cssi/SciSciGPT-SciSciNet huggingface dataset:
Evidence from the Very Long Baseline Array that J1502SE/SW are Double Hotspots, not a Supermassive Binary Black Hole

SDSS J150243.09+111557.3 is a merging system at z = 0.39 that hosts two confirmed active galactic nuclei (AGNs), one unobscured and one dust-obscured, offset by several kiloparsecs. Deane et al. recently reported evidence from the European VLBI Network (EVN) that the dust-obscured AGN exhibits two flat-spectrum radio sources, J1502SE/SW, offset by 26 mas (140 pc), with each source being energized by its own supermassive black hole (BH). This intriguing interpretation of a close binary BH was reached after ruling out a double-hotspot scenario, wherein both hotspots are energized by a single, central BH, a configuration occurring in the well-studied compact symmetric objects. When observed with sufficient sensitivity and resolution, an object with double hotspots should have an edge-brightened structure. We report evidence from the Very Long Baseline Array (VLBA) for just such a structure in an image of the obscured AGN with higher sensitivity and resolution than the EVN images. We thus conclude that a double-hotspot scenario should be reconsidered as a viable interpretation for J1502SE/SW, and suggest further VLBA tests of that scenario. A double-hotspot scenario could have broad implications for feedback in obscured AGNs. We also report a VLBA detection of high-brightness-temperature emission from the unobscured AGN that is offset several kiloparsecs from J1502SE/SW.
Orientifolds and the refined topological string

We study refined topological string theory in the presence of orientifolds by counting second-quantized BPS states in M-theory. This leads us to propose a new integrality condition for both refined and unrefined topological strings when orientifolds are present. We define the SO(2N) refined Chern-Simons theory which computes refined open string amplitudes for branes wrapping Seifert three-manifolds. We use the SO(2N) refined Chern-Simons theory to compute new invariants of torus knots that generalize the Kauffman polynomials. At large N, the SO(2N) refined Chern-Simons theory on S 3 is dual to refined topological strings on an orientifold of the resolved conifold, generalizing the Gopakumar-Sinha-Vafa duality. Finally, we use the (2, 0) theory to define and solve refined Chern-Simons theory for all ADE gauge groups.
Kinetic study of radiation-reaction-limited particle acceleration during the relaxation of unstable force-free equilibria

Many powerful and variable gamma-ray sources, including pulsar wind nebulae, active galactic nuclei and gamma-ray bursts, seem capable of accelerating particles to gamma-ray emitting energies efficiently over very short timescales. These are likely due to the rapid dissipation of electromagnetic energy in a highly magnetized, relativistic plasma. In order to understand the generic features of such processes, we have investigated simple models based on the relaxation of unstable force-free magnetostatic equilibria. In this work, we make the connection between the corresponding plasma dynamics and the expected radiation signal, using 2D particle-in-cell simulations that self-consistently include synchrotron radiation reactions. We focus on the lowest order unstable force-free equilibrium in a 2D periodic box. We find that rapid variability, with modest apparent radiation efficiency as perceived by a fixed observer, can be produced during the evolution of the instability. The "flares" are accompanied by an increased polarization degree in the high energy band, with rapid variation in the polarization angle. Furthermore, the separation between the acceleration sites and the synchrotron radiation sites for the highest energy particles facilitates acceleration beyond the synchrotron radiation reaction limit. We also discuss the dynamical consequences of the radiation reaction, and some astrophysical applications of this model.more » Our current simulations with numerically tractable parameters are not yet able to reproduce the most dramatic gamma-ray flares, e.g., from the Crab Nebula. As a result, higher magnetization studies are promising and will be carried out in the future.« less
Absolute Dimensions of the F-type Eclipsing Binary V2154 Cygni

We report spectroscopic observations of the 2.63 day, detached, F-type main-sequence eclipsing binary V2154 Cyg. We use our observations together with existing $uvby$ photometric measurements to derive accurate absolute masses and radii for the stars good to better than 1.5%. We obtain masses of M1 = 1.269 +/- 0.017 M(Sun) and M2 = 0.7542 +/- 0.0059 M(Sun), radii of R1 = 1.477 +/- 0.012 R(Sun) and R2 = 0.7232 +/- 0.0091 R(Sun), and effective temperatures of 6770 +/- 150 K and 5020 +/- 150 K for the primary and secondary stars, respectively. Both components appear to have their rotations synchronized with the motion in the circular orbit. A comparison of the properties of the primary with current stellar evolution models gives good agreement for a metallicity of [Fe/H] = -0.17, which is consistent with photometric estimates, and an age of about 2.2 Gyr. On the other hand, the K2 secondary is larger than predicted for its mass by about 4%. Similar discrepancies are known to exist for other cool stars, and are generally ascribed to stellar activity. The system is in fact an X-ray source, and we argue that the main site of the activity is the secondary star. Indirect estimates give a strength of about 1 kG for the surface magnetic field on that star. A previously known close visual companion to V2154 Cyg is shown to be physically bound, making the system a hierarchical triple.
(4, 2)-Choosability of Planar Graphs with Forbidden Structures

