cssi/SciSciGPT-SciSciNet huggingface dataset:
Spinor-unit field representation of electromagnetism applied to a model inflationary cosmology

The new spinor-unit field representation of the electromagnetism (Nash in J Math Phys 51:042501-1–042501-27, 2010) (with quark and lepton sources) is integrated via minimal coupling with standard Einstein gravitation, to formulate a Lagrangian model of the very early universe. A completely new solution to the coupled Einstein–Maxwell equations, with sources, is derived. These equations are generalized somewhat, but not in a way that violates any physical principles. The solution of the coupled Euler–Lagrange field equations yields a scale factor a(t) (comoving coordinates) that initially exponentially increases N e-folds from a(0) ≈ 0 to a1 = a(0) eN (N = 60 is illustrated), then exponentially decreases, then exponentially increases to a1, and so on almost periodically. (Oscillatory cosmological models are not knew, and have been derived from string theory and loop quantum gravity.) It is not known if the scale factor escapes this periodic trap. This model is noteworthy in several respects: 1. All fundamental fields other than gravity are realized by spinor fields. 2. A plausible connection between the unit field u and the generalization of the photon wave function with a form of Dark Energy is described, and a simple natural scenario is outlined that allocates a fraction of the total energy of the Universe to this form of Dark Energy. 3. A solution of an analog of the pure Einstein–Maxwell equations is found using an approach that is in marked contrast with the method followed to obtain a solution of the well known Friedmann model of a radiation-dominated universe.
Degenerations of Calabi-Yau metrics

This is a survey of our recent work on degenerations of Ricci-flat Kahler metrics on compact Calabi-Yau manifolds with Kahler classes approaching the boundary of the Kahler cone.
Slice implies mutant ribbon for odd 5-stranded pretzel knots

A pretzel knot $K$ is called $odd$ if all its twist parameters are odd, and $mutant$ $ribbon$ if it is mutant to a simple ribbon knot. We prove that the family of odd, 5-stranded pretzel knots satisfies a weaker version of the Slice-Ribbon Conjecture: All slice, odd, 5-stranded pretzel knots are $mutant$ $ribbon$. We do this in stages by first showing that 5-stranded pretzel knots having twist parameters with all the same sign or with exactly one parameter of a different sign have infinite order in the topological knot concordance group, and thus in the smooth knot concordance group as well. Next, we show that any odd, 5-stranded pretzel knot with zero pairs or with exactly one pair of canceling twist parameters is not slice.
Gauging the contribution of X-ray sources to reionization through the kinetic Sunyaev-Zel'dovich effect

Measurements of the kinetic Sunyaev-Zel'dovich (kSZ) effect from instruments such as the South Pole Telescope (SPT) and the Atacama Cosmology Telescope (ACT) will soon put improved constraints on reionization. Popular models assume that UV photons alone are responsible for reionization of the intergalactic medium. We explore the effects of a significant contribution of X-rays to reionization on the kSZ signal. Because X-rays have a large mean free path through the neutral intergalactic medium, they introduce partial ionization in between the sharp-edged bubbles created by UV photons. This smooth ionization component changes the power spectrum of the cosmic microwave background (CMB) temperature anisotropies. We quantify this effect by running semi-numerical simulations of reionization. We test a number of different models of reionization without X-rays that have varying physical parameters, but which are constrained to have similar total optical depths to electron scattering. These are then compared to models with varying levels of contribution to reionization from X-rays. We find that models with more than a 10% contribution from X-rays produce a significantly lower power spectrum of temperature anisotropies than all the UV-only models tested. The expected sensitivity of SPT and ACT may be insufficient to distinguish between our models, however, a non-detection of the kSZ signal from the epoch of reionization could result from the contribution of X-rays. It will be important for future missions with improved sensitivity to consider the impact of X-ray sources on reionization.
Streamlines of the Mean Stellar Motions in Elliptical Galaxies

The stellar velocity fields of elliptical galaxies hold clues to their dynamical structure and origin. The construction of velocity-field models is greatly simplified by assuming an approximate geometrical form for the streamlines of the mean stellar motions, for example, representing the streamlines of short-axis and long-axis tube orbits by coordinate lines in a confocal coordinate system. A single confocal system precisely fits the mean motions of all tube orbits in a Stackel potential, but these potentials are not sufficiently general. Here we test the conjecture that confocal streamlines may still be a valid approximation for more realistic triaxial systems. We numerically integrate orbits in Schwarzschild's logarithmic potential. Six sets of axis ratios are used; in each set, ~50 orbits, comprising short-axis and long-axis tubes as well as some resonant families, are integrated for ~20,000 dynamical times, and the average velocity is found in each of ~4000 spatial cells. Confocal streamlines are compared with the velocity field by finding the rms magnitude of the cross product between the velocity vectors and the streamlines. Minimizing this quantity yields a best-fit confocal system for each orbit. We find that the great majority of orbits at a given energy in each potential can be fitted by nearly identical confocal systems. There are statistically significant differences between the average streamline parameters obtained for different orbit families, but the differences are small. We show that the fitted parameters reproduce, to high accuracy, the location of the boundary between short-axis and outer long-axis tubes, which is a direct measure of the triaxiality of the potential. These results strongly support efforts to obtain accurate statistical measurements of triaxiality from kinematic observations and reasonably simple velocity-field models.
How Does Magnetic Reconnection Drive the Early-stage Evolution of Coronal Mass Ejections?

