cssi/SciSciGPT-SciSciNet huggingface dataset:
Magnetic Vortex Crystals in Frustrated Mott Insulator

Large-scale ordering of nonelementary mesoscopic magnetic structures is both fundamentally fascinating and technologically relevant. A theoretical study of frustrated quantum magnets predicts the emergence of a new class of stable magnetic vortex crystals under general conditions.
On the Lagrangian Structure of the Discrete Isospectral and Isomonodromic Transformations

We study the Lagrangian properties of the discrete isospectral and isomonodromic dynamical systems. We generalize the Moser-Veselov approach to integrability of discrete isospectral systems via the refactorization of matrix polynomials to matrix rational functions with a simple divisor, and consider in detail the case of two poles or, equivalently, of two elementary factors. In this case, we establish, by explicitly writing down the Lagrangian, that the isomonodromic dynamic is Lagrangian. Next, we show how to make this Lagrangian time dependent to obtain the equations of the isomonodromic dynamic. In some special cases, such equations are known to reduce to the difference Painleve equations. We show how to obtain the difference Painleve V equation in that way, establishing that dPV can be written in the Lagrangian form.
ADDITIONAL MASSIVE BINARIES IN THE CYGNUS OB2 ASSOCIATION

We report the discovery and orbital solutions for two new OB binaries in the Cygnus OB2 Association, MT311 (B2V + B3V) and MT605 (B0.5V + B2.5:V). We also identify the system MT429 as a probable triple system consisting of a tight eclipsing 2.97 day B3V+B6V pair and a B0V at a projected separation of 138 AU. We further provide the first spectroscopic orbital solutions to the eclipsing, double-lined, O-star binary MT696 (O9.5V + B1:V), the double-lined, early B binary MT720 (B0-1V + B1-2V), and the double-lined, O-star binary MT771 (O7V + O9V). These systems exhibit orbital periods between 1.5 days and 12.3 days, with the majority having P <6 days. The two new binary discoveries and six spectroscopic solutions bring the total number of known massive binaries in the central region of the Cygnus OB2 Association to 20, with all but two having full orbital solutions.
A Hubble Space Telescope Study of Lyman Limit Systems: Census and Evolution

We present a survey for optically thick Lyman limit absorbers at z 19.0, there is some evidence that f(N H I ) evolves with z for log N H I 17.7, possibly due to the evolution of the UV background and galactic feedback. Assuming LLSs are associated with individual galaxies, we show that the physical cross section of the optically thick envelopes of galaxies decreased by a factor of ~9 from z ~ 5 to 2 and has remained relatively constant since that time. We argue that a significant fraction of the observed population of LLSs arises in the circumgalactic gas of sub-L * galaxies.
THE OPTICAL ORBITAL LIGHT CURVE OF THE LOW-MASS X-RAY BINARY V1408 AQUILAE (= 4U 1957+115)

V1408 Aql (= 4U 1957+115) is a low-mass X-ray binary with an orbital period of nearly 9.3 hr, whose compact star is a black hole candidate. The system shows a large-amplitude orbital photometric modulation at optical wavelengths. We have obtained new optical photometry of V1408 Aql from which we derive the orbital light curve and an improved orbital ephemeris. We show that the orbital light curve can be reproduced by a model in which the accretion disk around the compact star is thin, axisymmetric, and uneclipsed. The secondary star is heated by X-rays from the compact star and the accretion disk. The orbital modulation is produced entirely by the changing aspect of the irradiated secondary star with orbital phase. Because the system does not eclipse, the fits of the model light curves are insensitive to the orbital parameters, allowing a wide range of orbital inclinations and mass ratios.
Probing the metal-insulator transition of NdNiO3 by electrostatic doping

Modulation of the charge carrier density in a Mott material by remote doping from a highly doped conventional band insulator is proposed to test theoretical predictions of band filling control of the Mott metal-insulator transition without introducing lattice distortions or disorder, as is the case for chemical doping. The approach is experimentally tested using ultrathin (2.5 nm) NdNiO3 films that are epitaxially grown on La-doped SrTiO3 films. We show that remote doping systematically changes the charge carrier density in the NdNiO3 film and causes a moderate shift in the metal-insulator transition temperature. These results are discussed in the context of theoretical models of this class of materials exhibiting a metal-insulator transition.
PCNNA: A Photonic Convolutional Neural Network Accelerator

Convolutional Neural Networks (CNN) have been the centerpiece of many applications including but not limited to computer vision, speech processing, and Natural Language Processing (NLP). However, the computationally expensive convolution operations impose many challenges to the performance and scalability of CNNs. In parallel, photonic systems, which are traditionally employed for data communication, have enjoyed recent popularity for data processing due to their high bandwidth, low power consumption, and reconfigurability. Here we propose a Photonic Convolutional Neural Network Accelerator (PCNNA) as a proof of concept design to speedup the convolution operation for CNNs. Our design is based on the recently introduced silicon photonic microring weight banks, which use broadcast-and-weight protocol to perform Multiply And Accumulate (MAC) operation and move data through layers of a neural network. Here, we aim to exploit the synergy between the inherent parallelism of photonics in the form of Wavelength Division MUltiplexing (WDM) and sparsity of connections between input feature maps and kernels in CNNs. While our full system design offers up to more than 3 orders of magnitude speedup in execution time, its optical core potentially offer more than 5 order of magnitude speedup compared to state-of-the-art electronic counterparts.
Distributed Inertial Best-Response Dynamics

