cssi/SciSciGPT-SciSciNet huggingface dataset:
Aspects of QCD Current Algebra on a Null Plane

Abstract Consequences of QCD current algebra formulated on a light-like hyperplane are derived for the forward scattering of vector and axial–vector currents on an arbitrary hadronic target. It is shown that current algebra gives rise to a special class of sum rules that are direct consequences of the independent chiral symmetry that exists at every point on the two-dimensional transverse plane orthogonal to the lightlike direction. These sum rules are obtained by exploiting the closed, infinite-dimensional algebra satisfied by the transverse moments of null-plane axial–vector and vector charge distributions. In the special case of a nucleon target, this procedure leads to the Adler–Weisberger, Gerasimov–Drell–Hearn, Cabibbo–Radicati and Fubini–Furlan–Rossetti sum rules. Matching to the dispersion-theoretic language which is usually invoked in deriving these sum rules, the moment sum rules are shown to be equivalent to algebraic constraints on forward S -matrix elements in the Regge limit.
MASSIVE PROTOPLANETARY DISKS IN ORION BEYOND THE TRAPEZIUM CLUSTER

We present Submillimeter Array1The Submillimeter Array is a joint project between the Submillimeter Astrophysical Observatory and the Academica Sinica Institute of Astronomy and Astrophysics and is funded by the Smithsonian Institution and the Academica Sinica. observations of the 880 μm continuum emission from three circumstellar disks around young stars in Orion that lie several arcminutes ( 1 pc) north of the Trapezium cluster. Two of the three disks are in the binary system 253-1536. Silhouette disks 216-0939 and 253-1536a are found to be more massive than any previously observed Orion disks, with dust masses derived from their submillimeter emission of 0.045 M ☉ and 0.066 M ☉, respectively. The existence of these massive disks reveals that the disk mass distribution in Orion does extend to high masses, and that the truncation observed in the central Trapezium cluster is a result of photoevaporation due to the proximity of O-stars. 253-1536b has a disk mass of 0.018 M ☉, making the 253-1536 system the first optical binary in which each protoplanetary disk is massive enough to potentially form solar systems.
$G_2$-instantons, associative submanifolds, and Fueter sections

We give a sufficient condition for an associative submanifold in a G2-manifold to appear as the bubbling locus of a sequence of G2-instantons, related to the existence of a Fueter section of a bundle of ASD instanton moduli spaces over said submanifold.
Gottlieb Groups of Function Spaces

We analyse the Gottlieb groups of function spaces. Our results lead to explicit decompositions of the Gottlieb groups of many function spaces map(X, Y)—including the (iterated) free loop space of Y—directly in terms of the Gottlieb groups of Y. More generally, we give explicit decompositions of the generalised Gottlieb groups of map(X, Y) directly in terms of generalised Gottlieb groups of Y. Particular cases of our results relate to the torus homotopy groups of Fox. We draw some consequences for the classification of T-spaces and G-spaces. For X, Y finite and Y simply connected, we give a formula for the ranks of the Gottlieb groups of map(X, Y) in terms of the Betti numbers of X and the ranks of the Gottlieb groups of Y. Under these hypotheses, the Gottlieb groups of map(X, Y) are finite groups in all but finitely many degrees.
Galaxy Halo Masses from Weak Gravitational Lensing

In this review, I discuss the use of galaxy-galaxy weak lensing measurements to study the masses of dark matter halos in which galaxies reside. After summarizing how weak gravitational lensing measurements can be interpreted in terms of halo mass, I review measure- ments that were used to derive the relationship between optical galaxy mass tracers, such as stellar mass or luminosity, and dark matter halo mass. Measurements of galaxy-galaxy lensing from the past decade have led to increasingly tight constraints on the connection between dark matter halo mass and optical mass tracers, including both the mean relationships between these quantities and the intrinsic scatter between them. I also review some of the factors that can complicate analysis, such as the choice of modeling procedure, and choices made when dividing up samples of lens galaxies.
Bispectral commuting difference operators for multivariable Askey-Wilson polynomials

We construct a commutative algebra A z , generated by d algebraically independent q-difference operators acting on variables z 1 , z 2 ,..., z d , which is diagonalized by the multivariable Askey-Wilson polynomials P n (z) considered by Gasper and Rahman (2005). Iterating Sears' 4φ3 transformation formula, we show that the polynomials P n (z) possess a certain duality between z and n. Analytic continuation allows us to obtain another commutative algebra A n , generated by d algebraically independent difference operators acting on the discrete variables n 1 , n 2 ,..., n d , which is also diagonalized by P n (z). This leads to a multivariable q-Askey-scheme of bispectral orthogonal polynomials which parallels the theory of symmetric functions.
Characterization of chromium compensated GaAs as an X-ray sensor material for charge-integrating pixel array detectors

