cssi/SciSciGPT-SciSciNet huggingface dataset:
Negative representation and instability in democratic elections

The challenge of understanding the collective behaviours of social systems can benefit from methods and concepts from physics1–6, not because humans are similar to electrons, but because certain large-scale behaviours can be understood without an understanding of the small-scale details7, in much the same way that sound waves can be understood without an understanding of atoms. Democratic elections are one such behaviour. Over the past few decades, physicists have explored scaling patterns in voting and the dynamics of political opinion formation (for example, see refs. 8–13). Here, we define the concepts of negative representation, in which a shift in electorate opinions produces a shift in the election outcome in the opposite direction, and electoral instability, in which an arbitrarily small change in electorate opinions can dramatically swing the election outcome, and prove that unstable elections necessarily contain negatively represented opinions. Furthermore, in the presence of low voter turnout, increasing polarization of the electorate can drive elections through a transition from a stable to an unstable regime, analogous to the phase transition by which some materials become ferromagnetic below their critical temperatures. Empirical data suggest that the United States’ presidential elections underwent such a phase transition in the 1970s and have since become increasingly unstable. In a mathematical model of democratic elections, electoral instability is shown to be linked to negative representation, which occurs when a shift in electoral opinions pushes the election outcome in the opposite direction.
Finite temperature effects in the supergravity dual of the N = 1* gauge theory

We consider the supergravity dual of the = 1* theory at finite temperature by applying the Polchinski-Strassler construction to the black D3-brane solution of type-IIB supergravity. At finite temperature the 5-brane probe action is minimized when the probe falls to the horizon, although metastable minima with r >> rH persist for a range of temperatures. Thermal effects on the 3-form source for the chiral multiplet mass m and its order m2 back reaction on the other fields of the IIB theory are computed. We find unique solutions which are regular at the horizon and have the correct behavior on the boundary. For fixed temperature T, the horizon shrinks for increasing m2 suggesting that there is a critical temperature separating the system into high and low temperature phases. In the high temperature phase 5-branes are unnecessary since there are no naked singularities. Using the order m2 correction to the horizon area we calculate the correction to the entropy to be Δ = −0.1714N2m2T, which is less than the free field result.
Beacons In the Dark: Using Novae and Supernovae to Detect Dwarf Galaxies in the Local Universe

© 2015. The American Astronomical Society. All rights reserved. We propose that luminous transients, including novae and supernovae (SNe), can be used to detect the faintest galaxies in the universe. Beyond a few megaparsecs, dwarf galaxies with stellar masses ≲106 M ⊙ will likely be too faint and/or too low in surface brightness to be directly detected in upcoming large area ground-based photometric surveys. However, single-epoch Large Synoptic Survey Telescope photometry will be able to detect novae to distances of ∼30 Mpc and SNe to gigaparsec-scale distances. Depending on the form of the stellar mass.halo mass relation and the underlying star formation histories of low-mass dwarfs, the expected nova rates will be a few to ∼100 yr-1 and the expected SN rates (including both type Ia and core-collapse) will be ∼102.104within the observable (4 sr) volume. The transient rate associated with intrahalo stars will be comparably large, but these transients will be located close to bright galaxies, in contrast to the dwarfs, which should trace the underlying largescale structure of the cosmic web. Aggressive follow-up of hostless transients has the potential to uncover the predicted enormous population of low-mass field dwarf galaxies.
Semiclassical Boltzmann theory of spin Hall effects in giant Rashba systems

For the spin Hall effect arising from strong band-structure spin–orbit coupling, a semiclassical Boltzmann theory reasonably addressing the intriguing disorder effect called side-jump has not yet been developed. This paper describes such a theory in which the key ingredient is the spin-current counterpart of the semiclassical side-jump velocity (introduced in the context of the anomalous Hall effect). Applying this theory to spin Hall effects in a two-dimensional electron gas with giant Rashba spin–orbit coupling, largely enhanced spin Hall angle is found in the presence of magnetic impurities when only the lower Rashba band is partially occupied.
Boundary Value Problems for the Stationary Axisymmetric Einstein Equations: A Disk Rotating Around a Black Hole

We solve a class of boundary value problems for the stationary axisymmetric Einstein equations involving a disk rotating around a central black hole. The solutions are given explicitly in terms of theta functions on a family of hyperelliptic Riemann surfaces of genus 4. In the absence of a disk, they reduce to the Kerr black hole. In the absence of a black hole, they reduce to the Neugebauer-Meinel disk.
DEVELOPING ATMOSPHERIC RETRIEVAL METHODS FOR DIRECT IMAGING SPECTROSCOPY OF GAS GIANTS IN REFLECTED LIGHT. I. METHANE ABUNDANCES AND BASIC CLOUD PROPERTIES