The note considers the problem of computing pure Nash equilibrium (NE) strategies in distributed (i.e., network-based) settings. The paper studies a class of inertial best-response dynamics based on the fictitious play (FP) algorithm. It is shown that inertial best-response dynamics are robust to informational limitations common in distributed settings. Fully distributed variants of FP with inertia and joint strategy FP (JSFP) with inertia are developed and convergence is proven to the set of pure NE. The distributed algorithms developed in the paper rely on consensus methods. Results are validated using numerical simulations.
Quadratic corrections to the metaplectic formulation of resonant mode conversion

The effects of quadratic order terms in the dispersion matrix near a mode conversion are considered. It is shown that including the corrections due to these quadratic terms gives a better matching between the local solution in the mode conversion region, and the far-field WKB solutions for the incoming and outgoing waves. This matching is demonstrated by comparison of the asymptotic solution with a numerical solution for a simple one-dimensional conversion. This procedure for obtaining the corrections due to quadratic order terms can be extended to arbitrary order and, in principle, an outline for performing such an extension is given.
Effects of tip-nanotube interactions on atomic force microscopy imaging of carbon nanotubes

We examine the effect of van der Waals (vdW) interactions between atomic force microscope tips and individual carbon nanotubes (CNTs) supported on SiO2. Molecular dynamics (MD) simulations reveal how CNTs deform during atomic force microscopy (AFM) measurement, irrespective of the AFM tip material. The apparent height of a single- (double-) walled CNT can be used to estimate its diameter up to ∼2 nm (∼3 nm), but for larger diameters the CNT cross-section is no longer circular. Our simulations were compared against CNT dimensions obtained from AFM measurements and resonant Raman spectroscopy, with good agreement for the smaller CNT diameters. In general, AFM measurements of large-diameter CNTs must be interpreted with care, but the reliability of the approach is improved if knowledge of the number of CNT walls is available, or if additional verification (e.g., by optical techniques) can be obtained. Open image in new window
SMALL-SCALE PROPERTIES OF ATOMIC GAS IN EXTENDED DISKS OF GALAXIES

We present high-resolution H I 21 cm observations with the Karl G. Jansky Very Large Array for three H I rich galaxies in absorption against radio quasars. Our sample contains six sightlines with impact parameters from 2.6 to 32.4 kpc. We detected a narrow H I absorber of FWHM 1.1 km s?1 at 444.5 km s?1 toward SDSS?J122106.854+454852.16 probing the dwarf galaxy UCG 7408 at an impact parameter of 2.8 kpc. The absorption feature was barely resolved and its width corresponds to a maximum kinetic temperature, Tk 26 K. We estimate a limiting peak optical depth of 1.37 and a column density of 6 ? 1019 cm?2. The physical extent of the absorber is 0.04 kpc2 and covers ~25%-30% of the background source. A comparison between the emission and absorption strengths suggests the cold-to-total H I column density in the absorber is ~30%. Folding in the covering fraction, the cold-to-total H I mass is ~10%. This suggest that condensation of warm H I (Ts ~ 1000 K) to cold phase (Ts 1000 K) toward these sightlines.
AutoBlock: A Hands-off Blocking Framework for Entity Matching

Entity matching seeks to identify data records over one or multiple data sources that refer to the same real-world entity. Virtually every entity matching task on large datasets requires blocking, a step that reduces the number of record pairs to be matched. However, most of the traditional blocking methods are learning-free and key-based, and their successes are largely built on laborious human effort in cleaning data and designing blocking keys. In this paper, we propose AutoBlock, a novel hands-off blocking framework for entity matching, based on similarity-preserving representation learning and nearest neighbor search. Our contributions include: (a) Automation: AutoBlock frees users from laborious data cleaning and blocking key tuning. (b) Scalability: AutoBlock has a sub-quadratic total time complexity and can be easily deployed for millions of records. (c) Effectiveness: AutoBlock outperforms a wide range of competitive baselines on multiple large-scale, real-world datasets, especially when datasets are dirty and/or unstructured.
Tunable Acoustic Valley-Hall Edge States in Reconfigurable Phononic Elastic Waveguides

Controlling the flow of mechanical energy in elastic structures has been a long-standing challenge in many areas of engineering, particularly those dealing with vibrations and structure-borne noise. In light of recent studies on the quantum valley Hall effect in electronic systems, the authors show that $a\phantom{\rule{0}{0ex}}c\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}u\phantom{\rule{0}{0ex}}s\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}c$ topological edge states can be achieved, at a boundary or interface between two elastic waveguides having broken space-inversion symmetry. The topological properties of such waveguides can be tuned by applying a controlled strain field, while the resulting edge states show a relatively high insensitivity to defects.
Enhanced Cosmic-Ray Flux and Ionization for Star Formation in Molecular Clouds Interacting with Supernova Remnants