All planar graphs are 4-colorable and 5-choosable, while some planar graphs are not 4-choosable. Determining which properties guarantee that a planar graph can be colored using lists of size four has received significant attention. In terms of constraining the structure of the graph, for any $$\ell \in \{3,4,5,6,7\}$$ , a planar graph is 4-choosable if it is $$\ell $$ -cycle-free. In terms of constraining the list assignment, one refinement of k-choosability is choosability with separation. A graph is (k, s)-choosable if the graph is colorable from lists of size k where adjacent vertices have at most s common colors in their lists. Every planar graph is (4, 1)-choosable, but there exist planar graphs that are not (4, 3)-choosable. It is an open question whether planar graphs are always (4, 2)-choosable. A chorded $$\ell $$ -cycle is an $$\ell $$ -cycle with one additional edge. We demonstrate for each $$\ell \in \{5,6,7\}$$ that a planar graph is (4, 2)-choosable if it does not contain chorded $$\ell $$ -cycles.
Operational resilience: Concepts, design and analysis

Building resilience into today's complex infrastructures is critical to the daily functioning of society and its ability to withstand and recover from natural disasters, epidemics, and cyber-threats. This study proposes quantitative measures that capture and implement the definition of engineering resilience advanced by the National Academy of Sciences. The approach is applicable across physical, information, and social domains. It evaluates the critical functionality, defined as a performance function of time set by the stakeholders. Critical functionality is a source of valuable information, such as the integrated system resilience over a time interval, and its robustness. The paper demonstrates the formulation on two classes of models: 1) multi-level directed acyclic graphs, and 2) interdependent coupled networks. For both models synthetic case studies are used to explore trends. For the first class, the approach is also applied to the Linux operating system. Results indicate that desired resilience and robustness levels are achievable by trading off different design parameters, such as redundancy, node recovery time, and backup supply available. The nonlinear relationship between network parameters and resilience levels confirms the utility of the proposed approach, which is of benefit to analysts and designers of complex systems and networks.
Putting positrons into classical Dirac field theory

Abstract One way of arriving at a quantum field theory of electrons and positrons is to take a classical theory of the Dirac field and then quantize. Starting with the standard classical field theory and quantizing in the most straightforward way yields an inadequate quantum field theory. It is possible to fix this theory by making some modifications (such as redefining the operators for energy and charge). Here I argue that we ought to make these modifications earlier, revising the classical Dirac field theory that serves as the starting point for quantization (putting positrons into that theory and removing negative energies). Then, quantization becomes straightforward. Also, the physics of the Dirac field is made more similar to the physics of the electromagnetic field and we are able to better understand electron spin.
Morse Code Datasets for Machine Learning

We present an algorithm to generate synthetic datasets of tunable difficulty on classification of Morse code symbols for supervised machine learning problems, in particular, neural networks. The datasets are spatially one-dimensional and have a small number of input features, leading to high density of input information content. This makes them particularly challenging when implementing network complexity reduction methods. We explore how network performance is affected by deliberately adding various forms of noise and expanding the feature set and dataset size. Finally, we establish several metrics to indicate the difficulty of a dataset, and evaluate their merits. The algorithm and datasets are open-source.
Dynamic shrinkage processes

We propose a novel class of dynamic shrinkage processes for Bayesian time series and regression analysis. Building on a global–local framework of prior construction, in which continuous scale mixtures of Gaussian distributions are employed for both desirable shrinkage properties and computational tractability, we model dependence between the local scale parameters. The resulting processes inherit the desirable shrinkage behaviour of popular global–local priors, such as the horseshoe prior, but provide additional localized adaptivity, which is important for modelling time series data or regression functions with local features. We construct a computationally efficient Gibbs sampling algorithm based on a Polya–gamma scale mixture representation of the process proposed. Using dynamic shrinkage processes, we develop a Bayesian trend filtering model that produces more accurate estimates and tighter posterior credible intervals than do competing methods, and we apply the model for irregular curve fitting of minute‐by‐minute Twitter central processor unit usage data. In addition, we develop an adaptive time varying parameter regression model to assess the efficacy of the Fama–French five‐factor asset pricing model with momentum added as a sixth factor. Our dynamic analysis of manufacturing and healthcare industry data shows that, with the exception of the market risk, no other risk factors are significant except for brief periods.
Compact Quiescent Galaxies at Intermediate Redshifts