Theoretically, CME kinematics are related to magnetic reconnection processes in the solar corona. However, the current quantitative understanding of this relationship is based on the analysis of only a handful of events. Here we report a statistical study of 60 CME-flare events from August 2010 to December 2013. We investigate kinematic properties of CMEs and magnetic reconnection in the low corona during the early phase of the eruptions, by combining limb observations from STEREO with simultaneous on-disk views from SDO. For a subset of 42 events with reconnection rate evaluated by the magnetic fluxes swept by the flare ribbons on the solar disk observed from SDO, we find a strong correlation between the peak CME acceleration and the peak reconnection rate. Also, the maximum velocities of relatively fast CMEs (> 600 km/s) are positively correlated with the reconnection flux, but no such correlation is found for slow CMEs. A time-lagged correlation analysis suggests that the distribution of the time lag of CME acceleration relative to reconnection rate exhibits three peaks, approximately 10 minutes apart, and on average, acceleration-lead events have smaller reconnection rates. We further compare the CME total mechanical energy with the estimated energy in the current sheet. The comparison suggests that, for small-flare events, reconnection in the current sheet alone is insufficient to fuel CMEs. Results from this study suggest that flare reconnection may dominate the acceleration of fast CMEs, but for events of slow CMEs and weak reconnection, other mechanisms may be more important.
Minimax value interval for off-policy evaluation and policy optimization

We study minimax methods for off-policy evaluation (OPE) using value functions and marginalized importance weights. Despite that they hold promises of overcoming the exponential variance in traditional importance sampling, several key problems remain: (1) They require function approximation and are generally biased. For the sake of trustworthy OPE, is there anyway to quantify the biases? (2) They are split into two styles ("weight-learning" vs "value-learning"). Can we unify them? In this paper we answer both questions positively. By slightly altering the derivation of previous methods (one from each style; Uehara et al., 2020), we unify them into a single value interval that comes with a special type of double robustness: when either the value-function or the importance-weight class is well specified, the interval is valid and its length quantifies the misspecification of the other class. Our interval also provides a unified view of and new insights to some recent methods, and we further explore the implications of our results on exploration and exploitation in off-policy policy optimization with insufficient data coverage.
Measuring the Delay Time Distribution of Binary Neutron Stars. III. Using the Individual Star Formation Histories of Gravitational-wave Event Host Galaxies in the Local Universe

In Paper I (Safarzadeh & Berger 2019) we studied the determination of the delay time distribution (DTD) of binary neutron stars (BNS) through scaling relations between halo/stellar mass and the star formation history (SFH) of galaxies hosting gravitational wave (GW) events in the local universe. Here we explore how a detailed reconstruction of the individual SFHs of BNS merger host galaxies can improve on the use of the scaling relations. We use galaxies from the Galaxy and Mass Assembly (GAMA) survey, which is mass complete at $M_*>10^9$ M$_\odot$ in the redshift range $0.05<z<0.08$. We use the reconstructed SFHs derived from the Prospector code, for two distinct sets of priors (favoring continuous and bursty SFHs), and convolve those with power law DTDs characterized by an index $\Gamma$ and a minimum delay time $t_{\rm min}$. We find that with this approach $\mathcal{O}(100)-\mathcal{O}(300)$ host galaxies are required to constrain the DTD parameters, with the number depending on the choice of SFH prior and on the parameters of the true DTD. We further show that using only the host galaxies of BNS mergers, as opposed to the full population of potential host galaxies in the relevant cosmic volume, leads to a minor bias in the recovered DTD parameters. The required host galaxy sample size is nearly an order of magnitude smaller relative to the approach of using scaling relations, and we expect such a host galaxy sample to be collected within a decade or two, prior to the advent of third-generation GW detectors.
The shear-free condition and constant-mean-curvature hyperboloidal initial data

We consider the Einstein–Maxwell-fluid constraint equations, and make use of the conformal method to construct and parametrize constant-mean-curvature hyperboloidal initial data sets that satisfy the shear-free condition. This condition is known to be necessary in order that a spacetime development admit a regular conformal boundary at future null infinity; see (Andersson and Chruściel 1994 Commun. Math. Phys. 161 533–68). We work with initial data sets in a variety of regularity classes, primarily considering those data sets whose geometries are weakly asymptotically hyperbolic, as defined in (Allen et al 2015 arXiv:1506.03399). These metrics are C 1,1 conformally compact, but not necessarily C 2 conformally compact. In order to ensure that the data sets we construct are indeed shear-free, we make use of the conformally covariant traceless Hessian introduced in (Allen et al 2015 arXiv:1506.03399). We furthermore construct a class of initial data sets with weakly asymptotically hyerbolic metrics that may be only C 0,1 conformally compact; these data sets are insufficiently regular to make sense of the shear-free condition.
PS16dtm: A Tidal Disruption Event in a Narrow-line Seyfert 1 Galaxy