Reflected light spectroscopy and photometry of cool, directly imaged extrasolar giant planets are expected to be performed in the next decade by space-based telescopes equipped with optical wavelength coronagraphs and integral field spectrographs, such as the Wide-Field Infrared Survey Telescope (WFIRST). We are developing a new atmospheric retrieval methodology to help assess the science return and inform the instrument design for such future missions, and ultimately interpret the resulting observations. Our retrieval technique employs an albedo model coupled with both a Markov chain Monte Carlo Ensemble Sampler (emcee) and a multimodal nested sampling algorithm (MultiNest) to map the posterior distribution. This combination makes the global evidence calculation more robust for any given model, and highlights possible discrepancies in the likelihood maps. Here we apply this methodology to simulated spectra of cool giant planets. As a proof-of-concept, our current atmospheric model contains 1 or 2 cloud layers, methane as a major absorber, and a H2-He background gas. This 6-to-9 parameter model is appropriate for Jupiter-like planets and can be easily expanded in the future. In addition to deriving the marginal likelihood distribution and confidence intervals for the model parameters, we perform model selection to determine the significance of methane and cloud detection as a function of expected signal-to-noise, in the presence of spectral noise correlations. After internal validation, the method is applied to realistic reflected-light spectra of Jupiter, Saturn, and HD 99492 c, a likely observing target. We find that the presence or absence of clouds and methane can be determined with high accuracy, while parameters uncertainties are model-dependent.
Model-Robust Regression and a Bayesian `Sandwich' Estimator

We present a new Bayesian approach to model-robust linear regression that leads to uncertainty estimates with the same robustness properties as the Huber–White sandwich estimator. The sandwich estimator is known to provide asymptotically correct frequentist inference, even when standard modeling assumptions such as linearity and homoscedasticity in the data-generating mechanism are violated. Our derivation provides a compelling Bayesian justification for using this simple and popular tool, and it also clarifies what is being estimated when the data-generating mechanism is not linear. We demonstrate the applicability of our approach using a simulation study and health care cost data from an evaluation of the Washington State Basic Health Plan.
On the universality of the entropy-area relation

We present an argument that for a large class of possible dynamics, a canonical quantization of gravity will satisfy the Bekenstein–Hawking entropy–area relation. This result holds for temperatures low compared to the Planck temperature and for boundaries with areas large compared to the Planck area. We also relate our description, in terms of a grand canonical ensemble, to previous geometric entropy calculations using area ensembles.
Inverse anisotropic conductivity from internal current densities

This paper concerns the reconstruction of a fully anisotropic conductivity tensor γ from internal current densities of the form J = γ∇u, where u solves a second-order elliptic equation ∇ (γ∇u) = 0 on a bounded domain X with prescribed boundary conditions. A minimum number of n + 2 such functionals known on Y⊂X, where n is the spatial dimension, is sufficient to guarantee a unique and explicit reconstruction of γ locally on Y. Moreover, we show that γ is reconstructed with a loss of one derivative compared to errors in the measurement of J in the general case and no loss of derivatives in the special case where γ is scalar. We also describe linear combinations of mixed partial derivatives of γ that exhibit better stability properties and hence can be reconstructed with better resolution in practice.
Swimming Against The Tide: Gender Bias In The Physics Classroom

This study examines physics students' evaluations of identical, video-recorded lectures performed by female and male actors playing the role of professors. The results indicate that evaluations by male students show statistically significant overall biases with male professors rated more positively than female professors. Female students tended to be egalitarian, except in two areas. Female students evaluated female professors' interpersonal/communicative skills more positively than male professors'. They evaluated female professors' scientific knowledge and skills less positively than that of male professors just as male students did. These findings are relevant to two areas of research on bias in evaluation: rater-ratee similarity bias and stereotype confirmation bias. Results from this study have important implications for efforts focused on educating students and mentoring faculty members in order to increase the representation of women in the physical sciences.
Topological phases: Classification of topological insulators and superconductors of non-interacting Fermions, and beyond

After briefly recalling the quantum entanglement-based view of topological phases of matter in order to outline the general context, we give an overview of different approaches to the classification problem of topological insulators and superconductors of non-interacting fermions. In particular, we review in some detail general symmetry aspects of the 'ten-fold way' which forms the foundation of the classification, and put different approaches to the classification in relationship with each other. We end by briefly mentioning some of the results obtained on the effect of interactions, mainly in three spatial dimensions.
Measuring Galactic Extinction: A Test

We test the recently published all-sky reddening map of Schlegel, Finkbeiner, & Davis (hereafter SFD) using the extinction study of a region in the Taurus dark cloud complex by Arce & Goodman (hereafter AG). In their study, AG use four different techniques to measure the amount and structure of the extinction toward Taurus, and all four techniques agree very well. Thus, we believe that the AG results are a truthful representation of the extinction in the region and can be used to test the reliability of the SFD reddening map. The results of our test show that the SFD all-sky reddening map, which is based on data from COBE/DIRBE and IRAS/ISSA, overestimates the reddening by a factor of 1.3-1.5 in regions of smooth extinction with AV > 0.5 mag. In some regions of steep extinction gradients, the SFD map underestimates the reddening value, probably because of its low spatial resolution. We expect that the astronomical community will be using the SFD reddening map extensively. We offer this Letter as a cautionary note about using the SFD map in regions of high extinction (AV > 0.5 mag), since it might not be giving accurate reddening values there.
PREPOTENTIALS FOR (2, 2) SUPERGRAVITY