Molecular clouds interacting with supernova remnants may be subject to greatly enhanced irradiation by cosmic rays produced at the shocked interface between the ejecta and the molecular gas. Over the past decade, broadband observations have provided important clues about these relativistic particles, indicating that they may dominate over the locally observed cosmic-ray population by a significant amount. In this Letter, we estimate the enhancement and find that the cosmic-ray energy density can be up to ~1000 times larger in the molecular cloud than in the field. This enhancement can last for a few million years and leads to a corresponding increase in the ionization fraction, which has important consequences for star formation. Ionization fractions in molecular cloud cores determine, in part, the rate of ambipolar diffusion, an important process in core formation and precollapse evolution. Ionization fractions in newly formed circumstellar disks affect the magnetorotational instability mechanism, which in turn affects the rate of disk accretion. As estimated here, the increased ionization acts to increase the ambipolar diffusion time by a factor of ~30 and thereby suppresses star formation. In contrast, the increased ionization fraction reduces the sizes of dead zones in accretion disks (by up to an order of magnitude) and thus increases disk accretion rates (by a comparable factor).
Bistability in the rotational motion of rigid and flexible flyers

We explore the rotational stability of hovering flight in an idealized two-dimensional model. Our model is motivated by an experimental pyramid-shaped object (Weathers et al., J. Fluid Mech, vol. 650, 2010, pp. 415–425; Liu et al., Phys. Rev. Lett., vol. 108, 2012, 068103) and a computational -shaped analogue (Huang et al., Phys. Fluids, vol. 27 (6), 2015, 061706; Huang et al., J. Fluid Mech., vol. 804, 2016, pp. 531–549) hovering passively in oscillating airflows; both systems have been shown to maintain rotational balance during free flight. Here, we attach the -shaped flyer at its apex in oscillating flow, allowing it to rotate freely akin to a pendulum. We use computational vortex sheet methods and we develop a quasi-steady point-force model to analyse the rotational dynamics of the flyer. We find that the flyer exhibits stable concave-down ( ) and concave-up ( ) behaviour. Importantly, the down and up configurations are bistable and co-exist for a range of background flow properties. We explain the aerodynamic origin of this bistability and compare it to the inertia-induced stability of an inverted pendulum oscillating at its base. We then allow the flyer to flap passively by introducing a rotational spring at its apex. For stiff springs, flexibility diminishes upward stability but as stiffness decreases, a new transition to upward stability is induced by flapping. We conclude by commenting on the implications of these findings for biological and man-made aircraft.
DYNAMICAL CORRELATION THEORY FOR AN ESCAPE PROCESS

A dynamical theory which incorporates the electron-electron correlations and the effects of external magnetic fields for an electron escaping from a helium surface are presented. The degrees of freedom in the calculation of the escape rate is reduced from 3N to 3 as compared with other approach. Explicit expressions for the escape rate in various situations are obtained. In particular, in the weak parallel magnetic field limit, the tunneling rate has an exponential dependence quadratic with magnetic field strength and an unusual exponential increase linear with temperature.
A Note on Matter Covariantization for Gravity Coupling

Covariantization is of course required for initially flat space matter actions to couple consistently to GR; here we show in detail for concrete systems how it follows in the same physical way as that deriving GR from its initial free field form.
Weyl nodes in periodic structures of superconductors and spin-active materials.

Motivated by recent progress in epitaxial growth of proximity structures of s -wave superconductors (S) and spin-active materials (M), in this paper we show that certain periodic structures of S and M can behave effectively as superconductors with pairs of point nodes, near which the low-energy excitations are Weyl fermions. A simple model, where M is described by a Kronig–Penney potential with both spin–orbit coupling and exchange field, is proposed and solved to obtain the phase diagram of the nodal structure, the spin texture of the Weyl fermions, as well as the zero-energy surface states in the form of open Fermi lines (Fermi arcs). As a second example, a lattice model with alternating layers of S and magnetic Z 2 topological insulators is solved. The calculated spectrum confirms previous predictions of Weyl nodes based on the tunnelling Hamiltonian of Dirac electrons. Our results provide further evidence that periodic structures of S and M are well suited for engineering gapless topological superconductors. This article is part of the theme issue ‘Andreev bound states’.
Optical Counterparts to Galaxies in the Cen A Group Discovered by HIPASS

We have completed a 21-cm survey of a 600 square degree region of the Centaurus A group of galaxies at a redshift of ~500 km s-1 as part of a larger survey of the entire southern sky. This group of galaxies was recently the subject of a separate and thorough optical survey (Cote et al. 1997), and thus presented an ideal comparison for us to test the survey performance. We have identified 10 new group members to add to the 21 already known in our survey area. Six of the new members are previously uncatalogued galaxies, while four were catalogued but assumed not to be group members. Including the seven known members outside of our survey area, this brings the total known number of Cen A members to 38. All of the new HI detections have optical counterparts, most being intrinsically very faint (M_B > -13.0), late-type low surface brightness dwarfs. Most of the new members have HI masses only a few times our survey limit of 10^7 M_sun at an assumed distance for the group of 3.5 Mpc, and are extremely gas-rich, with a median M_HI / L_B > 1. Our limiting HI sensitivity was actually slightly worse than the HI follow-up observations of the Cote et al. optical survey, yet we have already increased the known number of group members by 50% using an HI survey technique. While we have increased the known number of members by ~50%, these new members contribute < 4% to its light.
Privacy via the Johnson-Lindenstrauss Transform