[Abridged] We present observations of PS16dtm, a luminous transient that occurred at the nucleus of a known Narrow-line Seyfert 1 galaxy hosting a 10$^6$ M$_\odot$ black hole. The transient was previously claimed to be a Type IIn SLSN due to its luminosity and hydrogen emission lines. The light curve shows that PS16dtm brightened by about two magnitudes in ~50 days relative to the archival host brightness and then exhibited a plateau phase for about 100 days followed by the onset of fading in the UV. During the plateau PS16dtm showed no color evolution, maintained a blackbody temperature of 1.7 x 10$^4$ K, and radiated at approximately $L_{Edd}$ of the SMBH. The spectra exhibit multi-component hydrogen emission lines and strong FeII emission, show little evolution with time, and closely resemble the spectra of NLS1s while being distinct from those of Type IIn SNe. Moreover, PS16dtm is undetected in the X-rays to a limit an order of magnitude below an archival X-ray detection of its host galaxy. These observations strongly link PS16dtm to activity associated with the SMBH and are difficult to reconcile with a SN origin or any known form of AGN variability, and therefore we argue that it is a TDE in which the accretion of the stellar debris powers the rise in the continuum and excitation of the pre-existing broad line region, while providing material that obscures the X-ray emitting region of the pre-existing AGN accretion disk. A detailed TDE model fit to the light curve indicates that PS16dtm will remain bright for several years; we further predict that the X-ray emission will reappear on a similar timescale as the accretion rate declines. Finally, we place PS16dtm in the context of other TDEs and find that TDEs in AGN galaxies are an order of magnitude more efficient and reach Eddington luminosities, likely due to interaction of the stellar debris with the pre-existing accretion disk.
A Streaming Approach For Efficient Batched Beam Search

We propose an efficient batching strategy for variable-length decoding on GPU architectures. During decoding, when candidates terminate or are pruned according to heuristics, our streaming approach periodically "refills" the batch before proceeding with a selected subset of candidates. We apply our method to variable-width beam search on a state-of-the-art machine translation model. Our method decreases runtime by up to 71% compared to a fixed-width beam search baseline and 17% compared to a variable-width baseline, while matching baselines' BLEU. Finally, experiments show that our method can speed up decoding in other domains, such as semantic and syntactic parsing.
AXION-ELECTROMAGNETIC WAVES

We extend the duality symmetry between the electric and the magnetic fields to the case in which an additional axion-like term is present, and we derive the set of Maxwell equations that preserves this symmetry. This new set of equations allows for a gauge symmetry extending the ordinary symmetry in the classical electrodynamics. We obtain explicit solutions for the new set of equations in the absence of external sources, and we discuss the implications of a new internal symmetry between the axion field and the electromagnetic gauge potential.
Minimizing metastatic risk in radiotherapy fractionation schedules

Metastasis is the process by which cells from a primary tumor disperse and form new tumors at distant anatomical locations. The treatment and prevention of metastatic cancer remains an extremely challenging problem. This work introduces a novel biologically motivated objective function to the radiation optimization community that takes into account metastatic risk instead of the status of the primary tumor. In this work, we consider the problem of developing fractionated irradiation schedules that minimize production of metastatic cancer cells while keeping normal tissue damage below an acceptable level. A dynamic programming framework is utilized to determine the optimal fractionation scheme. We evaluated our approach on a breast cancer case using the heart and the lung as organs-at-risk (OAR). For small tumor [Formula: see text] values, hypo-fractionated schedules were optimal, which is consistent with standard models. However, for relatively larger [Formula: see text] values, we found the type of schedule depended on various parameters such as the time when metastatic risk was evaluated, the [Formula: see text] values of the OARs, and the normal tissue sparing factors. Interestingly, in contrast to standard models, hypo-fractionated and semi-hypo-fractionated schedules (large initial doses with doses tapering off with time) were suggested even with large tumor α/β values. Numerical results indicate the potential for significant reduction in metastatic risk.
Turbulence Transport Modeling and First Orbit Parker Solar Probe (PSP) Observations