We present a complete solution to the constraints for two-dimensional N = 2 supergravity in N = 2 superspace. We obtain explicit expressions for the covariant derivatives in terms of the vector superfield Hm and, for the two versions of minimal (2,2) supergravity, a chiral or twisted chiral scalar superfield ϕ.
NEPTUNE ON TIPTOES: DYNAMICAL HISTORIES THAT PRESERVE THE COLD CLASSICAL KUIPER BELT

The current dynamical structure of the Kuiper Belt was shaped by the orbital evolution of the giant planets, especially Neptune, during the era following planet formation when the giant planets may have undergone planet-planet scattering and/or planetesimal-driven migration. Numerical simulations of this process, while reproducing many properties of the Belt, fail to generate the high inclinations and eccentricities observed for some objects while maintaining the observed dynamically 'cold' population. We present the first of a three-part parameter study of how different dynamical histories of Neptune sculpt the planetesimal disk. Here we identify which dynamical histories allow an in situ planetesimal disk to remain dynamically cold, becoming today's cold Kuiper Belt population. We find that if Neptune undergoes a period of elevated eccentricity and/or inclination, it secularly excites the eccentricities and inclinations of the planetesimal disk. We demonstrate that there are several well-defined regimes for this secular excitation, depending on the relative timescales of Neptune's migration, the damping of Neptune's orbital inclination and/or eccentricity, and the secular evolution of the planetesimals. We model this secular excitation analytically in each regime, allowing for a thorough exploration of parameter space. Neptune's eccentricity and inclination can remain high for a limited amount of timemore » without disrupting the cold classical belt. In the regime of slow damping and slow migration, if Neptune is located (for example) at 20 AU, then its eccentricity must stay below 0.18 and its inclination below 6 Degree-Sign .« less
On Representational Redundancy, Surplus Structure, and the Hole Argument

We address a recent proposal concerning 'surplus structure' due to Nguyen et al. ['Why Surplus Structure is Not Superfluous.' Br. J. Phi. Sci. Forthcoming.] We argue that the sense of 'surplus structure' captured by their formal criterion is importantly different from---and in a sense, opposite to---another sense of 'surplus structure' used by philosophers. We argue that minimizing structure in one sense is generally incompatible with minimizing structure in the other sense. We then show how these distinctions bear on Nguyen et al.'s arguments about Yang-Mills theory and on the hole argument.
Generalized mode-coupling theory of the glass transition: schematic results at finite and infinite order

We present an extensive treatment of the generalized mode-coupling theory (GMCT) of the glass transition, which seeks to describe the dynamics of glass-forming liquids using only static structural information as input. This theory amounts to an infinite hierarchy of coupled equations for multi-point density correlations, the lowest-order closure of which is equivalent to standard mode-coupling theory. Here we focus on simplified schematic GMCT hierarchies, which lack any explicit wavevector-dependence and therefore allow for greater analytical and numerical tractability. For one particular schematic model, we derive the unique analytic solution of the infinite hierarchy, and demonstrate that closing the hierarchy at finite order leads to uniform convergence as the closure level increases. We also show numerically that a similarly robust convergence pattern emerges for more generic schematic GMCT models, suggesting that the GMCT framework is generally convergent, even though no small parameter exists in the theory. Finally, we discuss how different effective weights on the high-order contributions ultimately control whether the transition is continuous, discontinuous, or strictly avoided, providing new means to relate structure to dynamics in glass-forming systems.
Fermionic mapping for eigenvalue correlation functions of weakly non-Hermitian symplectic ensemble

Abstract The eigenvalues of an arbitrary quaternionic matrix have a joint probability distribution function first derived by Ginibre. We derive the j.p.d. for the weakly non-Hermitian version of this problem and then show that there exists a mapping of this system onto a fermionic field theory. This mapping is used to integrate over the positions of the eigenvalues and obtain eigenvalue density as well as all higher correlation functions for both the strongly and weakly non-Hermitian cases.
Semidefinite Descriptions of the Convex Hull of Rotation Matrices

We study the convex hull of $SO(n)$, the set of $n\times n$ orthogonal matrices with unit determinant, from the point of view of semidefinite programming. We show that the convex hull of $SO(n)$ is doubly spectrahedral, i.e., both it and its polar have a description as the intersection of a cone of positive semidefinite matrices with an affine subspace. Our spectrahedral representations are explicit and are of minimum size, in the sense that there are no smaller spectrahedral representations of these convex bodies.
Most Likely Optimal Subsampled Markov Chain Monte Carlo

