning models on benchmark vision data-sets. The source code is available here: https://github.com/ayu987/zero-shot-unlearning
description: Accepted in IEEE Transactions on Information Forensics and Security (TIFS)
Subgroup congruences for groups of prime power order
Creators: name: Aivazidis, Stefanos
name: Loukaki, Maria
Publisher: name: arXiv
Year: 2022
Subjects: subject: Group Theory (math.GR)
subject: FOS: Mathematics

description: Given a $p$-group $G$ and a subgroup-closed class $\mathfrak{X}$, we associate with each $\mathfrak{X}$-subgroup $H$ certain quantities which count $\mathfrak{X}$-subgroups containing $H$ subject to further properties. We show in Theorem I that each one of the said quantities is always $\equiv 1 \pmod p$ if and only if the same holds for the others. In Theorem II we supplement the above result by focusing on normal $\mathfrak{X}$-subgroups and in Theorem III we obtain a sharpened version of a celebrated theorem of Burnside relative to the class of abelian groups of bounded exponent. Various other corollaries are also presented.
description: To appear at J. Algebra
Evolution of intermediate-mass X-ray binaries driven by magnetic braking of Ap/Bp stars: I. ultracompact X-ray binaries
Creators: name: Chen, Wen-Cong
name: Podsiadlowski, Philipp
Publisher: name: arXiv
Year: 2016
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences

description: It is generally believed that Ultracompact X-ray binaries (UCXBs) evolved from binaries consisting of a neutron star accreting from a low-mass white dwarf or helium star where mass transfer is driven by gravitational radiation. However, the standard white-dwarf evolutionary channel cannot produce the relatively long-period ($40 - 60$\,min) UCXBs with high time-averaged mass-transfer rate. In this work, we explore an alternative evolutionary route toward UCXBs where the companions evolve from intermediate-mass Ap/Bp stars with an anomalously strong magnetic field ($100 - 10000$\,G). Including the magnetic braking caused by the coupling between the magnetic field and an irradiation-driven wind induced by the X-ray flux from the accreting component, we show that intermediate-mass X-ray binaries (IMXBs) can evolve into UCXBs. Using the \emph{MESA} code, we have calculated evolutionary sequences for a large number of IMXBs. The simulated results indicate that, for a small wind-driving efficiency $f=10^{-5}$, the anomalous magnetic braking can drive IMXBs to an ultra-short period of 11 min. Comparing our simulated results with the observed parameters of fifteen identified UCXBs, the anomalous magnetic braking evolutionary channel can account for the formation of seven and eight sources with $f=10^{-3}$, and $10^{-5}$, respectively. In particular, a relatively large value of $f$ can fit three of the long-period, persistent sources with high mass-transfer rate. Though the proportion of Ap/Bp stars in intermediate-mass stars is only 5\%, the lifetime of the UCXB phase is $\gtrsim$ 2 Gyr, producing a relatively high number of observable systems, making this an alternative evolutionary channel for the formation of UCXBs.
description: 10 pages, 9 figures, 2 tables, accepted for publication in ApJ
Experimentally freezing quantum discord in a dissipative environment using dynamical decoupling
Creators: name: Singh, Harpreet
name: Arvind
name: Dorai, Kavita
Publisher: name: arXiv
Year: 2016
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: The discovery of the intriguing phenomenon that certain kinds of quantum correlations remain impervious to noise up to a specific point in time and then suddenly decay, has generated immense recent interest. We exploit dynamical decoupling sequences to prolong the persistence of time-invariant quantum discord in a system of two NMR qubits decohering in independent dephasing environments. We experimentally prepare two-qubit Bell-diagonal quantum states that interact with individual dephasing channels and demonstrate the effect of dynamical decoupling on the preservation of both quantum and classical correlations. We are able to freeze quantum discord over long time scales in the presence of noise, using dynamical decoupling. We use robust state-independent dynamical decoupling schemes for state preservation and demonstrate that these schemes are able to successfully preserve quantum discord.
description: Revtex4.1 7 eps figures
TRacer: Scalable Graph-based Transaction Tracing for Account-based Blockchain Trading Systems
Creators: name: Wu, Zhiying
name: Liu, Jieli
name: Wu, Jiajing
name: Zheng, Zibin
Publisher: name: arXiv
Year: 2022
Subjects: subject: Cryptography and Security (cs.CR)
subject: FOS: Computer and information sciences

description: Security incidents such as scams and hacks, have become a major threat to the health of the blockchain ecosystem, causing billions of dollars in losses each year for blockchain users. To reveal the real-world entities behind the pseudonymous blockchain account and recover the stolen funds from the massive transaction data, much effort has been devoted to tracing the flow of illicit funds in blockchains recently. However, most current tracing approaches based on heuristics and taint analysis have limitations in terms of universality, effectiveness, and efficiency. This paper models the blockchain transaction records as a blockchain transaction graph and tackles blockchain transaction tracing as a graph searching task. We propose TRacer, a scalable transaction tracing tool for account-based blockchains. To infer the relevance between accounts during graph searching, we develop a novel personalized PageRank method in TRacer based on the directed, weighted, temporal, and multi-relationship blockchain transaction graphs. To the best of our knowledge, TRacer is the first intelligent transaction tracing tool in account-based blockchains that can handle complex transaction actions in decentralized finance (DeFi). Experimental results and theoretical analysis prove that TRacer can complete the transaction tracing task effectively at a low cost. All codes of TRacer are available at GitHub.
Active demultiplexing of single-photons from a solid-state source
Creators: name: Lenzini, F.
name: Haylock, B.
name: Loredo, J. C.
name: Abrahao, R. A.
name: Zakaria, N. A.
name: Kasture, S.
name: Sagnes, I.
name: Lemaitre, A.
name: Phan, H. -P.
name: Dao, D. V.
name: Senellart, P.
name: Almeida, M. P.
name: White, A. G.
name: Lobino, M.
Publisher: name: arXiv
Year: 2016
Subjects: subject: Quantum Physics (quant-ph)
subject: FOS: Physical sciences

description: A scheme for active temporal-to-spatial demultiplexing of single-photons generated by a solid-state source is introduced. The scheme scales quasi-polynomially with photon number, providing a viable technological path for routing n photons in the one temporal stream from a single emitter to n different spatial modes. The active demultiplexing is demonstrated using a state-of-the-art photon source---a quantum-dot deterministically coupled to a micropillar cavity---and a custom-built demultiplexer---a network of electro-optically reconfigurable waveguides monolithically integrated in a lithium niobate chip. The measured demultiplexer performance can enable a six-photon rate three orders of magnitude higher than the equivalent heralded SPDC source, providing a platform for intermediate quantum computation protocols.
description: 4 pages, 2 figures