The Parker Solar Probe (PSP) achieved its first orbit perihelion on 2018 November 6, reaching a heliocentric distance of about 0.165 au (35.55 R ⊙). Here, we study the evolution of fully developed turbulence associated with the slow solar wind along the PSP trajectory between 35.55 R ⊙ and 131.64 R ⊙ in the outbound direction, comparing observations to a theoretical turbulence transport model. Several turbulent quantities, such as the fluctuating kinetic energy and the corresponding correlation length, the variance of density fluctuations, and the solar wind proton temperature are determined from the PSP Solar Wind Electrons Alphas and Protons (SWEAP) plasma data along its trajectory between 35.55 R ⊙ and 131.64 R ⊙. The evolution of the PSP derived turbulent quantities are compared to the numerical solutions of the nearly incompressible magnetohydrodynamic (NI MHD) turbulence transport model recently developed by Zank et al. We find reasonable agreement between the theoretical and observed results. On the basis of these comparisons, we derive other theoretical turbulent quantities, such as the energy in forward and backward propagating modes, the total turbulent energy, the normalized residual energy and cross-helicity, the fluctuating magnetic energy, and the correlation lengths corresponding to forward and backward propagating modes, the residual energy, and the fluctuating magnetic energy.
The Importance of System-Level Information in Multiagent Systems Design: Cardinality and Covering Problems

A fundamental challenge in multiagent systems is to design local control algorithms to ensure a desirable collective behavior. The information available to the agents, gathered either through communication or sensing, naturally restricts the achievable performance. Hence, it is fundamental to identify what piece of information is valuable and can be exploited to design control laws with enhanced performance guarantees. This paper studies the case when such information is uncertain or inaccessible for a class of submodular resource allocation problems termed covering problems. In the first part of this paper, we pinpoint a fundamental risk-reward tradeoff faced by the system operator when conditioning the control design on a valuable but uncertain piece of information, which we refer to as the cardinality, that represents the maximum number of agents that can simultaneously select any given resource. Building on this analysis, we propose a distributed algorithm that allows agents to learn the cardinality while adjusting their behavior over time. This algorithm is proved to perform on par or better to the optimal design obtained when the exact cardinality is known a priori .
Towards Electrical-Current Control of Quantum States in Spin-Orbit-Coupled Matter

Novel materials, which often exhibit surprising or even revolutionary physical properties, are necessary for critical advances in technologies. Simultaneous control of structural and physical properties via a small electrical current is of great significance both fundamentally and technologically. Recent studies demonstrate that a combination of strong spin-orbit interactions and a distorted crystal structure in magnetic Mott insulators is sufficient to attain this long-desired goal. In this topical review, we highlight underlying properties of this class of materials and present two representative antiferromagnetic Mott insulators, namely, 4d-electron based Ca2RuO4 and 5d-electron based Sr2IrO4, as model systems. In essence, a small, applied electrical current engages with the lattice, critically reducing structural distortions, which in turn readily suppresses the antiferromagnetic and insulating state and subsequently results in emergent new states. While details may vary in different materials, at the heart of these phenomena are current-reduced lattice distortions, which, via spin-orbit interactions, dictate physical properties. Electrical current, which joins magnetic field, electric field, pressure, light, etc as a new external stimulus, provides a new, key dimension for materials research, and also pose a series of intriguing questions that may provide the impetus for advancing our understanding of spin-orbit-coupled matter. This Topical Review provides a brief introduction, a few hopefully informative examples and some general remarks. It is by no means an exhaustive report of the current state of studies on this topic.
An Analytical Framework for Understanding Tropical Meridional Modes

AbstractA theoretical framework is developed for understanding the transient growth and propagation characteristics of thermodynamically coupled, meridional mode–like structures in the tropics. The model consists of a Gill–Matsuno-type steady atmosphere under the long-wave approximation coupled via a wind–evaporation–sea surface temperature (WES) feedback to a “slab” ocean model. When projected onto meridional basis functions for the atmosphere the system simplifies to a nonnormal set of equations that describes the evolution of individual sea surface temperature (SST) modes, with clean separation between equatorially symmetric and antisymmetric modes. The following major findings result from analysis of the system: 1) a transient growth process exists whereby specific SST modes propagate toward lower-order modes at the expense of the higher-order modes; 2) the same dynamical mechanisms govern the evolution of symmetric and antisymmetric SST modes except for the lowest-order wavenumber, where for symmetri...
ZnS/diamond composite coatings for infrared transmission applications formed by the aerosol deposition method

ABSTRACT The deposition of nano-crystalline ZnS/diamond composite protective coatings on silicon, sapphire, and ZnSsubstrates, as a preliminary step to coating infrared transparent ZnS substrates from powder mixtures by theaerosol deposition method is presented. Advantages of the aerosol deposition method include the ability to formdense, nanocrystalline lms up to hundreds of microns thick at room temperature and at a high deposition rateon a variety of substrates. Deposition is achieved by creating a pressure gradient that accelerates micrometer-scale particles in an aerosol to high velocity. Upon impact with the target substrate the particles fracture andembed. Continued deposition forms the thick compacted lm. Deposition from an aerosolized mixture of ZnS anddiamond powders onto all targets results in linear trend from apparent sputter erosion of the substrate at 100%diamond to formation of a lm with increasing fractions of ZnS. The crossover from abrasion to lm formationon sapphire occurs above about 50% ZnS and a mixture of 90% ZnS and 10% diamond forms a well-adhered lm of about 0.7  m thickness at a rate of 0.14  m/min. Resulting lms are characterized by scanning electronmicroscopy, pro lometry, infrared transmission spectroscopy, and x-ray photoemission spectroscopy. These initial lms mark progress toward the future goal of coating ZnS substrates for abrasion resistance.Keywords: Aerosol Deposition Method, Zinc Sul de, Diamond, Abrasion Resistance, Protective Coating, ThickFilms, Infrared Transmission
Momentum Regularity and Stability of the Relativistic Vlasov-Maxwell-Boltzmann System