Markov Chain Monte Carlo (MCMC) requires to evaluate the full data likelihood at different parameter values iteratively and is often computationally infeasible for large data sets. This paper proposes to approximate the log-likelihood with subsamples taken according to nonuniform subsampling probabilities, and derives the most likely optimal (MLO) subsampling probabilities for better approximation. Compared with existing subsampled MCMC algorithm with equal subsampling probabilities, the MLO subsampled MCMC has a higher estimation efficiency with the same subsampling ratio. The authors also derive a formula using the asymptotic distribution of the subsampled log-likelihood to determine the required subsample size in each MCMC iteration for a given level of precision. This formula is used to develop an adaptive version of the MLO subsampled MCMC algorithm. Numerical experiments demonstrate that the proposed method outperforms the uniform subsampled MCMC.
FUSION03, Concluding Remarks

Fusion reactions below the Coulomb barrier provide new insights into multidimensional quantum tunneling, nuclear reaction dynamics and nuclear structure. These reactions are also of considerable interest to nuclear astrophysics. In this summary recent developments in the field are reviewed and open questions related to subbarrier fusion are presented.
Comparison of one-dimensional and quasi-one-dimensional Hubbard models from the variational two-electron reduced-density-matrix method

Minimizing the energy of an \(N\)-electron system as a functional of a two-electron reduced density matrix (2-RDM), constrained by necessary \(N\)-representability conditions (conditions for the 2-RDM to represent an ensemble \(N\)-electron quantum system), yields a rigorous lower bound to the ground-state energy in contrast to variational wave function methods. We characterize the performance of two sets of approximate constraints, (2,2)-positivity (DQG) and approximate (2,3)-positivity (DQGT) conditions, at capturing correlation in one-dimensional and quasi-one-dimensional (ladder) Hubbard models. We find that, while both the DQG and DQGT conditions capture both the weak and strong correlation limits, the more stringent DQGT conditions improve the ground-state energies, the natural occupation numbers, the pair correlation function, the effective hopping, and the connected (cumulant) part of the 2-RDM. We observe that the DQGT conditions are effective at capturing strong electron correlation effects in both one- and quasi-one-dimensional lattices for both half filling and less-than-half filling.
On a Stringy Singular Cohomology

String theory has already motivated, suggested, and sometimes well-nigh proved a number of interesting and sometimes unexpected mathematical results, such as mirror symmetry. A careful examination of the behavior of string propagation on (mildly) singular varieties similarly suggests a new type of (co)homology theory. It has the "good behavior" of the well-established intersection (co)homology and L2-cohomology, but is markedly different in some aspects. For one, unlike the intersection (co)homology and the L2-cohomology (or any other known thus far), this new cohomology is symmetric with respect to the mirror map. Among the available choices, this makes it into a prime candidate for describing the string theory zero modes in geometrical terms.
Intensity Mapping of Molecular Gas During Cosmic Reionization

I present a simple calculation of the expected mean CO brightness temperature from the large-scale distribution of galaxies during cosmic reionization. The calculation is based on the cosmic star formation rate density required to reionize, and keep ionized, the intergalactic medium, and uses standard relationships between star formation rate, IR luminosity, and CO luminosity derived for star-forming galaxies over a wide range in redshift. I find that the mean CO brightness temperature resulting from the galaxies that could reionize the universe at z = 8 is T_B ∼ 1.1(C/5)(fesc/0.1)−1μK, where fesc is the escape fraction of ionizing photons from the first galaxies and C is the IGM clumping factor. Intensity mapping of the CO emission from the large-scale structure of the star-forming galaxies during cosmic reionization on scales of order 102 to 103 deg^2, in combination with H i 21 cm imaging of the neutral IGM, will provide a comprehensive study of the earliest epoch of galaxy formation.
Achieving algorithmic resilience for temporal integration through spectral deferred corrections

Author(s): Grout, RW; Kolla, H; Minion, ML; Bell, JB | Abstract: Spectral deferred corrections (SDC) is an iterative approach for constructing higher-order-accurate numerical approximations of ordinary differential equations. SDC starts with an initial approximation of the solution defined at a set of Gaussian or spectral collocation nodes over a time interval and uses an iterative application of lower-order time discretizations applied to a correction equation to improve the solution at these nodes. Each deferred correction sweep increases the formal order of accuracy of the method up to the limit inherent in the accuracy defined by the collocation points. In this paper, we demonstrate that SDC is well suited to recovering from soft (transient) hardware faults in the data. A strategy where extra correction iterations are used to recover from soft errors and provide algorithmic resilience is proposed. Specifically, in this approach the iteration is continued until the residual (a measure of the error in the approximation) is small relative to the residual of the first correction iteration and changes slowly between successive iterations. We demonstrate the effectiveness of this strategy for both canonical test problems and a comprehensive situation involving a mature scientific application code that solves the reacting Navier-Stokes equations for combustion research.
A RESOLVED CENSUS OF MILLIMETER EMISSION FROM TAURUS MULTIPLE STAR SYSTEMS