From several searches of the area common to the Sloan Digital Sky Survey and the United Kingdom Infrared Telescope Infrared Deep Sky Survey, we have selected 22 luminous galaxies between z ∼ 0.4 and z ∼ 0.9 that have colors and sizes similar to those of the compact quiescent galaxies at z > 2. By exploring structural parameters and stellar populations, we found that most of these galaxies actually formed most of their stars at z 2. Several of these young objects are disk-like or possibly prolate. This lines up with several previous studies that found that massive quiescent galaxies at high redshifts often have disk-like morphologies. If these galaxies were to be confirmed to be disk-like, their formation mechanism must be able to account for both compactness and disks. On the other hand, if these galaxies were to be confirmed to be prolate, the fact that prolate galaxies do not exist in the local universe would indicate that galaxy formation mechanisms have evolved over cosmic time. We also found five galaxies forming over 80% of their stellar masses at z > 2. Three of these galaxiesmore » appear to have been modified to have spheroid-like morphologies, in agreement with the scenario of 'inside-out' buildup of massive galaxies. The remaining galaxies, SDSS J014355.21+133451.4 and SDSS J115836.93+021535.1, have truly old stellar populations and disk-like morphologies. These two objects would be good candidates for nearly unmodified compact quiescent galaxies from high redshifts that are worth future study.« less
Reflected Light Phase Curves in the TESS Era

The reflected light signal from a planet throughout its orbit is a powerful probe of a planet's atmospheric properties. There are a number of planets that are amenable to reflected light phase curve studies with present and future space-based instrumentation and here we assess our ability to characterize these worlds. Using simulated TESS populations we identify the Nine, a set of archetypal exoplanets with the potential to be bright in reflected light, because of their radii and proximity to their star, while still being cool enough to have minimal thermal contamination at optical wavelengths. For each planet we compute albedo spectra for several cloud and atmosphere assumptions (e.g. thermochemical equilibrium, solar composition). We find that in the TESS bandpass the estimated contrast at optical wavelengths is typically <10 ppm except for the brightest, largest, or closest in planets with the highest lofted clouds where contrast can reach a few tens of ppm. Meanwhile, in a bluer bandpass (0.3--0.5 microns) the estimated contrast can be as high as 150 ppm but typically 10-50 ppm. In the temperature range of interest, planets with the highest, most extensive cloud decks are generally darker at bluer wavelengths than cloudless planets because of the low single scattering albedos of their primary condensate constituents. Our models suggest that Neptune-sized planets with relatively low insolation and small semi-major axes are the most conducive to reflected light phase curve studies in TESS.
Realization and Properties of Biochemical-Computing Biocatalytic XOR Gate Based on Signal Change

We consider a realization of the XOR logic gate in a system involving two competing biocatalytic reactions, for which the logic-1 output is defined by these two processes causing a change in the optically detected signal. A model is developed for describing such systems in an approach suitable for evaluation of the analog noise amplification properties of the gate and optimization of its functioning. The initial data are fitted for gate quality evaluation within the developed model, and then modifications are proposed and experimentally realized for improving the gate functioning.
Generating levels that teach mechanics

The automatic generation of game tutorials is a challenging AI problem. While it is possible to generate annotations and instructions that explain to the player how the game is played, this paper focuses on generating a gameplay experience that introduces the player to a game mechanic. It evolves small levels for the Mario AI Framework that can only be beaten by an agent that knows how to perform specific actions in the game. It uses variations of a perfect A* agent that are limited in various ways, such as not being able to jump high or see enemies, to test how failing to do certain actions can stop the player from beating the level.
Leading slow roll corrections to the volume of the universe and the entropy bound

We make an extension to recent calculations of the probability density ρ(V ) for the volume of the universe after inflation. Previous results have been accurate to leading order in the slow roll parameters $$ \in \equiv \overset{\cdot }{H}/{H}^2 $$ and $$ \eta \equiv \overset{\cdot \cdot }{\phi }/\left(\overset{\cdot }{\phi }H\right) $$ , and 1/N c , where H is the Hubble parameter and N c is the classical number of e-foldings. Here, we present a modification which captures effects of order ϵN c , which amounts to letting the parameters of inflation H and $$ \overset{\cdot }{\phi } $$ depend on the value of the inflaton ϕ. The phase of slow roll eternal inflation can be defined as when the probability to have an infinite volume is greater than zero. Using this definition, we study the Laplace transform of ρ(V ) numerically to determine the condition that triggers the transition to eternal inflation. We also study the average volume 〈V 〉 analytically and show that it satisfies the universal volume bound. This bound states that, in any realization of inflation which ends with a finite volume, an initial volume must grow by less than a factor of $$ {e}^{S_{\mathrm{dS}}/2} $$ , where S dS is the de Sitter (dS) entropy.
Trust in AutoML: exploring information needs for establishing trust in automated machine learning systems

We explore trust in a relatively new area of data science: Automated Machine Learning (AutoML). In AutoML, AI methods are used to generate and optimize machine learning models by automatically engineering features, selecting models, and optimizing hyperparameters. In this paper, we seek to understand what kinds of information influence data scientists' trust in the models produced by AutoML? We operationalize trust as a willingness to deploy a model produced using automated methods. We report results from three studies - qualitative interviews, a controlled experiment, and a card-sorting task - to understand the information needs of data scientists for establishing trust in AutoML systems. We find that including transparency features in an AutoML tool increased user trust and understandability in the tool; and out of all proposed features, model performance metrics and visualizations are the most important information to data scientists when establishing their trust with an AutoML tool.
Vectorized Character Counting for Faster Pattern Matching