We studied the properties of chromium compensated GaAs when coupled to charge integrating ASICs as a function of detector temperature, applied bias and X-ray tube energy. The material is a photoresistor and can be biased to collect either electrons or holes by the pixel circuitry. Both are studied here. Previous studies have shown substantial hole trapping. This trapping and other sensor properties give rise to several non-ideal effects which include an extended point spread function, variations in the effective pixel size, and rate dependent offset shifts. The magnitude of these effects varies with temperature and bias, mandating good temperature uniformity in the sensor and very good temperature stabilization, as well as a carefully selected bias voltage.
Population Genetics with Fluctuating Population Sizes

Standard neutral population genetics theory with a strictly fixed population size has important limitations. An alternative model that allows independently fluctuating population sizes and reproduces the standard neutral evolution is reviewed. We then study a situation such that the competing species are neutral at the equilibrium population size but population size fluctuations nevertheless favor fixation of one species over the other. In this case, a separation of timescales emerges naturally and allows adiabatic elimination of a fast population size variable to deduce the fluctuation-induced selection dynamics near the equilibrium population size. The results highlight the incompleteness of the standard population genetics with a strictly fixed population size.
Student understanding of Taylor series expansions in statistical mechanics

One goal of physics instruction is to have students learn to make physical meaning of specific mathematical expressions, concepts, and procedures in different physical settings. As part of research investigating student learning in statistical physics, we are developing curriculum materials that guide students through a derivation of the Boltzmann factor using a Taylor series expansion of entropy. Using results from written surveys, classroom observations, and both individual think-aloud and teaching interviews, we present evidence that many students can recognize and interpret series expansions, but they often lack fluency in creating and using a Taylor series appropriately, despite previous exposures in both calculus and physics courses.
Turbulent Model of Crab Nebula Radiation

We construct a turbulent model of the Crab Nebula's non-thermal emission. The present model resolves a number of long-standing problems of the Kennel-Coroniti (1984) model: (i) the sigma problem; (ii) the hard spectrum of radio electrons; (iii) the high peak energy of gamma-ray flares; (iv) and the spacial evolution of the infrared (IR) emission. The Nebula contains two populations of injected particles: Component-I accelerated at the wind termination shock via Fermi-I mechanism, and Component-II accelerated in reconnecting turbulence in highly magnetized ($\sigma$ $\gg 1$) plasma in the central part of the Crab Nebula. The reconnecting turbulence Component-II extends from radio to gamma rays: it accelerate radio electrons with a hard spectrum, destroy the large scale magnetic flux (and thus resolves the sigma-problem), and occasionally produces gamma-ray flares (from the largest scale reconnection events). The model reproduces the broad-band spectrum of the Crab Nebula, from low-frequency synchrotron emission in radio to inverse-Compton emission at TeV energies, as well as spatially resolved evolution of the spectral indices in IR and optical bands.
The self-regulated AGN feedback loop: the role of chaotic cold accretion

Supermassive black hole accretion and feedback play central role in the evolution of galaxies, groups, and clusters. I review how AGN feedback is tightly coupled with the formation of multiphase gas and the newly probed chaotic cold accretion (CCA). In a turbulent and heated atmosphere, cold clouds and kpc-scale filaments condense out of the plasma via thermal instability and rain toward the black hole. In the nucleus, the recurrent chaotic collisions between the cold clouds, filaments, and central torus promote angular momentum cancellation or mixing, boosting the accretion rate up to 100 times the Bondi rate. The rapid variability triggers powerful AGN outflows, which quench the cooling flow and star formation without destroying the cool core. The AGN heating stifles the formation of multiphase gas and accretion, the feedback subsides and the hot halo is allowed to cool again, restarting a new cycle. Ultimately, CCA creates a symbiotic link between the black hole and the whole host via a tight self-regulated feedback which preserves the gaseous halo in global thermal equilibrium throughout cosmic time.
Implications of Mass and Energy Loss due to Coronal Mass Ejections on Magnetically Active Stars

Analysis of a database of solar coronal mass ejections (CMEs) and associated flares over the period 1996-2007 finds well-behaved power-law relationships between the 1-8 A flare X-ray fluence and CME mass and kinetic energy. We extrapolate these relationships to lower and higher flare energies to estimate the mass and energy loss due to CMEs from stellar coronae, assuming that the observed X-ray emission of the latter is dominated by flares with a frequency as a function of energy dn/dE = kE –α. For solar-like stars at saturated levels of X-ray activity, the implied losses depend fairly weakly on the assumed value of α and are very large: yr–1 and . In order to avoid such large energy requirements, either the relationships between CME mass and speed and flare energy must flatten for X-ray fluence 1031 erg, or the flare-CME association must drop significantly below 1 for more energetic events. If active coronae are dominated by flares, then the total coronal energy budget is likely to be up to an order of magnitude larger than the canonical 10–3 L bol X-ray saturation threshold. This raises the question of what is the maximum energy a magnetic dynamo can extract from a star? For an energy budget of 1% of L bol, the CME mass loss rate is about 5 × 10–11 M ☉ yr–1.
Supernova Remnant in a Stratified Medium: Explicit, Analytical Approximations for Adiabatic Expansion and Radiative Cooling