In the study of solutions to the relativistic Boltzmann equation, their regularity with respect to the momentum variables has been an outstanding question, even local in time, due to the initially unexpected growth in the post-collisional momentum variables which was discovered in 1991 by Glassey & Strauss (Transport Theory Stat Phys 20(1):55–68, 1991). We establish momentum regularity within energy spaces via a new splitting technique and interplay between the Glassey-Strauss frame and the center of mass frame of the relativistic collision operator. In a periodic box, these new momentum regularity estimates lead to a proof of global existence of classical solutions to the two-species relativistic Vlasov-Maxwell-Boltzmann system for charged particles near Maxwellian with hard ball interaction.
Linearly dependent powers of binary quadratic forms

Given an integer $d \ge 2$, what is the least $r$ so that there is a set of binary quadratic forms $\{f_1,\dots,f_r\}$ for which $\{f_j^d\}$ is non-trivially linearly dependent? We show that if $r \le 4$, then $d \le 5$, and for $d \ge 4$, construct such a set with $r = \lfloor d/2\rfloor + 2$. Many explicit examples are given, along with techniques for producing others.
A general framework for recursive decompositions of unitary quantum evolutions

Decompositions of the unitary group U(n) are useful tools in quantum information theory as they allow one to decompose unitary evolutions into local evolutions and evolutions causing entanglement. Several recursive decompositions have been proposed in the literature to express unitary operators as products of simple operators with properties relevant in entanglement dynamics. In this paper, using the concept of grading of a Lie algebra, we cast these decompositions in a unifying scheme and show how new recursive decompositions can be obtained. In particular, we propose a new recursive decomposition of the unitary operator on N qubits, and give a numerical example.
Lattice gas models with long range interactions

We study microcanonical lattice gas models with long range interactions, including power law interactions. We rigorously obtain a variational principle for the entropy. In a one dimensional example, we find a first order phase transition by proving the entropy is non-differentiable along a certain curve.
Memory-efficient learning of stable linear dynamical systems for prediction and control

Learning a stable Linear Dynamical System (LDS) from data involves creating models that both minimize reconstruction error and enforce stability of the learned representation. We propose a novel algorithm for learning stable LDSs. Using a recent characterization of stable matrices, we present an optimization method that ensures stability at every step and iteratively improves the reconstruction error using gradient directions derived in this paper. When applied to LDSs with inputs, our approach—in contrast to current methods for learning stable LDSs—updates both the state and control matrices, expanding the solution space and allowing for models with lower reconstruction error. We apply our algorithm in simulations and experiments to a variety of problems, including learning dynamic textures from image sequences and controlling a robotic manipulator. Compared to existing approaches, our proposed method achieves an orders-of-magnitude improvement in reconstruction error and superior results in terms of control performance. In addition, it is provably more memory efficient, with an O(n2) space complexity compared to O(n4) of competing alternatives, thus scaling to higher-dimensional systems when the other methods fail. The code of the proposed algorithm and animations of the results can be found at https: //github.com/giorgosmamakoukas/MemoryEfficientStableLDS.
Joint seismic data denoising and interpolation with double-sparsity dictionary learning

Seismic data quality is vital to geophysical applications, so that methods of data recovery, including denoising and interpolation, are common initial steps in the seismic data processing flow. We present a method to perform simultaneous interpolation and denoising, which is based on double-sparsity dictionary learning. This extends previous work that was for denoising only. The original double-sparsity dictionary learning algorithm is modified to track the traces with missing data by defining a masking operator that is integrated into the sparse representation of the dictionary. A weighted low-rank approximation algorithm is adopted to handle the dictionary updating as a sparse recovery optimization problem constrained by the masking operator. Compared to traditional sparse transforms with fixed dictionaries that lack the ability to adapt to complex data structures, the double-sparsity dictionary learning method learns the signal adaptively from selected patches of the corrupted seismic data, while preserving compact forward and inverse transform operators. Numerical experiments on synthetic seismic data indicate that this new method preserves more subtle features in the data set without introducing pseudo-Gibbs artifacts when compared to other directional multi-scale transform methods such as curvelets.
Dynamics of Coronal Hole Boundaries

