cssi/SciSciGPT-SciSciNet huggingface dataset:
Spectral Evolution Models for the Next Decade

Spectral evolution models are a widely used tool for determining the stellar content of galaxies. I provide a review of the latest developments in stellar atmosphere and evolution models, with an emphasis on massive stars. In contrast to the situation for low- and intermediate mass stars, the current main challenge for spectral synthesis models are the uncertainties and rapid revision of current stellar evolution models. Spectral libraries, in particular those drawn from theoretical model atmospheres for hot stars, are relatively mature and can complement empirical templates for larger parameter space coverage. I introduce a new ultraviolet spectral library based on theoretical radiation-hydrodynamic atmospheres for hot massive stars. Application of this library to star-forming galaxies at high redshift, i.e., Lyman-break galaxies, will provide new insights into the abundances, initial mass function and ages of stars in the very early universe.
An Energy-Based Comparison of Long-Hop and Short-Hop Routing in MIMO Networks

This paper considers the problem of selecting either routes that consist of long hops or routes that consist of short hops in a network of multiple-antenna nodes, where each transmitting node employs spatial multiplexing. This distance-dependent route-selection problem is approached from the viewpoint of energy efficiency, where a route is selected with the objective of minimizing the transmission energy consumed while satisfying a target outage criterion at the final destination. Deterministic line networks and 2-D random networks are considered. It is shown that short-hop routing requires less energy than long-hop routing when (1) the number of hops traversed between the source and destination grows large, (2) the target success probability approaches one, or (3) the number of transmit and/or receive antennas grows large. It is also shown that if both routing strategies are subject to the same delay constraint, long-hop routing requires less energy than short-hop routing as the target success probability approaches one. In addition, a numerical analysis indicates that, given loose outage constraints, only a small number of transmit antennas are needed for short-hop routing to have its maximum advantage over long-hop routing, while given stringent outage constraints, the advantage of short-hop over long-hop routing always increases with additional transmit antennas.
CSO and CARMA Observations of L1157. II. Chemical Complexity in the Shocked Outflow

L1157, a molecular dark cloud with an embedded Class 0 protostar possessing a bipolar outflow, is an excellent source for studying shock chemistry, including grain-surface chemistry prior to shocks, and post-shock, gas-phase processing. The L1157-B1 and B2 positions experienced shocks at an estimated ~2000 and 4000 years ago, respectively. Prior to these shock events, temperatures were too low for most complex organic molecules to undergo thermal desorption. Thus, the shocks should have liberated these molecules from the ice grain-surfaces en masse, evidenced by prior observations of SiO and multiple grain mantle species commonly associated with shocks. Grain species, such as OCS, CH_3OH, and HNCO, all peak at different positions relative to species that are preferably formed in higher-velocity shocks or repeatedly shocked material, such as SiO and HCN. Here, we present high spatial resolution (~3") maps of CH_3OH, HNCO, HCN, and HCO^+ in the southern portion of the outflow containing B1 and B2, as observed with Combined Array for Research in Millimeter-Wave Astronomy. The HNCO maps are the first interferometric observations of this species in L1157. The maps show distinct differences in the chemistry within the various shocked regions in L1157B. This is further supported through constraints of the molecular abundances using the non-LTE code radex. We find that the east/west chemical differentiation in C2 may be explained by the contrast of the shock's interaction with either cold, pristine material or warm, previously shocked gas, as seen in enhanced HCN abundances. In addition, the enhancement of the HNCO abundance toward the the older shock, B2, suggests the importance of high-temperature O-chemistry in shocked regions.
The Low-Energy TQFT of the Generalized Double Semion Model

The generalized double semion (GDS) model, introduced by Freedman and Hastings, is a lattice system similar to the toric code, with a gapped Hamiltonian whose definition depends on a triangulation of the ambient manifold M, but whose space of ground states does not depend on the triangulation, but only on the underlying manifold. In this paper, we use topological quantum field theory (TQFT) to investigate the low-energy limit of the GDS model. We define and study a functorial TQFT $$Z_{\mathrm {GDS}}$$ in every dimension n such that for every closed $$(n-1)$$-manifold M, $$Z_{\mathrm {GDS}}(M)$$ is isomorphic to the space of ground states of the GDS model on M; the isomorphism can be chosen to intertwine the actions of the mapping class group of M that arise on both sides. Throughout this paper, we compare our constructions and results with their known analogues for the toric code.
From Solar Cells to Ocean Buoys: Wide-Bandwidth Limits to Absorption by Metaparticle Arrays