Suppose that party A collects private information about its users, where each user's data is represented as a bit vector. Suppose that party B has a proprietary data mining algorithm that requires estimating the distance between users, such as clustering or nearest neighbors. We ask if it is possible for party A to publish some information about each user so that B can estimate the distance between users without being able to infer any private bit of a user. Our method involves projecting each user's representation into a random, lower-dimensional space via a sparse Johnson-Lindenstrauss transform and then adding Gaussian noise to each entry of the lower-dimensional representation. We show that the method preserves differential privacy---where the more privacy is desired, the larger the variance of the Gaussian noise. Further, we show how to approximate the true distances between users via only the lower-dimensional, perturbed data. Finally, we consider other perturbation methods such as randomized response and draw comparisons to sketch-based methods. While the goal of releasing user-specific data to third parties is more broad than preserving distances, this work shows that distance computations with privacy is an achievable goal.
TriNE: Network Representation Learning for Tripartite Heterogeneous Networks

In this paper, we study network representation learning for tripartite heterogeneous networks which learns node representation features for networks with three types of node entities. We argue that tripartite networks are common in real-world applications, and the essential challenge of the representation learning is the heterogeneous relations between various node types and links in the network. To tackle the challenge, we develop a tripartite heterogeneous network embedding called TriNE. The method considers unique user-item-tag tripartite relationships, to build an objective function to model explicit relationships between nodes (observed links), and also capture implicit relationships between tripartite nodes (unobserved links across tripartite node sets). The method organizes metapath-guided random walks to create heterogeneous neighborhood for all node types in the network. This information is then utilized to train a heterogeneous skip-gram model based on a joint optimization. Experiments on real-world tripartite networks validate the performance of TriNE for the online user response prediction using embedding node features.
The Efficiency of Noble Gas Trapping in Astrophysical Environments

Amorphous ice has long been invoked as a means for trapping extreme volatiles into solids, explaining the abundances of these species in comets and planetary atmospheres. Experiments have shown that this trapping is possible and has been used to estimate the abundances of each species in primitive ices after they have formed. However, these experiments have been carried out at deposition rates that exceed those expected in a molecular cloud or solar nebula by many orders of magnitude. Here, we develop a numerical model that reproduces the experimental results and apply it to those conditions expected in molecular clouds and protoplanetary disks. We find that two regimes of ice trapping exist: burial trapping, where the ratio of trapped species to water in the ice reflects that same ratio in the gas; and equilibrium trapping, where the ratio in the ice depends only on the partial pressure of the trapped species in the gas. The boundary between these two regimes is set by both the temperature and rate of ice deposition. These effects must be accounted for when determining the source of trapped volatiles during planet formation.
i-flow: High-dimensional Integration and Sampling with Normalizing Flows

In many fields of science, high-dimensional integration is required. Numerical methods have been developed to evaluate these complex integrals. We introduce the code i-flow, a python package that performs high-dimensional numerical integration utilizing normalizing flows. Normalizing flows are machine-learned, bijective mappings between two distributions. i-flow can also be used to sample random points according to complicated distributions in high dimensions. We compare i-flow to other algorithms for high-dimensional numerical integration and show that i-flow outperforms them for high dimensional correlated integrals. The i-flow code is publicly available on gitlab at this https URL.
Lepton Acceleration in Pulsar Wind Nebulae

Pulsar Wind Nebulae (PWNe) act as calorimeters for the relativistic pair winds emanating from within the pulsar light cylinder. Their radiative dissipation in various wavebands is significantly different from that of their pulsar central engines: the broadband spectra of PWNe possess characteristics distinct from those of pulsars, thereby demanding a site of lepton acceleration remote from the pulsar magnetosphere. A principal candidate for this locale is the pulsar wind termination shock, a putatively highly-oblique, ultra-relativistic MHD discontinuity. This paper summarizes key characteristics of relativistic shock acceleration germane to PWNe, using predominantly Monte Carlo simulation techniques that compare well with semi-analytic solutions of the diffusion-convection equation. The array of potential spectral indices for the pair distribution function is explored, defining how these depend critically on the parameters of the turbulent plasma in the shock environs. Injection efficiencies into the acceleration process are also addressed. Informative constraints on the frequency of particle scattering and the level of field turbulence are identified using the multiwavelength observations of selected PWNe. These suggest that the termination shock can be comfortably invoked as a principal injector of energetic leptons into PWNe without resorting to unrealistic properties for the shock layer turbulence or MHD structure.
Relativistic quantum theories and neutrino oscillations