We propose simple, explicit, analytical approximations for the kinematics of an adiabatic blast wave propagating in an exponentially stratified ambient medium and for the onset of radiative cooling, which ends the adiabatic era. Our method, based on the Kompaneets implicit solution and the Kahn approximation for the radiative cooling coefficient, gives straightforward estimates for the size, expansion velocity, and progression of cooling times over the surface when applied to supernova remnants (SNRs). The remnant shape is remarkably close to spherical for moderate density gradients, but even a small gradient in ambient density causes the cooling time to vary substantially over the remnant's surface, so that for a considerable period there will be a cold dense expanding shell covering only a part of the remnant. Our approximation provides an effective tool for identifying the approximate parameters when planning two-dimensional numerical models of SNRs, the example of W44 being given in a subsequent paper.
GAUGE MODELS IN D DIMENSIONS

Utilizing the gauge framework, software under development at Baylor University, we explicitly construct all layer 1 weakly coupled free fermionic heterotic string (WCFFHS) gauge models up to order 32 in four to ten large spacetime dimensions. These gauge models are well suited to large scale systematic surveys and, while they offer little phenomenologically, are useful for understanding the structure of the WCFFHS region of the string landscape. Herein, we present the gauge groups statistics for this swath of the landscape for both supersymmetric and non-supersymmetric models.
Shape profiles and orientation bias for weak and strong lensing cluster halos

We study the intrinsic shape and alignment of isodensities of galaxy cluster halos extracted from the MultiDark MDR1 cosmological simulation. We find that the simulated halos are extremely prolate on small scales and increasingly spherical on larger ones. Due to this trend, analytical projection along the line of sight produces an overestimation of the concentration index as a decreasing function of radius, which we quantify by using both the intrinsic distribution of three-dimensional concentrations (c {sub 200}) and isodensity shape on weak and strong lensing scales. We find this difference to be ∼18% (∼9%) for low- (medium-)mass cluster halos with intrinsically low concentrations (c {sub 200} = 1-3), while we find virtually no difference for halos with intrinsically high concentrations. Isodensities are found to be fairly well aligned throughout the entirety of the radial scale of each halo population. However, major axes of individual halos have been found to deviate by as much as ∼30°. We also present a value-added catalog of our analysis results, which we have made publicly available to download.
Spatially Resolved Circumnuclear Dust in Centaurus A

In this Letter, we present results from our exploratory mid-IR study of Centaurus A circumnuclear environment using high angular resolution imaging at the Magellan 6.5 m telescope with the MIRAC/BLINC camera. We detected emission from a compact region surrounding the nuclear source and obtained photometry at 8.8 μm and in the N band. Our analysis suggests that the nuclear region is resolved with a size of ≈3 pc. The mid-IR emission from this region is likely associated with cool dust with an estimated temperature of ~160 K, surrounding the central "hidden" active galactic nucleus (AGN). We discuss the characteristics of this emission in relation to other mid-IR observations and the implications on models of dust formation in AGNs.
Asteroid Evolution: Role of Geotechnical Properties

This paper presents a brief review and latest results of the work that has been carried out by the Planetary Science community in order to understand the role of the geotechnical properties of granular asteroids (commonly known as “rubble-pile” asteroids) in their formation, evolution and possible disruption. As such, we will touch in aspects of the theoretical and numerical tools that have been used with this objective and how the obtained results compare to the observed asteroids.
Superconductivity in Striped and Multi-Fermi-Surface Hubbard Models: From the Cuprates to the Pnictides

Single- and multiband Hubbard models have been found to describe many of the complex phenomena that are observed in the cuprate and iron-based high-temperature superconductors. Simulations of these models therefore provide an ideal framework to study and understand the superconducting properties of these systems and the mechanisms responsible for them. Here, we review recent dynamic cluster quantum Monte Carlo simulations of these models, which provide an unbiased view of the leading correlations in the system. In particular, we discuss what these simulations tell us about superconductivity in the homogeneous 2D single-orbital Hubbard model, and how charge stripes affect this behavior. We then describe recent simulations of a bilayer Hubbard model, which provides a simple model to study the type and nature of pairing in systems with multiple Fermi surfaces such as the iron-based superconductors.
Efficient high-order singular quadrature schemes in magnetic fusion

Several problems in magnetically confined fusion, such as the computation of exterior vacuum fields or the decomposition of the total magnetic field into separate contributions from the plasma and the external sources, are best formulated in terms of integral equation expressions. Based on Biot-Savart-like formulae, these integrals contain singular integrands. The regularization method commonly used to address the computation of various singular surface integrals along general toroidal surfaces is low-order accurate, and therefore requires a dense computational mesh in order to obtain sufficient accuracy. In this work, we present a fast, high-order quadrature scheme for the efficient computation of these integrals. Several numerical examples are provided demonstrating the computational efficiency and the high-order accurate convergence. A corresponding code for use in the community has been publicly released.
FreaAI: Automated Extraction of Data Slices to Test Machine Learning Models