Many modern sequence alignment tools implement fast string matching using the space efficient data structure called a FM-index. The succinct nature of this data structure presents unique challenges for the algorithm designers. In this paper, we explore the opportunities for parallelization of the exact and inexact matches, and present an efficient solution for the Occ portion of the algorithm that utilizes the instruction-level parallelism of the modern CPUs. Our implementation computes all eight Occ values required for the inexact match algorithm step in a single pass. We showcase the algorithm performance in a multi-core genome aligner and discuss effects of the memory prefetch.
The Golden Era of Neutron Stars: From Hadrons to Quarks

Neutron stars were first posited in the early thirties, and discovered as pulsars in late sixties; however, only recently are we beginning to understand the matter they contain. This talk describes the continuing development of a consistent picture of the liquid interiors of neutron stars, driven by four advances: observations of two heavy neutron stars with masses $\simeq$ 2.0 solar masses; inferences of masses and radii simultaneously for an increasing number of neutron stars in low mass X-ray binaries, and future determinations via the NICER observatory; the observation of the binary neutron star merger, GW170817, through gravitational waves as well as across the electromagnetic spectrum; and an emerging understanding in QCD of how nuclear matter can turn into deconfined quark matter in the interior. We describe the modern quark-hadron crossover equation of state, QHC18, and the corresponding neutron stars, which agree well with current observations.
Group actions on Segal operads

We give a Quillen equivalence between model structures for simplicial operads, described via the theory of operads, and Segal operads, thought of as certain reduced dendroidal spaces. We then extend this result to give a Quillen equivalence between the model structures for simplicial operads equipped with a group action and the corresponding Segal operads.
Fourier Series of Circle Embeddings

We study the Fourier series of circle homeomorphisms and circle embeddings, with an emphasis on the Blaschke product approximation and the vanishing of Fourier coefficients. The analytic properties of the Fourier series are related to the geometry of the circle embeddings, and have implications for the curvature of minimal surfaces.
Mollified Monte Carlo

Abstract Using a common technique [ 1, 2] for approximating distributions [generalized functions], we are able to use standard Monte Carlo methods to compute QFT quantities in Minkowski spacetime, under phase transitions, or when dealing with coalescing stationary points.
SUPERGRANULES AS PROBES OF SOLAR CONVECTION ZONE DYNAMICS

Supergranules are convection cells seen at the Sun’s surface as a space filling pattern of horizontal flows. While typical supergranules have diameters of about 35 Mm, they exhibit a broad spectrum of sizes from ∼10 Mm to ∼100 Mm. Here we show that supergranules of different sizes can be used to probe the rotation rate in the Sun’s outer convection zone. We find that the equatorial rotation rate as a function of depth as measured by global helioseismology matches the equatorial rotation as a function of wavelength for the supergranules. This suggests that supergranules are advected by flows at depths equal to their wavelengths and thus can be used to probe flows at those depths. The supergranule rotation profiles show that the surface shear layer, through which the rotation rate increases inward, extends to depths of ∼50 Mm and to latitudes of at least 70 ◦ . Typical supergranules are well observed at high latitudes and have a range of sizes that extend to greater depths than those typically available for measuring subsurface flows with local helioseismology. These characteristics indicate that probing the solar convection zone dynamics with supergranules can complement the results of helioseismology.
Purely Singular Continuous Spectrum for CMV Operators Generated by Subshifts

We prove uniform absence of point spectrum for CMV operators corresponding to the period doubling subshift. We also prove almost sure absence of point spectrum for CMV operators corresponding to a class of Sturmian subshifts. Lastly, we prove almost sure absence of point spectrum for CMV operators corresponding to some subshifts generated by a coding of a rotation.
Temperature effects in the thermal conductivity of aligned amorphous polyethylene—A molecular dynamics study

We analyze, through molecular dynamics simulations, the temperature dependence of the thermal conductivity (k) of chain-oriented amorphous polyethylene (PE). We find that at increasing levels of orientation, the temperature corresponding to a peak k progressively decreases. Un-oriented PE exhibits the peak k at 350 K, while aligned PE under an applied strain of 400% shows a maximum at 100 K. This transition of peak k to lower temperatures with increasing alignment is explained in terms of a crossover from disorder to anharmonicity dominated phonon transport in aligned polymers. Evidence for this crossover is achieved by manipulating the disorder in the polymer structure and studying the resulting change in temperature corresponding to peak k. Disorder is modified through a change in the dihedral parameters of the potential function, allowing a change in the relative fraction of trans and gauche transformations. The results shed light on the underlying thermal transport processes in aligned polymers and hold importance for low temperature applications of polymer materials in thermal management technologies.
Photonic Molecules and Spectral Engineering