We present a high angular resolution millimeter-wave dust continuum imaging survey of circumstellar material associated with the individual components of 23 multiple star systems in the Taurus-Auriga young cluster. Combined with previous measurements in the literature, these new data permit a comprehensive look at how the millimeter luminosity (a rough tracer of disk mass) relates to the separation and mass of a stellar companion. Approximately one-third (28%-37%) of the individual stars in multiple systems have detectable millimeter emission, an incidence rate half that for single stars (~62%) which does not depend on the number of companions. There is a strong, positive correlation between the luminosity and projected separation (ap ) of a stellar pair. Wide pairs (ap > 300 AU) have a similar luminosity distribution as single stars, medium pairs (ap 30-300 AU) are a factor of five fainter, and close pairs (ap < 30 AU) are ~5× fainter yet (aside from a small, but notable population of bright circumbinary disks). In most cases, the emission is dominated by a disk around the primary (or a wide tertiary in hierarchical triples), but there is no clear relationship between luminosity and stellar mass ratio. A direct comparison of resolved disk sizes with predictions from tidal truncation models yields mixed results; some disks are much larger than expected given the projected distances of their companions. We suggest that the presence of a stellar companion impacts disk properties at a level comparable to the internal evolution mechanisms that operate in an isolated system, with both the multiple star formation process itself and star-disk tidal interactions likely playing important roles in the evolution of circumstellar material. From the perspective of the mass content of the disk reservoir, we expect that (giant) planet formation is inhibited around the components of close pairs or secondaries, but should be as likely as for single stars around the primaries (or wide tertiaries in hierarchical triples) in more widely separated multiple star systems.
A Relativistic Wave Equation for the Skyrmion

Abstract We propose a relativistically invariant wave equation for the Skyrme soliton. It is a differential equation on the space R 1 , 3 × S 3 which is invariant under the Lorentz group and isospin. The internal variable valued in SU ( 2 ) ≡ S 3 describes the orientation of the soliton. The mass of a particle of spin and isospin both equal to j = 1 2 , 3 2 … is predicted to be M = m 1 + K 2 j ( j + 1 ) 1 + K 1 j ( j + 1 ) which agrees with the known spectrum for low angular momentum. The iso-scalar magnetic moment is predicted to be - K 1 4 m Σ , where Σ is the spin.
SLoWPoKES-II: 100,000 Wide Binaries Identified in SDSS without Proper Motions

We present the SLoWPoKES-II catalog of low-mass visual binaries identified from the Sloan Digital Sky Survey by matching photometric distances. The candidate pairs are vetted by comparing the stellar density at their respective Galactic positions to Monte Carlo realizations of a simulated Milky Way. In this way, we are able to identify large numbers of bona fide wide binaries without the need of proper motions. 105,537 visual binaries with angular separations of $\sim$1-20", are identified, each with a probability of chance alignment of $\lesssim$5%. This is the largest catalog of bona fide wide binaries to date, and it contains a diversity of systems---in mass, mass ratios, binary separations, metallicity, and evolutionary states---that should facilitate follow-up studies to characterize the properties of M dwarfs and white dwarfs. There is a subtle but definitive suggestion of multiple populations in the physical separation distribution, supporting earlier findings. We suggest that wide binaries are comprised of multiple populations, most likely representing different formation modes. There are 141 M7 or later wide binary candidates, representing a 7-fold increase in the number currently known. These binaries are too wide to have been formed via the ejection mechanism. Finally, we find that ~6% of spectroscopically confirmed M dwarfs are not included in the SDSS STAR catalog; they are misclassified as extended sources due to the presence of a nearby or partially resolved companion. The SLoWPoKES-II catalog is publicly available to the entire community on the world wide web via the Filtergraph data visualization portal.
Type Ia supernovae, evolution, and the cosmological constant