Although machine learning (ML) solutions are prevalent, in order for them to be truly ‘business-grade’ and reliable, their performance must be shown to be robust for many different data subsets observations with similar feature values (which we call ‘slices’) which they are expected to encounter in deployment. However, ML solutions are often evaluated only based on aggregate performance (e.g., overall accuracy) and not on the variability on various slices. For example, a text classifier deployed on bank terms may have very high accuracy (e.g., \(98\% \pm 2\%\)) but might perform poorly for the data slice of terms that include short descriptions and originate from commercial accounts. Yet a business requirement may be for the classifier to perform well regardless of the text characteristics. In previous work [1] we demonstrated the effectiveness of using feature-based analysis to highlight such gaps in performance assessment. Here we demonstrate a novel technique, called IBM FreaAI, which automatically extracts explainable feature slices for which the ML solution’s performance is statistically significantly worse than the average. We demonstrate results of evaluating ML classifier models on seven open datasets.
Self cup products and the theta characteristic torsor

We give a general formula relating self cup products in cohomology to connecting maps in nonabelian cohomology, and apply it to obtain a formula for the self cup product associated to the Weil pairing.
Can compactifications solve the cosmological constant problem

Recently, there have been claims in the literature that the cosmological constant problem can be dynamically solved by specific compactifications of gravity from higher-dimensional toy models. These models have the novel feature that in the four-dimensional theory, the cosmological constant Λ is much smaller than the Planck density and in fact accumulates at Λ = 0. Here we show that while these are very interesting models, they do not properly address the real cosmological constant problem. As we explain, the real problem is not simply to obtain Λ that is small in Planck units in a toy model, but to explain why Λ is much smaller than other mass scales (and combinations of scales) in the theory. Instead, in these toy models, all other particle mass scales have been either removed or sent to zero, thus ignoring the real problem. To this end, we provide a general argument that the included moduli masses are generically of order Hubble, so sending them to zero trivially sends the cosmological constant to zero. We also show that the fundamental Planck mass is being sent to zero, and so the central problem is trivially avoided by removing high energy physics altogether. On the other hand, by including various large mass scales from particle physics with a high fundamental Planck mass, one is faced with a real problem, whose only known solution involves accidental cancellations in a landscape.
Exact coherent states with hairpin-like vortex structure in channel flow

Hairpin vortices are widely studied as an important structural aspect of wall turbulence. The present work describes, for the first time, nonlinear travelling wave solutions to the Navier–Stokes equations in the channel flow geometry – exact coherent states (ECS) – that display hairpin-like vortex structure. This solution family comes into existence at a saddle-node bifurcation at Reynolds number . At the bifurcation, the solution has a highly symmetric quasi-streamwise vortex structure similar to that reported for previously studied ECS. With increasing distance from the bifurcation, however, both the upper and lower branch solutions develop a vortical structure characteristic of hairpins: a spanwise-oriented ‘head’ near the channel centreplane where the mean shear vanishes connected to counter-rotating quasi-streamwise ‘legs’ that extend toward the channel wall. At , the upper branch solution has mean and Reynolds shear-stress profiles that closely resemble those of turbulent mean profiles in the same domain.
A Bayesian Approach to Comparing Cosmic Ray Energy Spectra

A common problem in ultra-high energy cosmic ray physics is the comparison of energy spectra. The question is whether the spectra from two experiments or two regions of the sky agree within their statistical and systematic uncertainties. We develop a method to directly compare energy spectra for ultra-high energy cosmic rays from two different regions of the sky in the same experiment without reliance on agreement with a theoretical model of the energy spectra. The consistency between the two spectra is expressed in terms of a Bayes factor, defined here as the ratio of the likelihood of the two-parent source hypothesis to the likelihood of the one-parent source hypothesis. Unlike other methods, for example χ2 tests, the Bayes factor allows for the calculation of the posterior odds ratio and correctly accounts for non-Gaussian uncertainties. The latter is particularly important at the highest energies, where the number of events is very small.
Separability in cohomogeneity-2 Kerr-NUT-AdS metrics

The remarkable and unexpected separability of the Hamilton-Jacobi and Klein-Gordon equations in the background of a rotating four-dimensional black hole played an important role in the construction of generalisations of the Kerr metric, and in the uncovering of hidden symmetries associated with the existence of Killing tensors. In this paper, we show that the Hamilton-Jacobi and Klein-Gordon equations are separable in Kerr-AdS backgrounds in all dimensions, if one specialises the rotation parameters so that the metrics have cohomogeneity 2. Furthermore, we show that this property of separability extends to the NUT generalisations of these cohomogeneity-2 black holes that we obtained in a recent paper. In all these cases, we also construct the associated irreducible rank-2 Killing tensor whose existence reflects the hidden symmetry that leads to the separability. We also consider some cohomogeneity-1 specialisations of the new Kerr-NUT-AdS metrics, showing how they relate to previous results in the literature.
Surveying the hard X‐ray sky: imaging in space and time