This chapter reviews the fundamental optical properties and applications of photonic molecules (PMs) – photonic structures formed by electromagnetic coupling of two or more optical microcavities (photonic atoms). Controllable interaction between light and matter in photonic atoms can be further modified and enhanced by the manipulation of their mutual coupling. Mechanical and optical tunability of PMs not only adds new functionalities to microcavity-based optical components but also paves the way for their use as testbeds for the exploration of novel physical regimes in atomic physics and quantum optics. Theoretical studies carried on for over a decade yielded novel PM designs that make possible lowering thresholds of semiconductor microlasers, producing directional light emission, achieving optically induced transparency, and enhancing sensitivity of microcavity-based bio-, stress-, and rotation sensors. Recent advances in material science and nano-fabrication techniques make possible the realization of optimally tuned PMs for cavity quantum electrodynamic experiments, classical and quantum information processing, and sensing.
$R$-parity Violating Decays of Bino Neutralino LSPs at the LHC

The R-parity violating decays of Bino neutralino LSPs are analyzed within the context of the B − L MSSM “heterotic standard model”. These LSPs correspond to statistically determined initial soft supersymmetry breaking parameters which, when evolved using the renormalization group equations, lead to an effective theory satisfying all phenomenological requirements; including the observed electroweak vector boson masses and the Higgs mass. The explicit RPV decay channels of these LSPs into standard model particles, the analytic and numerical decay rates and the associated branching ratios are presented. The analysis of these quantities breaks into two separate calculations; first, for Bino neutralino LSPs with mass larger than MW± and, second, when the Bino neutralino mass is smaller than the electroweak scale. The RPV decay processes in both of these regions is analyzed in detail. The decay lengths of these RPV interactions are discussed. It is shown that for heavy Bino neutralino LSPs the vast majority of these decays are “prompt”, although a small, but calculable, number correspond to “displaced” decays of various lengths. The situation is reversed for light Bino LSPs, only a small number of which can RPV decay promptly. The relation of these results to the neutrino hierarchy — either normal or inverted — is discussed in detail.
Modeling the Anomalous Microwave Emission with Spinning Nanoparticles: No PAHs Required

In light of recent observational results indicating an apparent lack of correlation between the Anomalous Microwave Emission (AME) and mid-infrared emission from polycyclic aromatic hydrocarbons (PAHs), we assess whether rotational emission from spinning silicate and/or iron nanoparticles could account for the observed AME without violating observational constraints on interstellar abundances, ultraviolet extinction, and infrared emission. By modifying the SpDust code to compute the rotational emission from these grains, we find that nanosilicate grains could account for the entirety of the observed AME, whereas iron grains could be responsible for only a fraction, even for extreme assumptions on the amount of interstellar iron concentrated in ultrasmall iron nanoparticles. Given the added complexity of contributions from multiple grain populations to the total spinning dust emission, as well as existing uncertainties due to the poorly-constrained grain size, charge, and dipole moment distributions, we discuss generic, carrier-independent predictions of spinning dust theory and observational tests that could help identify the AME carrier(s).
APODIZED PUPIL LYOT CORONAGRAPHS FOR ARBITRARY APERTURES. IV. REDUCED INNER WORKING ANGLE AND INCREASED ROBUSTNESS TO LOW-ORDER ABERRATIONS

The Apodized Pupil Lyot Coronagraph (APLC) is a diffraction suppression system installed in the recently deployed instruments Palomar/P1640, Gemini/GPI, and VLT/SPHERE to allow direct imaging and spectroscopy of circumstellar environments. Using a prolate apodization, the current implementations offer raw contrasts down to 10–7 at 0.2 arcsec from a star over a wide bandpass (20%), in the presence of central obstruction and struts, enabling the study of young or massive gaseous planets. Observations of older or lighter companions at smaller separations would require improvements in terms of the inner working angle (IWA) and contrast, but the methods originally used for these designs were not able to fully explore the parameter space. We propose a novel approach to improve the APLC performance. Our method relies on the linear properties of the coronagraphic electric field with the apodization at any wavelength to develop numerical solutions producing coronagraphic star images with high-contrast region in broadband light. We explore the parameter space by considering different aperture geometries, contrast levels, dark-zone sizes, bandpasses, and focal plane mask sizes. We present an application of these solutions to the case of Gemini/GPI with a design delivering a 10–8 raw contrast at 0.19 arcsec and offering a significantly reduced sensitivity to low-order aberrations compared to the current implementation. Optimal solutions have also been found to reach 10–10 contrast in broadband light regardless of the aperture shape, with effective IWA in the 2-3.5 λ/D range, therefore making the APLC a suitable option for the future exoplanet direct imagers on the ground or in space.
Convection in Oblate Solar-Type Stars

We present the first global 3D simulations of thermal convection in the oblate envelopes of rapidly-rotating solar-type stars. This has been achieved by exploiting the capabilities of the new Compressible High-ORder Unstructured Spectral difference (CHORUS) code. We consider rotation rates up to 85\% of the critical (breakup) rotation rate, which yields an equatorial radius that is up to 17\% larger than the polar radius. This substantial oblateness enhances the disparity between polar and equatorial modes of convection. We find that the convection redistributes the heat flux emitted from the outer surface, leading to an enhancement of the heat flux in the polar and equatorial regions. This finding implies that lower-mass stars with convective envelopes may not have darker equators as predicted by classical gravity darkening arguments. The vigorous high-latitude convection also establishes elongated axisymmetric circulation cells and zonal jets in the polar regions. Though the overall amplitude of the surface differential rotation, $\Delta \Omega$, is insensitive to the oblateness, the oblateness does limit the fractional kinetic energy contained in the differential rotation to no more than 61\%. Furthermore, we argue that this level of differential rotation is not enough to have a significant impact on the oblateness of the star.
Concordance and mutation