We explore the possible role of evolution in the analysis of data on Type Ia supernovae (SNe Ia) at cosmological distances. First, using a variety of simple sleuthing techniques, we find evidence that the properties of the high- and low-redshift SNe Ia observed so far differ from one another. Next, we examine the effects of allowing for an uncertain amount of evolution in the analysis, using two simple phenomenological models for evolution and prior probabilities that express a preference for no evolution but allow it to be present. One model shifts the magnitudes of the high-redshift SNe Ia relative to the low-redshift SNe Ia by a fixed amount. A second, more realistic, model introduces a continuous magnitude shift of the form δm(z) = β ln(1 + z) to the SNe Ia sample. The result is that cosmological models and evolution are highly degenerate with one another, so that the incorporation of even very simple models for evolution makes it virtually impossible to pin down the values of ΩM and ΩΛ, the density parameters for nonrelativistic matter and for the cosmological constant, respectively. The Hubble constant, H0, is unaffected by evolution. We evaluate the Bayes factor for models with evolution versus models without evolution, which, if one has no prior predilection for or against evolution, is the odds ratio for these two classes of models. The resulting values are always of order 1, in spite of the fact that the models that include evolution have additional parameters; thus, the data alone cannot discriminate between the two possibilities. Simulations show that simply acquiring more data of the same type as are available now will not alleviate the difficulty of separating evolution from cosmology in the analysis. What is needed is a better physical understanding of the SN Ia process, and the connections among the maximum luminosity, rate of decline, spectra, and initial conditions, so that physical models for evolution may be constructed, and confronted with the data. Moreover, we show that if SNe Ia evolve with time, but evolution is neglected in analyzing data, then, given enough SNe Ia, the analysis hones in on values of ΩM and ΩΛ that are incorrect. Using Bayesian methods, we show that the probability that the cosmological constant is nonzero (rather than zero) is unchanged by the SNe Ia data when one accounts for the possibility of evolution, provided that we do not discriminate among open, closed, and flat cosmologies a priori. The case for nonzero cosmological constant is stronger if the universe is presumed to be flat but still depends sensitively on the degree to which the peak luminosities of SNe Ia evolve as a function of redshift.
Low-energy Kähler potentials in supersymmetric gauge theories with (almost) flat directions

Abstract We derive the supersymmetric low-energy effective theory of the D-flat directions of a supersymmetric gauge theory. The Kahler potential of Affleck, Dine and Seiberg is derived by applying holomorphic constraints which manifestly maintain supersymmetry. We also present a simple procedure for calculating all derivatives of the Kahler potential at points on the flat direction manifold. Together with knowledge of the superpotential, these are sufficient for a complete determination of the spectrum and the interactions of the light degrees of freedom. We illustrate the method on the example of a chiral abelian model, and comment on its application to more complicated calculable models with dynamical supersymmetry breaking.
The Role of Magnetic Fields in Starburst Galaxies as Revealed by OH Megamasers

We present estimates of magnetic field strengths in the interstellar media of starburst galaxies derived from measurements of Zeeman splitting associated with OH megamasers. The results for eight galaxies with Zeeman detections suggest that the magnetic energy density in the interstellar medium of starburst galaxies is comparable to their hydrostatic gas pressure, as in the Milky Way. We discuss the significant uncertainties in this conclusion, and possible measurements that could reduce these uncertainties. We also compare the Zeeman splitting derived magnetic field estimates to magnetic field strengths estimated using synchrotron fluxes and assuming that the magnetic field and cosmic rays have comparable energy densities, known as the "minimum energy" argument. We find that the minimum energy argument systematically underestimates magnetic fields in starburst galaxies, and that the conditions that would be required to produce agreement between the minimum energy estimate and the Zeeman derived estimate of interstellar medium magnetic fields are implausible. The conclusion that magnetic fields in starburst galaxies exceed the minimum energy magnetic fields is consistent with starburst galaxies adhering to the linearity of the far-infrared-radio correlation.
Privacy-Preserving Eye Videos using Rubber Sheet Model

Video-based eye trackers estimate gaze based on eye images/videos. As security and privacy concerns loom over technological advancements, tackling such challenges is crucial. We present a new approach to handle privacy issues in eye videos by replacing the current identifiable iris texture with a different iris template in the video capture pipeline based on the Rubber Sheet Model. We extend to image blending and median-value representations to demonstrate that videos can be manipulated without significantly degrading segmentation and pupil detection accuracy.
Perspective: Geometrically frustrated assemblies

This perspective will overview an emerging paradigm for self-organized soft materials, geometrically frustrated assemblies, where interactions between self-assembling elements (e.g., particles, macromolecules, proteins) favor local packing motifs that are incompatible with uniform global order in the assembly. This classification applies to a broad range of material assemblies including self-twisting protein filament bundles, amyloid fibers, chiral smectics and membranes, particle-coated droplets, curved protein shells, and phase-separated lipid vesicles. In assemblies, geometric frustration leads to a host of anomalous structural and thermodynamic properties, including heterogeneous and internally stressed equilibrium structures, self-limiting assembly, and topological defects in the equilibrium assembly structures. The purpose of this perspective is to (1) highlight the unifying principles and consequences of geometric frustration in soft matter assemblies; (2) classify the known distinct modes of frust...
First- and Second-Order Asymptotics in Covert Communication

We study the first- and second-order asymptotics of covert communication over binary-input discrete memoryless channels for three different covertness metrics and under maximum probability of error constraint. When covertness is measured in terms of the relative entropy between the channel output distributions induced with and without communication, we characterize the exact first- and second-order asymptotics of the number of bits that can be reliably transmitted with a maximum probability of error less than $\epsilon $ and a relative entropy less than $\delta $ . When covertness is measured in terms of the variational distance between the channel output distributions or in terms of the probability of missed detection for fixed probability of false alarm, we establish the exact first-order asymptotics and bound the second-order asymptotics. Pulse position modulation achieves the optimal first-order asymptotics for all three metrics, as well as the optimal second-order asymptotics for relative entropy. The main conceptual contribution of this paper is to clarify how the choice of a covertness metric impacts the information-theoretic limits of covert communications. The main technical contribution underlying our results is a detailed expurgation argument to show the existence of a code satisfying the reliability and covertness criteria.
Computing upper cluster algebras