One of the few remaining astronomical bands (factor of ∽ 10 in energy range) still without an all-sky imaging survey is the hard x-ray band (10–600 keV). This is in spite of sensitive imaging all- sky surveys already conducted at soft x-ray (0.2-2 keV; ROSAT) and soft/hard γ-ray (∽750 keV - 10 GeV; COMPTEL/EGRET) energies and imminent for medium x-ray energies (2–10 keV; ABRIXAS). A hard x-ray imaging survey conducted with wide-field coded aperture telescopes allows both hight sensitivity (and spatial/spectral resolution) and broad temporal coverage. We derive a generalized survey sensitivity/temporal parameter, Q, and compare previous and planned hard x-ray surveys with the proposed EXIST mission. Key scientific objectives that could be addressed with the enhanced capability of EXIST are outlined.
Shot noise in non-adiabatically driven nanoscale conductors

We investigate the noise properties of pump currents through molecular wires and coupled quantum dots. As a model we employ a two-level system that is connected to electron reservoirs and is non-adiabatically driven. Concerning the electron-electron interaction, we focus on two limits: non-interacting electrons and strong Coulomb repulsion. While the former case is treated within a Floquet scattering formalism, we derive for the latter case a master equation formalism for the computation of the current and the zero-frequency noise. For a pump operated close to internal resonances, the differences between the non-interacting and the strongly interacting limit turn out to be surprisingly small.
On the Apparent Associations Between Interstellar Neutral Hydrogen Structure and (WMAP) High-frequency Continuum Emission

Galactic neutral hydrogen (H I) within a few hundred parsecs of the Sun contains structure with an angular distribution that is similar to small-scale structure observed by the Wilkinson Microwave Anisotropy Probe (WMAP). A total of 108 associated pairs of associated H I and WMAP features have now been cataloged using H I data mapped in 2 km s–1 intervals and these pairs show a typical offset of 08. A large-scale statistical test for a direct association is carried out that casts little additional light on whether the these small offsets are merely coincidental or carry information. To pursue the issue further, the nature of several of the features within the foreground H I most closely associated with WMAP structure is examined in detail and it is shown that the cross-correlation coefficient for well-matched pairs of structures is of order unity. It is shown that free-free emission from electrons in unresolved density enhancements in interstellar space could theoretically produce high-frequency radio continuum radiation at the levels observed by WMAP and that such emission will appear nearly flat across the WMAP frequency range. Evidence for such structure in the interstellar medium already exists in the literature. Until higher angular resolution observations of the high-frequency continuum emission structure as well as the apparently associated H I structure become available, it may be difficult to rule out the possibility that some if not all the small-scale structure usually attributed to the cosmic microwave background may have a galactic origin.
massclean (MASSive CLuster Evolution and ANalysis Package): description, tests, and results

MASSCLEAN is a new, sophisticated and robust stellar cluster image and photometry simulation package. This package is able to create color-magnitude diagrams and standard FITS images in any of the traditional optical and near-infrared bands based on cluster characteristics input by the user, including but not limited to distance, age, mass, radius and extinction. At the limit of very distant, unresolved clusters, we have checked the integrated colors created in MASSCLEAN against those from other simple stellar population (SSP) models with consistent results. Because the algorithm populates the cluster with a discrete number of tenable stars, it can be used as part of a Monte Carlo Method to derive the probabilistic range of characteristics (integrated colors, for example) consistent with a given cluster mass and age. We present the first ever mass dependent integrated colors as a function of age, derived from over 100,000 Monte Carlo runs, which can be used to improve the current age determination methods for stellar clusters.
AN M DWARF COMPANION AND ITS INDUCED SPIRAL ARMS IN THE HD 100453 PROTOPLANETARY DISK

Recent VLT/SPHERE near-infrared imaging observations revealed two spiral arms with a near m = 2 rotational symmetry in the protoplanetary disk around the ~1.7 M⊙ Herbig star HD 100453. A ~0.3 M⊙ M dwarf companion, HD 100453 B, was also identified at a projected separation of 120 AU from the primary. In this Letter, we carry out hydrodynamic and radiative transfer simulations to examine the scattered light morphology of the HD 100453 disk as perturbed by the companion on a circular and coplanar orbit. We find that the companion truncates the disk at ~45 AU in scattered light images, and excites two spiral arms in the remaining (circumprimary) disk with a near m = 2 rotational symmetry. Both the truncated disk size and the morphology of the spirals are in excellent agreement with the SPHERE observations at Y, J, H, and K1-bands, suggesting that the M dwarf companion is indeed responsible for the observed double-spiral-arm pattern. Our model suggests that the disk is close to face on (inclination angle ~5°), and that the entire disk-companion system rotates counterclockwise on the sky. The HD 100453 observations, along with our modeling work, demonstrate that double spiral arm patterns in near-infrared scattered light images can be generically produced by companions, and support future observations to identify the companions responsible for the arms observed in the MWC 758 and SAO 206462 systems.
Index-like theorems from line defect vevs

In this paper we investigate the relation between complexified Fenchel-Nielsen coordinates and spectral network coordinates on Seiberg-Witten moduli space. The main technique is the comparison of exact expressions for the expectation value of ’t Hooft defects in certain 4D SU(2) $$ \mathcal{N} $$ = 2 gauge theories. We derive an index-like theorem for a class of Dirac operators on singular monopole moduli spaces. Our expression determines the indices of Dirac operators on singular monopole moduli spaces in terms of characteristic numbers for vector bundles over certain Kronheimer-Nakajima quiver varieties.
LCOGT network observatory operations