We provide a framework for studying the interplay between concordance and positive mutation and identify some of the basic structures relating the two. The fundamental result in understanding knot concordance is the structure theorem proved by Levine: for n>1 there is an isomorphism phi from the concordance group C_n of knotted (2n-1)-spheres in S^{2n+1} to an algebraically defined group G_{+-}; furthermore, G__{+-} is isomorphic to the infinite direct sum Z^infty direct sum Z_2^infty direct sum Z_4^infty. It was a startling consequence of the work of Casson and Gordon that in the classical case the kernel of phi on C_1 is infinitely generated. Beyond this, little has been discovered about the pair (C_1,phi). In this paper we present a new approach to studying C_1 by introducing a group, M, defined as the quotient of the set of knots by the equivalence relation generated by concordance and positive mutation, with group operation induced by connected sum. We prove there is a factorization of phi, C_1-->M-->G_-. Our main result is that both maps have infinitely generated kernels. Among geometric constructions on classical knots, the most subtle is positive mutation. Positive mutants are indistinguishable using classical abelian knot invariants as well as by such modern invariants as the Jones, Homfly or Kauffman polynomials. Distinguishing positive mutants up to concordance is a far more difficult problem; only one example has been known until now. The results in this paper provide, among other results, the first infinite families of knots that are distinct from their positive mutants, even up to concordance.
A Lower Bound on the Differential Entropy of Log-Concave Random Vectors with Applications.

We derive a lower bound on the differential entropy of a log-concave random variable X in terms of the p-th absolute moment of X. The new bound leads to a reverse entropy power inequality with an explicit constant, and to new bounds on the rate-distortion function and the channel capacity. Specifically, we study the rate-distortion function for log-concave sources and distortion measure d ( x , x ^ ) = | x − x ^ | r , with r ≥ 1 , and we establish that the difference between the rate-distortion function and the Shannon lower bound is at most log ( π e ) ≈ 1 . 5 bits, independently of r and the target distortion d. For mean-square error distortion, the difference is at most log ( π e 2 ) ≈ 1 bit, regardless of d. We also provide bounds on the capacity of memoryless additive noise channels when the noise is log-concave. We show that the difference between the capacity of such channels and the capacity of the Gaussian channel with the same noise power is at most log ( π e 2 ) ≈ 1 bit. Our results generalize to the case of a random vector X with possibly dependent coordinates. Our proof technique leverages tools from convex geometry.
Sampling-based methods for factored task and motion planning:

This paper presents a general-purpose formulation of a large class of discrete-time planning problems, with hybrid state and control-spaces, as factored transition systems. Factoring allows state t...
Electrically controlled Bragg resonances of an ambichiral electro-optic structure : oblique incidence

The Pockels effect can be used to tune the effective birefringence of ambichiral structures made of electro-optic materials with 42 m point group symmetry, when a dc electric field is applied parallel to the axis of nonhomogeneity. The reflectances and transmittances of such an ambichiral structure can be calculated through the solution of a boundary-value problem. The Bragg resonance peaks, for different circular-polarized-incidence conditions, blueshift as the angle of incidence increases.
Could a Local Group X-Ray Halo Affect the X-Ray and Microwave Backgrounds?

Suto et al. have suggested that an X-ray halo in the Local Group might explain both the observed low-energy excess in the X-ray background and the quadrupole anisotropy in the cosmic microwave background. Recent observations of poor groups of galaxies by the ROSAT PSPC set reasonable limits on how extensive and dense such a halo could be. The poor groups most similar to the Local Group do not have a detectable halo, and the upper limits of these observations suggest that any Local Group halo would be nearly 2 orders of magnitude too tenuous to produce the effects that Suto et al. discuss. In particular, the Sunyaev-Zeldovich effect cannot contribute significantly to the quadrupole anisotropy measured by COBE.
Time-Dependent Debye–Mie Series Solutions for Electromagnetic Scattering

Frequency domain Mie solutions to scattering from spheres have been used for a long time. However, deriving their transient analog is a challenge, as it involves an inverse Fourier transform of the spherical Hankel functions (and their derivatives) that are convolved with inverse Fourier transforms of spherical Bessel functions (and their derivatives). Series expansion of these convolutions is highly oscillatory (therefore, poorly convergent) and unstable. Indeed, the literature on numerical computation of this convolution is very sparse. In this paper, we present a novel quasi-analytical approach to compute transient Mie scattering that is both stable and rapidly convergent. The approach espoused here is to use vector tesseral harmonics as basis function for the currents in time-domain integral equations (TDIEs) together with a novel addition theorem for the Green’s functions that render these expansions stable. This procedure results in an orthogonal, spatially meshfree, and singularity-free system, giving us a set of one-dimensional (1-D) Volterra Integral equations. Time-dependent multipole coefficients for each mode are obtained via a time-marching procedure. Finally, several numerical examples are presented to show the accuracy and stability of the proposed method.
Strings and discrete fluxes of QCD