Neutrino oscillations are examined under the broad requirements of Poincare-invariant scattering theory in an S-matrix formulation. This approach can be consistently applied to theories with either field or particle degrees of freedom. The aim of this paper is to use this general framework to identify all of the unique physical properties of this problem that lead to a simple oscillation formula. We discuss what is in principle observable and how many factors that are important in principle end up being negligible in practice.
Measuring the distance between quantum many-body wave functions

We study the distance of two wave functions under chaotic time evolution. The two initial states differ only by a local perturbation. To be entitled 'chaos' the distance should have a rapid growth afterwards. Instead of focusing on the entire wave function, we measure the distance d 2(t) by investigating the difference of two reduced density matrices of the subsystem A that is spatially separated from the local perturbation. This distance d 2(t) grows with time and eventually saturates to a small constant. We interpret the distance growth in terms of operator scrambling picture, which relates d 2(t) to the square of commutator (out-of-time-order correlator) and shows that both these quantities measure the area of the operator wave front in subsystem A. Among various one-dimensional spin- models, we numerically show that the models with non-local power-law interaction can have an exponentially growing regime in d 2(t) when the local perturbation and subsystem A are well separated. This so-called Lyapunov regime is absent in the spin- chain with local interaction only. After sufficiently long time evolution, d 2(t) relaxes to a small constant, which decays exponentially as we increase the system size and is consistent with eigenstate thermalization hypothesis. Based on these results, we demonstrate that d 2(t) is a useful quantity to characterize both quantum chaos and quantum thermalization in many-body wave functions.
Decompositions of cellular binomial ideals

Without any restrictions on the base field, we compute the hull and prove a conjecture of Eisenbud and Sturmfels, giving an unmixed decomposition of a cellular binomial ideal. Over an algebraically closed field, we further obtain an explicit (but not necessarily minimal) primary decomposition of such an ideal.
Semiclassical correlators in Jackiw-Teitelboim gravity

In the semiclassical approximation to JT gravity, we find two-point and four- point correlators of heavy operators. To do so, we introduce a massive particle in the bulk and compute its action with gravitational backreaction. In Euclidean signature, the two- point function has a finite limit at large distances. In real time, we find that the thermal two-point function approaches an exponentially small value ∼ exp(−N) at long time. We also find that after a period of exponential decay, the out of time ordered four-point function approaches an exponentially small value as well.
Floer homology of families I

Floer theory is a certain kind of generalization of Morse theory, of which there are now a number of different flavors. These give invariants of symplectomorphisms, 3‐manifolds, Legendrian knots, and many other types of objects. This paper describes a fundamental structure which apparently exists in most or all versions of Floer theory. The structure in question is a homotopy invariant of families of equivalent objects parametrized by a smooth manifold B . Its different manifestations thus give invariants of families of Hamiltonian isotopic symplectomorphisms, families of 3‐manifolds, etc. The invariant of a family consists of a filtered chain homotopy type, which gives rise to a spectral sequence whose E 2 term is the homology of B with local coefficients in the Floer homology of the fibers. This filtered chain homotopy type also gives rise to a “family Floer homology” to which the spectral sequence converges. The general properties of this family invariant are stated in the “Main Principle” below. This principle cannot be formulated as a general theorem, because there is no precise definition of “Floer theory” that encompasses all of its diverse variants. For any particular version of Floer theory, in order to turn the principle into a theorem, one needs to slightly extend the construction of the Floer theory in question and check that the requisite analysis goes through. The rest of this paper constructs the invariant in detail for the model version of Floer theory, namely finite-dimensional Morse homology,
A doubly localized equilibrium solution of plane Couette flow

We present an equilibrium solution of plane Couette flow that is exponentially localized in both the spanwise and streamwise directions. The solution is similar in size and structure to previously computed turbulent spots and localized, chaotically wandering edge states of plane Couette flow. A linear analysis of dominant terms in the Navier–Stokes equations shows how the exponential decay rate and the wall-normal overhang profile of the streamwise tails are governed by the Reynolds number and the dominant spanwise wavenumber. Perturbations of the solution along its leading eigenfunctions cause rapid disruption of the interior roll-streak structure and formation of a turbulent spot, whose growth or decay depends on the Reynolds number and the choice of perturbation.
Local, non-geodesic, timelike currents in the force-free magnetosphere of a Kerr black hole

In this paper, we use previously developed exact solutions to present some of the curious features of a force-free magnetosphere in a Kerr background. More precisely, we obtain a hitherto unseen timelike current in the force-free magnetosphere that does not flow along a geodesic. The electromagnetic field in this case happens to be magnetically dominated. Changing the sign of a single parameter in our solutions generates a spacelike current that creates an electromagnetic field that is electrically dominated.
Spatial Data Infrastructures