We describe the operational capabilities of the Las Cumbres Observatory Global Telescope Network. We summarize our hardware and software for maintaining and monitoring network health. We focus on methodologies to utilize the automated system to monitor availability of sites, instruments and telescopes, to monitor performance, permit automatic recovery, and provide automatic error reporting. The same jTCS control system is used on telescopes of apertures 0.4m, 0.8m, 1m and 2m, and for multiple instruments on each. We describe our network operational model, including workloads, and illustrate our current tools, and operational performance indicators, including telemetry and metrics reporting from on-site reductions. The system was conceived and designed to establish effective, reliable autonomous operations, with automatic monitoring and recovery - minimizing human intervention while maintaining quality. We illustrate how far we have been able to achieve that.
On the Origin of Dynamically Isolated Hot Earths

A distinct population of planetary systems that contain dynamically isolated, Earth-size planets with orbital periods $P_\mathrm{orb}\sim 1\,$day was recently identified in an analysis of data from the Kepler planet candidate catalog. We argue that these objects could represent the remnant rocky cores of giant planets that arrived at the stellar vicinity on high-eccentricity orbits and were rapidly stripped of their gaseous envelopes after crossing their respective Roche limits (RLs) $a_\mathrm{R,p}$. In this picture, objects with $P_\mathrm{orb}\gtrsim1\,$day are mostly "early" cores that originated in planets with an initial periastron distance $a_\mathrm{per,0}\le a_\mathrm{R,p}$; they had high initial eccentricities but their orbits underwent fast tidal circularization after the cores were exposed. Objects with $P_\mathrm{orb}\lesssim 1\,$day are, by contrast, mostly "late" cores that originated in planets with $a_\mathrm{per,0}>a_\mathrm{R,p}$; these planets underwent orbital circularization to a radius $>a_\mathrm{per,0}$ but eventually reached $a_\mathrm{R,p}$ through tidal orbital decay. This picture naturally accounts for the spatial distribution of hot Earths and for the similarity of their inferred occurrence rate to that of hot Jupiters, and it fits well with the interpretation of the so-called sub-Jovian desert in the orbital-period--planetary-mass plane in terms of high-eccentricity planet migration to the vicinity of the RL.
Infection Analysis on Irregular Networks Through Graph Signal Processing

In a networked system, functionality can be seriously endangered when nodes are infected , due to either internal random failures or a contagious virus that develops into an epidemic. Given a snapshot of the network representing the nodes’ states (infected or healthy), infection analysis refers to distinguishing an epidemic from random failures and gathering information for effective countermeasure design. This analysis is challenging due to irregular network structure, heterogeneous epidemic spreading, and noisy observations. This article treats a network snapshot as a graph signal , and develops effective approaches for infection analysis based on graph signal processing. For the macro (network-level) analysis aiming to distinguish an epidemic from random failures, i) multiple detection metrics are defined based on the graph Fourier transform (GFT) and neighborhood characteristics of the graph signal; ii) a new class of graph wavelets, distance-based graph wavelets (DBGWs), are developed; and iii) a machine learning-based framework is designed employing either the GFT spectrum or the graph wavelet coefficients as features for infection analysis. DBGWs also enable the micro (node-level) infection analysis, through which the performance of epidemic countermeasures can be improved. Extensive simulations are conducted to demonstrate the effectiveness of all the proposed algorithms in various network settings.
Fundamental physics from the sky: Cosmic rays, gamma rays and the hunt for dark matter

Can we learn about New Physics with astronomical and astro–particle data? Understanding how this is possible is key to unraveling one of the most pressing mysteries at the interface of cosmology and particle physics: the fundamental nature of dark matter. I will discuss some of the recent puzzling findings in cosmic–ray electron–positron data and in gamma–ray observations that might be related to dark matter. I will argue that recent cosmic–ray data, most notably from the Pamela and Fermi satellites, indicate that previously unaccounted–for powerful sources in the Galaxy inject high–energy electrons and positrons. Interestingly, this new source class might be related to new fundamental particle physics, and specifically to pair–annihilation or decay of galactic dark matter. This exciting scenario is directly constrained by Fermi gamma–ray observations, which also inform us on astrophysical source counterparts that could also be responsible for the high–energy electron–positron excess. Observations of gamma–ray emission from the central regions of the Galaxy as well as claims on a gamma–ray line at around 130 GeV also recently triggered a wide–spread interest: I will address the question of whether we are really observing signals from dark matter annihilation, how to test this hypothesis, and which astrophysical mechanisms constitute the relevant background.
New Theories With Quantum Modified Moduli Space

Kutasov-type duals of supersymmetric gauge theories had been studied only in the dual regime and the s-confining case. Here we extend the discussion to the case of less flavor, analogous to the case of quantum-modified moduli space in Seiberg duality. Unlike the Seiberg duality, however, we find that parts of the moduli space become superconformal, generalizing the so far isolated example of SU(2) theory with two doublets and a triplet. We also point out that the magnetic superpotential needs to be augmented by an additional instanton-generated piece when the magnetic group is SU(2).
Reanalysis of the radii of the Benchmark eclipsing binary V578 Mon