We study discrete fluxes in four dimensional SU(N) gauge theories with a mass gap by using brane compactifications which give = 1 or = 0 supersymmetry. We show that when such theories are compactified further on a torus, the t'Hooft magnetic flux m is related to the NS two-form modulus B by B = 2π(m/N). These values of B label degenerate brane vacua, giving a simple demonstration of magnetic screening. Furthermore, for these values of B one has a conventional gauge theory on a commutative torus, without having to perform any T-dualities. Because of the mass gap, a generic B does not give a four dimensional gauge theory on a non-commutative torus. The Kaluza-Klein modes which must be integrated out to give a four dimensional theory decouple only when B = 2π(m/N). Finally we show that 2π(m/N) behaves like a two form modulus of the QCD string. This confirms a previous conjecture based on properties of large N QCD suggesting a T-duality invariance.
Knowledge Grounded Conversational Symptom Detection with Graph Memory Networks

In this work, we propose a novel goal-oriented dialog task, automatic symptom detection. We build a system that can interact with patients through dialog to detect and collect clinical symptoms automatically, which can save a doctor’s time interviewing the patient. Given a set of explicit symptoms provided by the patient to initiate a dialog for diagnosing, the system is trained to collect implicit symptoms by asking questions, in order to collect more information for making an accurate diagnosis. After getting the reply from the patient for each question, the system also decides whether current information is enough for a human doctor to make a diagnosis. To achieve this goal, we propose two neural models and a training pipeline for the multi-step reasoning task. We also build a knowledge graph as additional inputs to further improve model performance. Experiments show that our model significantly outperforms the baseline by 4%, discovering 67% of implicit symptoms on average with a limited number of questions.
AutoFoley: Artificial Synthesis of Synchronized Sound Tracks for Silent Videos With Deep Learning

In movie productions, the Foley artist is responsible for creating an overlay soundtrack that helps the movie come alive for the audience. This requires the artist identify sounds that enhance the experience for the listener, reinforcing the director's intention for the scene. The artist must decide what artificial sound captures the essence of the sound and action depicted in the scene. In this paper, we present AutoFoley, an automated deep-learning tool that is used to synthesize a representative audio track for videos. AutoFoley is used to associate audio files with soundless video or to identify critical scenarios and provide a synthesized, reinforced and time-synchronized soundtrack. Our algorithm is capable of precise recognition of actions as well as interframe relations in fast- moving video clips through incorporating interpolation technique and temporal relational networks (TRN). We employ a robust multiscale recurrent neural network (RNN) and a convolutional neural network (CNN) for better understanding of the intricate input-to-output associations. To evaluate AutoFoley, we create an audio-video dataset containing a variety of sounds frequently used as Foley effects in movies. While the Foley dataset was limited to short-duration videos off the representative activities, this dataset demonstrates the capabilities of our proposed system. We show the synthesized sounds are portrayed with accurate temporal synchronization of the associated visual inputs. Human qualitative testing of AutoFoley shows more than 73% of the test subjects considered the generated soundtrack as original, which is a noteworthy improvement in comparable cross-modal research.
AN ENERGETIC MAGNETAR IN HESS J1713–381/CTB 37B

We obtained a second Chandra timing measurement of the 3.82 s pulsar CXOU J171405.7-381031 in the supernova remnant (SNR) CTB 37B, which shows that it is spinning down rapidly. The average period derivative of (5.88 {+-} 0.08) x 10{sup -11} over the 1 year time span corresponds to a dipole magnetic field strength B{sub s} = 4.8 x 10{sup 14} G, well into the magnetar range. The spin-down power E-dot = 4.2x10{sup 34} erg s{sup -1} is among the largest for magnetars, and the corresponding characteristic age {tau}{sub c{identical_to}}P/2 P-dot = 1030 years is comparable to estimates of the age of the SNR. The period derivative enables us to recover probable pulsations in an ASCA observation taken in 1996, which yields a mean characteristic age of 860 years over the longer 13 year time span. The source is well detected up to 10 keV, and its composite spectrum is typical of a magnetar. CTB 37B hosts HESS J1713-381, the first TeV source that is coincident with a magnetar. While the TeV emission has been attributed to the SNR shell, it is possibly centrally peaked, and we hypothesize that this particularly young, energetic magnetar may contribute to the HESS source. Wemore » also searched for pulsations from another source in a HESS SNR, XMMU J173203.3-344518 in HESS J1731-347/G353.6-0.7, but could not confirm pulsations or long-term flux variability, making it more likely that this source is a weakly magnetized central compact object.« less
Eating Planets for Lunch and Dinner: Signatures of Planet Consumption by Evolving Stars