Spatial data infrastructure (SDI) is the infrastructure that facilitates the discovery, access, management, distribution, reuse, and preservation of digital geospatial resources. These resources may include maps, data, geospatial services, and tools. As cyberinfrastructures, SDIs are similar to other infrastructures, such as water supplies and transportation networks, since they play fundamental roles in many aspects of the society. These roles have become even more significant in today's big data age, when a large volume of geospatial data and Web services are available. From a technological perspective, SDIs mainly consist of data, hardware, and software. However, a truly functional SDI also needs the efforts of people, supports from organizations, government policies, data and software standards, and many others. In this chapter, we will present the concepts and values of SDIs, as well as a brief history of SDI development in the U.S. We will also discuss the components of a typical SDI, and will specifically focus on three key components: geoportals, metadata, and search functions. Examples of the existing SDI implementations will also be discussed.
Jump locations of jump-diffusion processes with state-dependent rates

We propose a general framework for studying statistics of jump-diffusion systems driven by both Brownian noise (diffusion) and a jump process with state-dependent intensity. Of particular natural interest in many physical systems are the jump locations: the system evaluated at the jump times. As an example, this could be the voltage at which a neuron fires, or the so-called 'threshold voltage'. However, the state-dependence of the jump rate provides direct coupling between the diffusion and jump components, making it difficult to disentangle the two to study individually. In this work, we provide an iterative map formulation of the sequence of distributions of jump locations. The distributions computed by this map can be used to elucidate other interesting quantities about the process, including statistics of the interjump times. Ultimately, the limit of the map reveals that knowledge of the stationary distribution of the full process is sufficient to recover (but not necessarily equal to) the distribution of jump locations. We propose two biophysical examples to illustrate the use of this framework to provide insight about a system. We find that a sharp threshold voltage emerges robustly in a simple stochastic integrate-and-fire neuronal model. The interplay between the two sources of noise is also investigated in a stepping model of molecular motor in intracellular transport pulling a diffusive cargo.
Time Domain Filtering of Resolved Images of Sgr A

The goal of the Event Horizon Telescope (EHT) is to provide spatially resolved images of Sgr A*, the source associated with the Galactic Center black hole. Because Sgr A* varies on timescales short compared to an EHT observing campaign, it is interesting to ask whether variability contains information about the structure and dynamics of the accretion flow. In this paper, we introduce "time-domain filtering", a technique to filter time fluctuating images with specific temporal frequency ranges, and demonstrate the power and usage of the technique by applying it to mock millimeter wavelength images of Sgr A*. The mock image data is generated from General Relativistic Magnetohydrodynamic (GRMHD) simulation and general relativistic ray-tracing method. We show that the variability on each line of sight is tightly correlated with a typical radius of emission. This is because disk emissivity fluctuates on a timescale of order the local orbital period. Time-domain filtered images therefore reflect the model dependent emission radius distribution, which is not accessible in time-averaged images. We show that, in principle, filtered data have the power to distinguish between models with different black hole spins, different disk viewing angles, and different disk orientations in the sky.
A Numerical Study on the Weak Galerkin Method for the Helmholtz Equation

A weak Galerkin (WG) method is introduced and numerically tested for the Helmholtz equation. This method is flexible by using discontinuous piecewise polynomials and retains the mass conservation property. At the same time, the WG finite element formulation is symmetric and parameter free. Several test scenarios are designed for a numerical investigation on the accuracy, convergence, and robustness of the WG method in both inhomogeneous and homogeneous media over convex and non-convex domains. Challenging problems with high wave numbers are also examined. Our numerical experiments indicate that the weak Galerkin is a finite element technique that is easy to implement, and provides very accurate and robust numerical solutions for the Helmholtz problem with high wave numbers.
A robust modeling framework for energy analysis of data centers

Global digitalization has given birth to the explosion of digital services in approximately every sector of contemporary life. Applications of artificial intelligence, blockchain technologies, and internet of things are promising to accelerate digitalization further. As a consequence, the number of data centers, which provide the services of data processing, storage, and communication services, is also increasing rapidly. Because data centers are energy-intensive with significant and growing electricity demand, an energy model of data centers with temporal, spatial, and predictive analysis capability is critical for guiding industry and governmental authorities for making technology investment decisions. However, current models fail to provide consistent and high dimensional energy analysis for data centers due to severe data gaps. This can be further attributed to the lack of the modeling capabilities for energy analysis of data center components including IT equipment and data center cooling and power provisioning infrastructure in current energy models. In this research, a technology-based modeling framework, in hybrid with a data-driven approach, is proposed to address the knowledge gaps in current data center energy models. The research aims to provide policy makers and data center energy analysts with comprehensive understanding of data center energy use and efficiency opportunities and a better understanding of macro-level data center energy demand and energy saving potentials, in addition to the technological barriers for adopting energy efficiency measures.
Failing to Learn: Autonomously Identifying Perception Failures for Self-Driving Cars