V578 Mon is an eclipsing binary system in which both stars have masses above 10 M ☉ determined with an accuracy better than 3%. It is one of only five such massive eclipsing binaries known that also possess eccentric orbits and measured apsidal motions, thus making it an important benchmark for theoretical stellar evolution models. However, recently reported determinations of the radii of V578 Mon differ significantly from previously reported values. We reanalyze the published data for V578 Mon and trace the discrepancy to the use of an incorrect formulation for the stellar potentials in the most recent analysis. Here we report corrected radii for this important benchmark eclipsing binary.
Testing Angular Momentum Transport and Wind Loss in Intermediate-mass Core-helium Burning Stars

Stars between two and three solar masses rotate rapidly on the main sequence, and their rotation rates in the core helium burning (secondary clump) phase can therefore be used to test models of angular momentum loss used for gyrochronology in a new regime. Because both their core and surface rotation rates can be measured, these stars can also be used to set strong constraints on angular momentum transport inside stars. We find that they are rotating slower than angular momentum conservation and rigid rotation would predict. Our results are insensitive to the degree of core-envelope coupling because of the small moment of inertia of the radiative core. We discuss two possible mechanisms for slowing down the surfaces of these stars: (1) substantial angular momentum loss, and (2) radial differential rotation in the surface convection zone. Modern angular momentum loss prescriptions used for solar-type stars predict secondary clump surface rotation rates in much better agreement with the data than prior variants used in the literature, and we argue that such enhanced loss is required to understand the combination of core and surface rotation rates. However, we find that the assumed radial differential rotation profile in convective regions has a strong impact on the predicted surface rotation rates, and that a combination of enhanced loss and radial differential rotation in the surface convection zone is also consistent with the data. We discuss future tests that can quantify the impact of both phenomena. Current data tentatively suggests that some combination of the two processes fits the data better than either one alone.
Differential Scene Flow from Light Field Gradients

This paper presents novel techniques for recovering 3D dense scene flow, based on differential analysis of 4D light fields. The key enabling result is a per-ray linear equation, called the ray flow equation, that relates 3D scene flow to 4D light field gradients. The ray flow equation is invariant to 3D scene structure and applicable to a general class of scenes, but is under-constrained (3 unknowns per equation). Thus, additional constraints must be imposed to recover motion. We develop two families of scene flow algorithms by leveraging the structural similarity between ray flow and optical flow equations: local ‘Lucas–Kanade’ ray flow and global ‘Horn–Schunck’ ray flow, inspired by corresponding optical flow methods. We also develop a combined local–global method by utilizing the correspondence structure in the light fields. We demonstrate high precision 3D scene flow recovery for a wide range of scenarios, including rotation and non-rigid motion. We analyze the theoretical and practical performance limits of the proposed techniques via the light field structure tensor, a $$3 \times 3$$ matrix that encodes the local structure of light fields. We envision that the proposed analysis and algorithms will lead to design of future light-field cameras that are optimized for motion sensing, in addition to depth sensing.
Semantic Mapping for Orchard Environments by Merging Two-Sides Reconstructions of Tree Rows

Measuring semantic traits for phenotyping is an essential but labor-intensive activity in horticulture. Researchers often rely on manual measurements which may not be accurate for tasks such as measuring tree volume. To improve the accuracy of such measurements and to automate the process, we consider the problem of building coherent three dimensional (3D) reconstructions of orchard rows. Even though 3D reconstructions of side views can be obtained using standard mapping techniques, merging the two side-views is difficult due to the lack of overlap between the two partial reconstructions. Our first main contribution in this paper is a novel method that utilizes global features and semantic information to obtain an initial solution aligning the two sides. Our mapping approach then refines the 3D model of the entire tree row by integrating semantic information common to both sides, and extracted using our novel robust detection and fitting algorithms. Next, we present a vision system to measure semantic traits from the optimized 3D model that is built from the RGB or RGB-D data captured by only a camera. Specifically, we show how canopy volume, trunk diameter, tree height and fruit count can be automatically obtained in real orchard environments. The experiment results from multiple datasets quantitatively demonstrate the high accuracy and robustness of our method.
The circular law for random regular digraphs with random edge weights

We consider random n × n matrices of the form Yn = 1 dAn ∘ Xn, where An is the adjacency matrix of a uniform random d-regular directed graph on n vertices, with d = ⌊pn⌋ for some fixed p ∈ (0, 1), and Xn is an n × n matrix of i.i.d. centered random variables with unit variance and finite (4 + η)th moment (here ∘ denotes the matrix Hadamard product). We show that as n →∞, the empirical spectral distribution of Yn converges weakly in probability to the normalized Lebesgue measure on the unit disk.
SUPPRESSION OF FIBER MODAL NOISE INDUCED RADIAL VELOCITY ERRORS FOR BRIGHT EMISSION-LINE CALIBRATION SOURCES