Remote and in situ observations strongly imply that the slow solar wind consists of plasma from the hot, closed-field corona that is released onto open magnetic field lines. The Separatrix Web theory for the slow wind proposes that photospheric motions at the scale of supergranules are responsible for generating dynamics at coronal-hole boundaries, which result in the closed plasma release. We use three-dimensional magnetohydrodynamic simulations to determine the effect of photospheric flows on the open and closed magnetic flux of a model corona with a dipole magnetic field and an isothermal solar wind. A rotational surface motion is used to approximate photospheric supergranular driving and is applied at the boundary between the coronal hole and helmet streamer. The resulting dynamics consist primarily of prolific and efficient interchange reconnection between open and closed flux. The magnetic flux near the coronal-hole boundary experiences multiple interchange events, with some flux interchanging over 50 times in one day. Additionally, we find that the interchange reconnection occurs all along the coronal-hole boundary and even produces a lasting change in magnetic-field connectivity in regions that were not driven by the applied motions. Our results show that these dynamics should be ubiquitous in the Sun and heliosphere. We discuss the implications of our simulations for understanding the observed properties of the slow solar wind, with particular focus on the global-scale consequences of interchange reconnection.
The Gamma-ray Sky with Fermi

Gamma rays reveal extreme, nonthermal conditions in the Universe. The Fermi Gamma-ray Space Telescope has been exploring the gamma-ray sky for more than four years, enabling a search for powerful transients like gamma-ray bursts, novae, solar flares, and flaring active galactic nuclei, as well as long-term studies including pulsars, binary systems, supernova remnants, and searches for predicted sources of gamma rays such as dark matter annihilation. Some results include a stringent limit on Lorentz invariance derived from a gamma-ray burst, unexpected gamma-ray variability from the Crab Nebula, a huge gamma-ray structure associated with the center of our galaxy, surprising behavior from some gamma-ray binary systems, and a possible constraint on some WIMP models for dark matter.
Carving Out the End of the World or (Superconformal Bootstrap in Six Dimensions)

We bootstrap N=(1,0) superconformal field theories in six dimensions, by analyzing the four-point function of flavor current multiplets. Assuming E_8 flavor group, we present universal bounds on the central charge C_T and the flavor central charge C_J. Based on the numerical data, we conjecture that the rank-one E-string theory saturates the universal lower bound on C_J, and numerically determine the spectrum of long multiplets in the rank-one E-string theory. We comment on the possibility of solving the higher-rank E-string theories by bootstrap and thereby probing M-theory on AdS_7×S^4/ℤ_2.
DECOUPLED AND UNIDIRECTIONAL ASYMPTOTIC MODELS FOR THE PROPAGATION OF INTERNAL WAVES

We study the relevance of various scalar equations, such as inviscid Burgers', Korteweg–de Vries (KdV), extended KdV, and higher order equations, as asymptotic models for the propagation of internal waves in a two-fluid system. These scalar evolution equations may be justified in two ways. The first method consists in approximating the flow by two uncoupled, counterpropagating waves, each one satisfying such an equation. One also recovers these equations when focusing on a given direction of propagation, and seeking unidirectional approximate solutions. This second justification is more restrictive as for the admissible initial data, but yields greater accuracy. Additionally, we present several new coupled asymptotic models: a Green–Naghdi type model, its simplified version in the so-called Camassa–Holm regime, and a weakly decoupled model. All of the models are rigorously justified in the sense of consistency.
Central Limit Theorems for Uniform Model Random Polygons

We show how a central limit theorem for Poisson model random polygons implies a central limit theorem for uniform model random polygons. To prove this implication, it suffices to show that in the two models, the variables in question have asymptotically the same expectation and variance. We use integral geometric expressions for these expectations and variances to reduce the desired estimates to the convergence \((1+\frac{\alpha}{n})^{n}\to e^{\alpha}\) as n→∞.
The homotopy groups of the algebraic K–theory of the sphere spectrum

We calculate π ∗ K ( S ) ⊗ ℤ [ 1 2 ] , the homotopy groups of K ( S ) away from 2 , in terms of the homotopy groups of K ( ℤ ) , the homotopy groups of ℂ P − 1 ∞ and the homotopy groups of S . This builds on work of Waldhausen, who computed the rational homotopy groups (building on work of Quillen and Borel) and Rognes, who calculated the groups at odd regular primes in terms of the homotopy groups of ℂ P − 1 ∞ and the homotopy groups of S .
Plasmon Hybridization in Nanorhombus Assemblies

Understanding resonant coupling in plasmonic nanoassemblies is a challenging scientific endeavor, especially for particles with complex nanoarchitectures. Our ability to both model and measure this...
Ameso optimization: A relaxation of discrete midpoint convexity

Abstract In this paper we introduce the Ameso optimization problem, a special class of discrete optimization problems. We establish its basic properties and investigate the relation between Ameso optimization and the convex optimization. Further, we design an algorithm to solve a multi-dimensional Ameso problem by solving a sequence of one-dimensional Ameso problems. Finally, we demonstrate how the knapsack problem can be solved using the Ameso optimization framework.
Inter-layer per-mobile optimization of cloud mobile computing: a message-passing approach