One of the major open challenges in self-driving cars is the ability to detect cars and pedestrians to safely navigate in the world. Deep learning-based object detector approaches have enabled great advances in using camera imagery to detect and classify objects. But for a safety critical application, such as autonomous driving, the error rates of the current state of the art are still too high to enable safe operation. Moreover, the characterization of object detector performance is primarily limited to testing on prerecorded datasets. Errors that occur on novel data go undetected without additional human labels. In this letter, we propose an automated method to identify mistakes made by object detectors without ground truth labels . We show that inconsistencies in the object detector output between a pair of similar images can be used as hypotheses for false negatives (e.g., missed detections) and using a novel set of features for each hypothesis, an off-the-shelf binary classifier can be used to find valid errors. In particular, we study two distinct cues– temporal and stereo inconsistencies—using data that are readily available on most autonomous vehicles. Our method can be used with any camera-based object detector and we illustrate the technique on several sets of real world data. We show that a state-of-the-art detector, tracker, and our classifier trained only on synthetic data can identify valid errors on KITTI tracking dataset with an average precision of 0.94. We also release a new tracking dataset with 104 sequences totaling 80,655 labeled pairs of stereo images along with ground truth disparity from a game engine to facilitate further research.
There is no degree map for 0-cycles on Artin stacks

We show that there is no way to define degrees of 0-cycles on Artin stacks with proper good moduli spaces so that (1) the degree of an ordinary point is non-zero, and (1) degrees are compatible with closed immersions.
On the monotonicity of the expected volume of a random simplex

Let a random simplex in a d-dimensional convex body be the convex hull of d+1 random points from the body. We study the following question: As a function of the convex body, is the expected volume of a random simplex monotone non-decreasing under inclusion? We show that this holds if d is 1 or 2, and does not hold if d ≥ 4. We also prove similar results for higher moments of the volume of a random simplex, in particular for the second moment, which corresponds to the determinant of the covariance matrix of the convex body. These questions are motivated by the slicing conjecture.
The Spectrum of a Harmonic Oscillator Operator Perturbed by Point Interactions

We consider the operator $Ly = - (d/dx)^{2}y + x^{2} y + w(x) y, \quad y \text { in} L^{2}(\mathbb {R}),$ where $w(x) = s \delta (x - b) + t \delta (x + b) , \quad b \neq 0 \, \, \text {real}, \quad s, t \in \mathbb {C}$ . This operator has a discrete spectrum: eventually the eigenvalues are simple. Their asymptotic is given. In particular, if s=−t, $\lambda _{n} = (2n + 1) + s^{2}\, \frac {\kappa (n)}{n} + \rho (n) \label {eq:abstractlam}$ where $\kappa (n) = \frac {1}{2\pi } \left [(-1)^{n + 1} \sin \left (2 b \sqrt {2n} \right ) - \frac {1}{2} \sin \left (4 b \sqrt {2n} \right ) \right ]$ and $\vert \rho (n) \vert \leq C \frac {\log n}{n^{3/2}}. \label {eq:abstracterr}$ If $\overline {s} = -t$ , the number T(s) of non-real eigenvalues is finite, and $T(s) \leq \left (C (1 + \vert s \vert ) \log (e + \vert s \vert ) \right )^{2}$ . The analogue of the above asymptotic is given in the case of any two-point interaction perturbation.
Stability of Vortex Solutions to an Extended Navier-Stokes System

We study the long-time behavior an extended Navier-Stokes system in R where the incompressibility constraint is relaxed. This is one of several “reduced models” of Grubb and Solonnikov ’89 and was revisited recently (Liu, Liu, Pego ’07) in bounded domains in order to explain the fast convergence of certain numerical schemes (Johnston, Liu ’04). Our first result shows that if the initial divergence of the fluid velocity is mean zero, then the Oseen vortex is globally asymptotically stable. This is the same as the Gallay Wayne ’05 result for the standard NavierStokes equations. When the initial divergence is not mean zero, we show that the analogue of the Oseen vortex exists and is stable under small perturbations. For completeness, we also prove global well-posedness of the system we study.
Isospin Lattice Gas Model and Nuclear-Matter Phase Diagram and Pressure-Volume Isotherms

We study a cubic lattice gas model for nuclear matter where each lattice site can be either occupied, by one proton or one neutron, or unoccupied. A nearest-neighbor interaction of the form - ∑ Jijτziτzj is assumed. Our model is an isospin-1 Ising model, with τz= (1, 0, –1) representing respectively (proton, vacancy, neutron). A kinetic-energy term has been included in our model. Under the Bragg-Williams mean-field approximation our model exhibits the existence of a dense phase (liquid-like) and a rare phase (gas-like). The nuclear-matter p−v isotherms given by our model are discussed.
Coordinated Assembly of Brightest Cluster Galaxies

Brightest Cluster Galaxies (BCGs) in massive dark matter halos are shaped by complex merging processes. We present a detailed stellar population analysis in the central region of Abell 3827 at $z\sim0.1$, including five-nucleus galaxies involved in a BCG assembly. Based on deep spectroscopy from Multi Unit Spectroscopic Explorer (MUSE), we fit the optical spectra of 13 early-type galaxies (ETGs) in the central 70 kpc of the cluster. The stellar populations in the central $R=1$ kpc of these ETGs are old (6-10 Gyr). Their [Fe/H] increases with $\sigma_{\star}$ and stellar mass. More importantly, [$\alpha$/Fe] of galaxies close to the cluster center do not seem to depend on $\sigma_{\star}$ or stellar mass, indicating that the cluster center shapes the [$\alpha$/Fe]-$\sigma_{\star}$ and [$\alpha$/Fe]-$M_{\star}$ relations differently than other environments where [$\alpha$/Fe] is observed to increase with increasing $\sigma_{\star}$ or $M_{\star}$. Our results reveal the coordinated assembly of BCGs: their building blocks are different from the general low mass populations by their high [$\alpha$/Fe]. Massive galaxies thus grow by accreting preferentially high [$\alpha$/Fe] systems. The radial profiles also bear the imprint of the coordinated assembly. Their declining [Fe/H] and flat [$\alpha$/Fe] radial profiles confirm that the accreted systems have low metallicity and high [$\alpha$/Fe] stellar contents.
The holographic shape of entanglement and Einstein’s equations