This paper develops techniques for producing presentations of upper cluster algebras. These techniques are suited to computer implementation, and will always succeed when the upper cluster algebra is totally coprime and finitely generated. We include several examples of presentations produced by these methods.
The Nature of Active Galactic Nuclei with Velocity Offset Emission Lines

We obtained Keck/OSIRIS near-IR adaptive optics-assisted integral-field spectroscopy to probe the morphology and kinematics of the ionized gas in four velocity-offset active galactic nuclei (AGNs) from the Sloan Digital Sky Survey. These objects possess optical emission lines that are offset in velocity from systemic as measured from stellar absorption features. At a resolution of ~0".18, OSIRIS allows us to distinguish which velocity offset emission lines are produced by the motion of an AGN in a dual supermassive black hole system, and which are produced by outflows or other kinematic structures. In three galaxies, J1018+2941, J1055+1520, and J1346+5228, the spectral offset of the emission lines is caused by AGN-driven outflows. In the remaining galaxy, J1117+6140, a counterrotating nuclear disk is observed that contains the peak of Paα emission 0".2 from the center of the galaxy. The most plausible explanation for the origin of this spatially and kinematically offset peak is that it is a region of enhanced Paα emission located at the intersection zone between the nuclear disk and the bar of the galaxy. In all four objects, the peak of ionized gas emission is not spatially coincident with the center of the galaxy as traced by the peak of the near-IR continuum emission. The peaks of ionized gas emission are spatially offset from the galaxy centers by 0".1–0".4 (0.1–0.7 kpc). We find that the velocity offset originates at the location of this peak of emission, and the value of the offset can be directly measured in the velocity maps. The emission-line ratios of these four velocity-offset AGNs can be reproduced only with a mixture of shocks and AGN photoionization. Shocks provide a natural explanation for the origin of the spatially and spectrally offset peaks of ionized gas emission in these galaxies.
Reevaluating Adversarial Examples in Natural Language.

State-of-the-art attacks on NLP models lack a shared definition of a what constitutes a successful attack. We distill ideas from past work into a unified framework: a successful natural language adversarial example is a perturbation that fools the model and follows some linguistic constraints. We then analyze the outputs of two state-of-the-art synonym substitution attacks. We find that their perturbations often do not preserve semantics, and 38% introduce grammatical errors. Human surveys reveal that to successfully preserve semantics, we need to significantly increase the minimum cosine similarities between the embeddings of swapped words and between the sentence encodings of original and perturbed sentences.With constraints adjusted to better preserve semantics and grammaticality, the attack success rate drops by over 70 percentage points.
Reconciling Observed and Simulated Stellar Halo Masses

We use cosmological hydrodynamical simulations of Milky Way–mass galaxies from the FIRE project to evaluate various strategies for estimating the mass of a galaxy's stellar halo from deep, integrated-light images. We find good agreement with integrated-light observations if we mimic observational methods to measure the mass of the stellar halo by selecting regions of an image via projected radius relative to the disk scale length or by their surface density in stellar mass. However, these observational methods systematically underestimate the accreted stellar component, defined in our (and most) simulations as the mass of stars formed outside of the host galaxy, by up to a factor of 10, since the accreted component is centrally concentrated and therefore substantially obscured by the galactic disk. Furthermore, these observational methods introduce spurious dependencies of the estimated accreted stellar component on the stellar mass and size of galaxies that can obscure the trends in accreted stellar mass predicted by cosmological simulations, since we find that in our simulations, the size and shape of the central galaxy are not strongly correlated with the assembly history of the accreted stellar halo. This effect persists whether galaxies are viewed edge-on or face-on. We show that metallicity or color information may provide a way to more cleanly delineate in observations the regions dominated by accreted stars. Absent additional data, we caution that estimates of the mass of the accreted stellar component from single-band images alone should be taken as lower limits.
The Post-Starburst Evolution of Tidal Disruption Event Host Galaxies

NSF [DGE-1143953, AST-0908280]; PEO; ARCS Phoenix Chapter and Burton Family; NASA through the Einstein Fellowship Program [PF6-170148]; NASA [ADP-NNX10AE88G]; Alfred P. Sloan Foundation; National Science Foundation; U.S. Department of Energy Office of Science; University of Arizona; Brazilian Participation Group; Brookhaven National Laboratory; Carnegie Mellon University; niversity of Florida; French Participation Group; German Participation Group; Harvard University; Instituto de Astrofisica de Canarias; Michigan State/Notre Dame/JINA Participation Group; Johns Hopkins University; Lawrence Berkeley National Laboratory; Max Planck Institute for Astrophysics; Max Planck Institute for Extraterrestrial Physics; New Mexico State University; New York University; Ohio State University; Pennsylvania State University; University of Portsmouth; Princeton University; Spanish Participation Group; University of Tokyo, University of Utah; Vanderbilt University; University of Virginia; University of Washington; Yale University
Peak criterion for choosing Gaussian kernel bandwidth in Support Vector Data Description