Cloud mobile computing enables the offloading of computation-intensive applications from a mobile device to a cloud processor via a wireless interface. In light of the strong interplay between offloading decisions at the application-layer and physical-layer parameters, which determine the energy and latency associated with the mobile-cloud communication, this paper investigates the inter-layer optimization of fine-grained task offloading across both layers. In prior art, this problem was formulated, under a serial implementation of processing and communication, as a mixed integer program, entailing a complexity that is exponential in the number of tasks. In this work, instead, algorithmic solutions are proposed that leverage the structure of the call graphs of typical applications by means of message passing on the call graph, under both serial and parallel implementations of processing and communication. For call trees, the proposed solutions have a linear complexity in the number of tasks, and efficient extensions are presented for more general call graphs that include 'map'-type and 'reduce'-type tasks. Moreover, the proposed schemes are optimal for the serial implementation and provide principled heuristics for the parallel implementation. Extensive numerical results yield insights into the impact of inter-layer optimization and on the comparison of the two implementations. Copyright © 2016 John Wiley & Sons, Ltd.
Medical Knowledge-enriched Textual Entailment Framework

One of the cardinal tasks in achieving robust medical question answering systems is textual entailment. The existing approaches make use of an ensemble of pre-trained language models or data augmentation, often to clock higher numbers on the validation metrics. However, two major shortcomings impede higher success in identifying entailment: (1) understanding the focus/intent of the question and (2) ability to utilize the real-world background knowledge to capture the con-text beyond the sentence. In this paper, we present a novel Medical Knowledge-Enriched Textual Entailment framework that allows the model to acquire a semantic and global representation of the input medical text with the help of a relevant domain-specific knowledge graph. We evaluate our framework on the benchmark MEDIQA-RQE dataset and manifest that the use of knowledge-enriched dual-encoding mechanism help in achieving an absolute improvement of 8.27% over SOTA language models.
Learning Theory for Estimation of Animal Motion Submanifolds

This paper describes the formulation and experimental testing of a method to estimate submanifold models of animal motion. It is assumed that the animal motion is supported on a configuration manifold, Q, and that the manifold is homeomorphic to a known smooth, Riemannian manifold, S. Estimation of the configuration submanifold is achieved by approximating an unknown mapping, γ, from S to Q. The overall problem is cast as a distribution-free learning problem over the manifold of measurements. This paper introduces linear approximation spaces in $L_\mu ^2\left(S\right)$ that contain approximations of γ corresponding to those known for classical distribution-free learning theory over Euclidean space. This paper concludes with a study and discussion of the performance of the proposed method using samples from recent reptile motion studies.
Keeping students alive: mandating on-campus counseling saves suicidal college students' lives and limits liability

Suicide among college students is a serious problem in the United States. Conflicting court decisions in the last several years have left colleges wondering whether they may be held liable for a student's suicide. While the law holds that under normal circumstances, colleges do not owe a duty to prevent student suicide, the question becomes murkier once a school begins to treat a student for mental illness. Colleges have encountered additional legal battles because of their voluntary suicide prevention or automatic dismissal policies aimed at students who have either attempted suicide, or expressed a desire to do so. This paper advocates the adoption of a mandatory evaluation program, a model utilized by the University of Illinois at Urbana-Champaign, because it fulfills the threefold goal of keeping students alive, protecting students' privacy rights, and limiting colleges' liability.
Quarter-end repo borrowing dynamics and bank risk opacity

We investigate the extent to which banks’ quarter-end borrowings in the repurchase market deviate from within-quarter levels, and associated factors. Quarter-end repo liabilities are materially lower than within-quarter averages for a large fraction of sample banks. These deviations are more pronounced at banks with a higher concentration of repo borrowings in their liability structure and with larger absolute trading gains or losses. Furthermore, the association with trading activity is mitigated when banks are better capitalized. We also find that these deviations are associated with bank depositor and borrower behavior. Together, the evidence suggests that deviations reflect both active window dressing and passive customer-driven liquidity dynamics. We document that unexpected downward quarter-end deviations in repo liabilities are associated with adverse short-term capital market consequences. Over the long term, banks with more frequent downward quarter-end deviations exhibit higher credit risk, but we find mixed evidence for equity market valuation multiples.
Inner-city anti-poverty campaigns

This Article offers a defense of outsider, legal-political intervention and community triage in inner-city anti-poverty campaigns under circumstances of widespread urban social disorganization, public and private sector neglect, and nonprofit resource scarcity. In mounting this defense, the Article revisits the roles of lawyers, nonprofit legal services organizations, and university-housed law school clinics in contemporary anti-poverty, civil rights, and social justice movements, in part by chronicling the emergence of a faith-based municipal equity movement in Miami, Florida. The Article proceeds in four parts. Part I introduces the notion of community triage as a means of addressing the impoverished and segregated aftermath of urban development in a cluster of postindustrial inner cities. Part II examines the First Wave of antipoverty campaigns launched by pioneering legal services and public interest lawyers and their evolving community triage models. Part III surveys the Second Wave of anti-poverty campaigns pressed by more client- and community-centered legal services and public interest lawyers and their alternative community triage paradigms. Part IV appraises the Third Wave of anti-poverty campaigns kindled by a new generation of legal services and public interest lawyers and their site-specific community triage approaches in the fields of community economic development, environmental justice, low-wage labor, immigration, and municipal equity in order to discern legal-political lessons of inner-city advocacy and organizing. Taken together, the four parts forge a larger legal-political vision imagined and reimagined daily by a new generation of social movement activists and scholars — a renewed vision of theory-driven, clinical practice tied to empirical research and experiential reflection about law and lawyers in action.
A trail guide to publishing success: Tips on writing influential conceptual, qualitative, and survey research