We study shape-deformations of the entanglement entropy and the modular Hamiltonian for an arbitrary subregion and state (with a smooth dual geometry) in a holographic conformal field theory. More precisely, we study a double-deformation comprising of a shape deformation together with a state deformation, where the latter corresponds to a small change in the bulk geometry. Using a purely gravitational identity from the Hollands-Iyer-Wald formalism together with the assumption of equality between bulk and boundary modular flows for the original, undeformed state and subregion, we rewrite a purely CFT expression for this double deformation of the entropy in terms of bulk gravitational variables and show that it precisely agrees with the Ryu-Takayanagi formula including quantum corrections. As a corollary, this gives a novel, CFT derivation of the JLMS formula for arbitrary subregions in the vacuum, without using the replica trick. Finally, we use our results to give an argument that if a general, asymptotically AdS spacetime satisfies the Ryu-Takayanagi formula for arbitrary subregions, then it must necessarily satisfy the non-linear Einstein equation.
Operator product expansion of higher rank Wilson loops from D-branes and matrix models

In this paper we study correlation functions of circular Wilson loops in higher dimensional representations with chiral primary operators of = 4 super Yang-Mills theory. This is done using the recently established relation between higher rank Wilson loops in gauge theory and D-branes with electric fluxes in supergravity. We verify our results with a matrix model computation, finding perfect agreement in both the symmetric and the antisymmetric case.
HOW BRIGHT ARE THE GAPS IN CIRCUMBINARY DISK SYSTEMS

When a circumbinary disk surrounds a binary whose secondary's mass is at least the primary's mass, a nearly empty cavity with radius a few times the binary separation is carved out of the disk. Narrow streams of material pass from the inner edge of the circumbinary disk into the domain of the binary itself, where they eventually join onto the small disks orbiting the members of the binary. Using data from three-dimensional magnetohydrodynamics simulations of this process, we determine the luminosity of these streams; it is mostly due to weak laminar shocks, and is in general only a few percent of the luminosity of adjacent regions of either the circumbinary disk or the "mini-disks." This luminosity therefore hardly affects the deficit in the thermal continuum predicted on the basis of a perfectly dark gap region.
Uniqueness of values of Aronsson operators and running costs in “tug-of-war” games

Let AH be the Aronsson operator associated with a Hamiltonian H(x,z,p). Aronsson operators arise from L∞ variational problems, two person game theory, control problems, etc. In this paper, we prove, under suitable conditions, that if u∈Wloc1,∞(Ω) is simultaneously a viscosity solution of both of the equations (0.1)AH(u)=f(x)andAH(u)=g(x)in Ω, where f,g∈C(Ω), then f=g. The assumption u∈Wloc1,∞(Ω) can be relaxed to u∈C(Ω) in many interesting situations. Also, we prove that if f,g,u∈C(Ω) and u is simultaneously a viscosity solution of the equations (0.2)Δ∞u|Du|2=−f(x)andΔ∞u|Du|2=−g(x)in Ω, then f=g. This answers a question posed in Peres, Schramm, Scheffield and Wilson [Y. Peres, O. Schramm, S. Sheffield, D.B. Wilson, Tug-of-war and the infinity Laplacian, J. Amer. Math. Soc. Math. 22 (2009) 167–210] concerning whether or not the value function uniquely determines the running cost in the “tug-of-war” game.
Using simplicial volume to count maximally broken Morse trajectories

Given a closed Riemannian manifold of dimension n and a Morse–Smale function, there are finitely many n–part broken trajectories of the negative gradient flow. We show that if the manifold admits a hyperbolic metric, then the number of n–part broken trajectories is always at least the hyperbolic volume. The proof combines known theorems in Morse theory with lemmas of Gromov about simplicial volumes of stratified spaces.
CONSTRAINING THE VELA PULSAR'S RADIO EMISSION REGION USING NYQUIST-LIMITED SCINTILLATION STATISTICS

Using a novel technique, we achieve {approx}100 picoarcsec resolution and set an upper bound of less than 4 km for the characteristic size of the Vela pulsar's emission region. Specifically, we analyze flux-density statistics of the Vela pulsar at 760 MHz. Because the pulsar exhibits strong diffractive scintillation, these statistics convey information about the spatial extent of the radio emission region. We measure both a characteristic size of the emission region and the emission sizes for individual pulses. Our results imply that the radio emission altitude for the Vela pulsar at this frequency is less than 340 km.