Support Vector Data Description (SVDD) is a machine learning technique used for single class classification and outlier detection. SVDD formulation with kernel function provides a flexible boundary around data. The value of kernel function parameters affects the nature of data boundary. For example, it is observed that with Gaussian kernel, as the value of kernel bandwidth is lowered, the data boundary changes from spherical to wiggly. The spherical data boundary leads to underfitting and extremely wiggly data boundary leads to overfitting. In this paper we propose an empirical criteria to obtain a good value of Gaussian kernel bandwidth which provides a smooth boundary capturing the essential visual features of the data.
Fundamental Parameters of Kepler Eclipsing Binaries. I. KIC 5738698

Eclipsing binaries serve as a valuable source of stellar masses and radii that inform stellar evolutionary models and provide insight into additional astrophysical processes. The exquisite light curves generated by space-based missions such as Kepler offer the most stringent tests to date. We use the Kepler light curve of the 4.8-day eclipsing binary KIC 5739896 with ground based optical spectra to derive fundamental parameters for the system. We reconstruct the component spectra to determine the individual atmospheric parameters, and model the Kepler photometry with the binary synthesis code ELC to obtain accurate masses and radii. The two components of KIC 5738698 are F-type stars with M1 = 1.39+/-0.04M, M2 = 1.34+/-0.06M, and R1 = 1.84+/-0.03R, R2 = 1.72+/-0.03R. We also report a small eccentricity (e < 0.0017) and unusual albedo values that are required to match the detailed shape of the Kepler light curve. Comparisons with evolutionary models indicate an approximate age of 2.3 Gyr for the system.
ELECTRON INJECTION BY WHISTLER WAVES IN NON-RELATIVISTIC SHOCKS

Electron acceleration to non-thermal, ultra-relativistic energies (~10-100 TeV) is revealed by radio and X-ray observations of shocks in young supernova remnants (SNRs). The diffusive shock acceleration (DSA) mechanism is usually invoked to explain this acceleration, but the way in which electrons are initially energized or "injected" into this acceleration process starting from thermal energies is an unresolved problem. In this paper we study the initial acceleration of electrons in non-relativistic shocks from first principles, using two- and three-dimensional particle-in-cell (PIC) plasma simulations. We systematically explore the space of shock parameters (the Alfvenic Mach number, MA , the shock velocity, v sh, the angle between the upstream magnetic field and the shock normal, θ Bn , and the ion to electron mass ratio, mi /me ). We find that significant non-thermal acceleration occurs due to the growth of oblique whistler waves in the foot of quasi-perpendicular shocks. This acceleration strongly depends on using fairly large numerical mass ratios, mi /me , which may explain why it had not been observed in previous PIC simulations of this problem. The obtained electron energy distributions show power-law tails with spectral indices up to α ~ 3-4. The maximum energies of the accelerated particles are consistent with the electron Larmor radii being comparable to that of the ions, indicating potential injection into the subsequent DSA process. This injection mechanism, however, requires the shock waves to have fairly low Alfenic Mach numbers, MA 20, which is consistent with the theoretical conditions for the growth of whistler waves in the shock foot (MA (mi /me )1/2). Thus, if the whistler mechanism is the only robust electron injection process at work in SNR shocks, then SNRs that display non-thermal emission must have significantly amplified upstream magnetic fields. Such field amplification is likely achieved by the escaping cosmic rays, so electron and proton acceleration in SNR shocks must be interconnected.
The Spectral Energy Distributions of Narrow-Line Seyfert 1 Galaxies

Narrow-line Seyfert 1 galaxies are identified by their uniform optical spectral properties. Studies of samples of NLSls reveal, however, a range of X-ray spectral and variability behavior, and UV spectral behavior. We describe the range of behavior observed, illustrating with a comparison of the XMM-Newton and HST data from the NLS1s 1H 0707-495 and Ton S180, and discuss how the spectral energy distribution may causally link the UV and X-ray properties.
Brane waves and strings

Abstract Recently, solutions of the Born-Infeld theory representing strings emanating from a Dirichlet p-brane have been constructed. We discuss the embedding of these Bom-Infeld solutions into the non-abelian theory appropriate to multiple overlapping p-branes. We also prove supersymmetry of the solutions explicitly in the full non-linear theory. We then study transverse fluctuations, both from the world-brane point of view and by analyzing a test string in the supergravity background of a Dp-brane. We find agreement between the two approaches for the cases p = 3,4.