Publishing in top journals is difficult. Common challenges undermine authors' attempts to explain and influence their discipline's understanding and practice. We identify and describe these roadblocks to publishing success. We also benchmark best practice in management, marketing, and supply chain journals to provide a trail guide for writing—and publishing—influential conceptual, qualitative, and survey research. Given equifinality in research, our trail guide should not be viewed as the only way to craft excellent, influential research. However, if we agree on the basics, we can (1) increase consistency in the review process, (2) reduce publication cycles, and (3) begin to roll back the length of articles.
Lawyers and Precedent

What role do lawyers, as lawyers, play in the creation, development, and maintenance of the international legal order? This is an oddly underexplored question. It has become increasingly popular to look at the role various non-state actors—nongovernmental organizations (NGOs), 1 grassroots activists, 2 scientists, 3 insurgent groups, 4 among many others—play in the shaping of international law. It has also
Assessing the Energy-Efficiency Gap

Energy-efficient technologies offer considerable promise for reducing the financial costs and environmental damages associated with energy use, but it has long been observed that these technologies may not be adopted by individuals and firms to the degree that might be justified, even on a purely financial basis. We survey the relevant literature on this "energy-efficiency gap" by presenting two complementary frameworks. First, we divide potential explanations for the energy-efficiency gap into three categories: market failures, behavioral explanations, and model and measurement errors. Second, we organize previous research in terms of the fundamental elements of cost-minimizing energy-efficiency decisions. This provides a decomposition that organizes thinking around four questions. First, are product offerings and pricing economically efficient? Second, are energy operating costs inefficiently priced and/or understood? Third, are product choices cost minimizing in present value terms? Fourth, do other costs inhibit more energy-efficient decisions? We synthesize academic research on these questions, with an emphasis on recent empirical findings, and offer suggestions for future research.
Subtle Signals of Inconspicuous Consumption

While theories of signaling and conspicuous consumption suggest that more explicit markers facilitate communication, this article examines the utility of subtle signals. Four studies demonstrate that while less explicit branding increases the likelihood of misidentification (e.g., observers confusing a high-end purchase for a cheaper alternative), people with more cultural capital in a particular domain prefer subtle signals because they provide differentiation from the mainstream. Such insiders have the necessary connoisseurship to decode the meaning of subtle signals that facilitate communication with others “in the know.” Consistent with the notion that these effects are driven by outward communication, they are stronger in identity-relevant product domains and situations where consumption is more public. This work highlights the communication value of less explicit signals and discusses the implications for branding, signal persistence, and the communication of identity.
Safeguarding Federalism by Saving Health Reform: Implications of National Federation of Independent Business v. Sebelius

On June 28, 2012, the Supreme Court issued one of its most anticipated decisions in National Federation of Independent Business v. Sebelius (“NFIB”) - the constitutional challenge to the Patient Protection and Affordable Care Act (“ACA”). Two main goals of the ACA - increasing private insurance coverage and the Medicaid expansion - have been the targets of a number of legal challenges that reached the Supreme Court in NFIB. The first, and the one that has received the most attention, was the challenge to the individual mandate as exceeding Congress’s commerce and taxing powers. The second was a challenge to the structure of the Medicaid expansion as coercive in violation of the Tenth Amendment limit on Congress’s spending power. Reform opponents claimed that upholding the mandate would lead to an unprecedented expansion of federal power. They shaped the dominant narrative that presented federal power as an inherent threat to state sovereignty and individual liberty. In this narrative, NFIB presented the Court with a dichotomous choice: Would the conservative majority - Chief Justice Roberts, along with Justices Alito, Scalia, Thomas, and Kennedy - take this opportunity to further limit federal power, or could the liberal wing of the court sway one of the other Justices (most wrongly predicted Justice Kennedy) to uphold the mandate? The Court surprised many by answering “yes” to both.The Court upheld the mandate as a constitutional exercise of the taxing power and preserved the Medicaid expansion as an option for states, but Chief Justice Roberts’s approach defied the simplistic narrative that dominated commentary before the decision. By upholding the mandate and the ACA, the Court has preserved a powerful new version of cooperative federalism in healthcare - one that creates a federal platform for state experimentation, innovation, and regulation to facilitate meaningful choice in the private health-insurance market. At the same time, however, Chief Justice Roberts penned certain parts of the opinion that may advance more traditional federalist aims of limiting the commerce and spending powers.