Modal noise in optical fibers imposes limits on the signal-to-noise ratio (S/N) and velocity precision achievable with the next generation of astronomical spectrographs. This is an increasingly pressing problem for precision radial velocity spectrographs in the near-infrared (NIR) and optical that require both high stability of the observed line profiles and high S/N. Many of these spectrographs plan to use highly coherent emission-line calibration sources like laser frequency combs and Fabry-Perot etalons to achieve precision sufficient to detect terrestrial-mass planets. These high-precision calibration sources often use single-mode fibers or highly coherent sources. Coupling light from single-mode fibers to multi-mode fibers leads to only a very low number of modes being excited, thereby exacerbating the modal noise measured by the spectrograph. We present a commercial off-the-shelf solution that significantly mitigates modal noise at all optical and NIR wavelengths, and which can be applied to spectrograph calibration systems. Our solution uses an integrating sphere in conjunction with a diffuser that is moved rapidly using electrostrictive polymers, and is generally superior to most tested forms of mechanical fiber agitation. We demonstrate a high level of modal noise reduction with a narrow bandwidth 1550 nm laser. Our relatively inexpensive solution immediately enables spectrographs to take advantage of the innate precision of bright state-of-the art calibration sources by removing a major source of systematic noise.
An energy-efficient reconfigurable DTLS cryptographic engine for End-to-End security in iot applications

End-to-end security protocols, like Datagram Transport Layer Security (DTLS) [1], enable the establishment of mutually authenticated confidential channels between edge nodes and the cloud, even in the presence of untrusted and potentially malicious network infrastructure. While this makes DTLS an ideal solution for IoT, the associated computational cost makes software-only implementations prohibitively expensive for resource-constrained embedded devices. We address this challenge through three key contributions: reconfigurable cryptographic accelerators enable two orders of magnitude energy savings, a dedicated DTLS engine offloads control flow to hardware reducing program code and memory usage by ∼10x, and an on-chip RISC-V core exercises the flexibility of the cryptographic accelerators to demonstrate security applications beyond DTLS.
(Information) Paradox Regained? A Brief Comment on Maudlin on Black Hole Information Loss

We discuss some recent work by Tim Maudlin concerning Black Hole Information Loss. We argue, contra Maudlin, that there is a paradox, in the straightforward sense that there are propositions that appear true, but which are incompatible with one another. We discuss the significance of the paradox and Maudlin’s response to it.
An ultraviolet investigation of activity on exoplanet host stars

Using the far-UV (FUV) and near-UV (NUV) photometry from the NASA Galaxy Evolution Explorer (GALEX), we searched for evidence of increased stellar activity due to tidal and/or magnetic star-planet interactions (SPI) in the 272 known FGK planetary hosts observed by GALEX. With the increased sensitivity of GALEX, we are able probe systems with lower activity levels and at larger distances than what has been done to date with X-ray satellites. We compared samples of stars with close-in planets (a 0.5 AU) and looked for correlations of excess activity with other system parameters. This statistical investigation found no clear correlations with a, Mp , or Mp /a, in contrast to some X-ray and Ca II studies. However, there is tentative evidence (at a level of 1.8σ) that stars with radial-velocity-(RV)-detected close-in planets are more FUV-active than stars with far-out planets, in agreement with several published X-ray and Ca II results. The case is strengthened to a level of significance to 2.3σ when transit-detected close-in planets are included. This is most likely because the RV-selected sample of stars is significantly less active than the field population of comparable stars, while the transit-selected sample is similarly active. Given the factor of 2-3 scatter in fractional FUV luminosity for a given stellar effective temperature, it is necessary to conduct a time-resolved study of the planet hosts in order to better characterize their UV variability and generate a firmer statistical result.
Enumeration of Bigrassmannian Permutations Below a Permutation in Bruhat Order

In theory of Coxeter groups, bigrassmannian elements are well known as elements which have precisely one left descent and precisely one right descent. In this article, we prove formulas on enumeration of bigrassmannian permutations weakly below a permutation in Bruhat order in the symmetric groups. For the proof, we use equivalent characterizations of bigrassmannian permutations by Lascoux-Schutzenberger and Reading.
Covert Capacity of Bosonic Channels

We investigate the quantum-secure covert-communication capabilities of lossy thermal-noise bosonic channels, the quantum-mechanical model for many practical channels. We determine the expressions for the covert capacity of these channels: $L_{no-EA}$ , when Alice and Bob share only a classical secret, and $L_{EA}$ , when they benefit from entanglement assistance. We find that entanglement assistance alters the fundamental scaling law for covert communication. Instead of $L_{no-EA}\sqrt {n}-r_{no-EA}(n)$ , $r_{no-EA}(n)=o(\sqrt {n})$ , entanglement assistance allows $L_{EA}\sqrt {n}\log n-r_{EA}(n)$ , $r_{EA}(n)=o(\sqrt {n}\log n)$ , covert bits to be transmitted reliably over $n$ channel uses.
When pull turns to shove: A continuous-time model for opinion dynamics

The authors develop a framework for political behavior of a population influenced by a heterogeneous environment in continuous time, incorporating tribalism and repulsion from dissonant ideas.