Exoplanets have been observed around stars at all stages of stellar evolution, in many cases orbiting in configurations that will eventually lead to the planets being engulfed or consumed by their host stars, such as Hot Jupiters or ultra-short period planets. Furthermore, objects such as polluted white dwarfs provide strong evidence that the consumption of planets by stars is a common phenomenon. This consumption causes several significant changes in the stellar properties, such as changes to the stellar spin, luminosity, chemical composition, or mass loss processes. Here, we explore this wide variety of effects for a comprehensive range of stellar and planetary masses and stages of stellar evolution, from the main sequence over red giants to the white dwarfs. We determine that planet consumption can cause transient luminosity features that last on the order of centuries to millennia, and that the post-consumption stellar spins can often reach break-up speeds. Furthermore, stellar moss loss can be caused by this spin-up, as well as through surface grazing interactions, leading to to the formation of unusual planetary nebula shapes or collimated stellar gas ejections. Our results highlight several observable stellar features by which the presence or previous existence of a planet around a given star can be deduced. This will provide future observational campaigns with the tools to better constrain exoplanet demographics, as well as planetary formation and evolution histories.
Color transparency: Past, present and future

Abstract We review a unique prediction of Quantum Chromo Dynamics, called color transparency (CT), where the final (and/or initial) state interactions of hadrons with the nuclear medium must vanish for exclusive processes at high momentum transfers. We retrace the progress of our understanding of this phenomenon, which began with the discovery of the J / ψ meson, followed by the discovery of high energy CT phenomena, the recent developments in the investigation of the onset of CT at intermediate energies and the directions for future studies.
Current Distribution on Capacitive Electrode-Electrolyte Interfaces

The distribution of electric current on capacitive electrodes in electrolyte is of great interest in electrochemistry in general, and in bioelectronics in particular. This problem has been addressed numerically, for specific geometries; now, borrowing methods from quantum mechanics, the authors develop an analytical solution for any electrode geometry, and describe the dynamics of current redistribution from the initial equipotential boundary to a steady state where current density is proportional to capacitance per unit area. Experiment validates this theoretical result. These findings provide intriguing insights regarding innovative designs of electrodes for electroneural interfaces composed of different materials.
Fractionalization of holographic Fermi surfaces

Zero temperature states of matter at finite charge density are holographically described by a spacetime with an asymptotic electric flux. This flux can be sourced either by explicit charged matter fields in the bulk, by an extremal black hole horizon, or by a combination of the two. We refer to these as mesonic, fully fractionalized and partially fractionalized phases of matter, respectively. By coupling a charged fluid of fermions to an asymptotically AdS4 Einstein–Maxwell-dilaton theory, we exhibit quantum phase transitions between all three of these phases. The onset of fractionalization can be either a first order or continuous phase transition. In the latter case, at the quantum critical point the theory displays an emergent Lifshitz scaling symmetry in the IR.
A New Parallel Algorithm for Two-Pass Connected Component Labeling

Connected Component Labeling (CCL) is one of the most important step in pattern recognition and image processing. It assigns labels to the pixels such that adjacent pixels sharing the same features are assigned the same label. Typically, CCL requires several passes over the data. We focus on two-pass technique where each pixel is given a provisional label in the first pass whereas an actual label is assigned in the second pass. We present a scalable parallel two-pass CCL algorithm, called PAREMSP, which employs a scan strategy and the best union-find technique called REMSP, which uses REM'S algorithm for storing label equivalence information of pixels in a 2-D image. In the first pass, we divide the image among threads and each thread runs the scan phase along with REMSP simultaneously. In the second phase, we assign the final labels to the pixels. As REMSP is easily parallelizable, we use the parallel version of REMSP for merging the pixels on the boundary. Our experiments show the scalability of PAREMSP achieving speedups up to 20.1 using 24 cores on shared memory architecture using OpenMP for an image of size 465.20 MB. We find that our proposed parallel algorithm achieves linear scaling for a large resolution fixed problem size as the number of processing elements are increased. Additionally, the parallel algorithm does not make use of any hardware specific routines, and thus is highly portable.
A linear algebra approach to fast DNA mixture analysis using GPUs

Analysis of DNA samples is an important tool in forensics, and the speed of analysis can impact investigations. Comparison of DNA sequences is based on the analysis of short tandem repeats (STRs), which are short DNA sequences of 2–5 base pairs. Current forensics approaches use 20 STR loci for analysis. The use of single nucleotide polymorphisms (SNPs) has utility for analysis of complex DNA mixtures. The use of tens of thousands of SNPs loci for analysis poses significant computational challenges because the forensic analysis scales by the product of the loci count and number of DNA samples to be analyzed. In this paper, we discuss the implementation of a DNA sequence comparison algorithm by re-casting the algorithm in terms of linear algebra primitives. By developing an overloaded matrix multiplication approach to DNA comparisons, we can leverage advances in GPU hardware and algoithms for dense matrix multiplication (DGEMM) to speed up DNA sample comparisons. We show that it is possible to compare 2048 unknown DNA samples with 20 million known samples in under 6 seconds using a NVIDIA K80 GPU.