The $Y\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}b\phantom{\rule{0}{0ex}}l\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}v\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}c\phantom{\rule{0}{0ex}}h$ $l\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}m\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}t$ has long provided an upper bound for how much enhancement can be achieved through surface texturing in solar cells. In this study, the authors develop a similar approximate limit for dilute arrays of absorbing ``metaparticles'', and interestingly apply the result to arrays of buoys for harvesting the energy of oceanic waves. This result is applicable to a broad range of scattering problems; in particular it bridges the gap between two seemingly different problems in energy extraction that nonetheless feature similar underlying physics.
USING ForeCAT DEFLECTIONS AND ROTATIONS TO CONSTRAIN THE EARLY EVOLUTION OF CMEs

To accurately predict the space weather effects of the impacts of coronal mass ejection (CME) at Earth one must know if and when a CME will impact Earth and the CME parameters upon impact. In 2015 Kay et al. presented Forecasting a CME's Altered Trajectory (ForeCAT), a model for CME deflections based on the magnetic forces from the background solar magnetic field. Knowing the deflection and rotation of a CME enables prediction of Earth impacts and the orientation of the CME upon impact. We first reconstruct the positions of the 2010 April 8 and the 2012 July 12 CMEs from the observations. The first of these CMEs exhibits significant deflection and rotation (34° deflection and 58° rotation), while the second shows almost no deflection or rotation (<3° each). Using ForeCAT, we explore a range of initial parameters, such as the CME's location and size, and find parameters that can successfully reproduce the behavior for each CME. Additionally, since the deflection depends strongly on the behavior of a CME in the low corona, we are able to constrain the expansion and propagation of these CMEs in the low corona.
Nonlocal gravity in the solar system

The implications of the recent classical nonlocal generalization of Einstein's theory of gravitation for gravitational physics in the solar system are investigated. In this theory, the nonlocal character of gravity appears to simulate dark matter. Nonlocal gravity in the Newtonian regime involves a reciprocal kernel with three spatial parameters, of which two have already been determined from the rotation curves of spiral galaxies and the internal dynamics of clusters of galaxies. However, the short-range parameter a 0 remains to be determined. In this connection, the nonlocal contribution to the perihelion precession of a planetary orbit is estimated and a preliminary lower limit on a 0 is determined.
FAR-ULTRAVIOLET OBSERVATIONS OF COMET C/2012 S1 (ISON) FROM FORTIS

We have used the unique far-UV imaging capability offered by a sounding-rocket-borne instrument to acquire observations of C/2012 S1 (ISON) when its angular separation with respect to the Sun was 26 deg.3 on 2013 November 20.49. At the time of observation, the comet's heliocentric distance and velocity relative to the Sun were r h = 0.43 au and r (sub h) = 62.7 km s)exp. -1). Images dominated by C Iota Lambda 1657 and H Iota Lambda 1216 were acquired over a 10(exp. 6) x 10(exp. 6) km(exp. 2) region. The water production rate implied by the Ly Alpha observations is constrained to be Q H2O is much greater than 8 x 10(exp. 29) s(exp. -1) while the neutral carbon production rate was Q(sub c) is much greater than 4 x 10(exp. 28) s(exp. -1). The radial profile of C I was consistent with it being a dissociation product of a parent molecule with a lifetime T is approx. 5 x 10(exp. 4) s, favoring a parent other than CO. We constrain the Q(sub co) production rate to 5(+1.5)(-7.5), 10(exp. 28) s(exp. -1) with 1 sigma errors derived from photon statistics. The upper limit on the Q (sub CO)/Q(sub H2O) is 6%.
Hot little string correlators: a view from supergravity

We study the propagation of a massless minimally coupled scalar in the near horizon geometry of non-extremal NS5-branes. Using the holographic principle for dilatonic backgrounds we compute the two-point function of an operator in Little String Theory at the Hagedorn temperature. We then comment on relations with correlation functions in two dimensional string theory.
Strong hypercontractivity and logarithmic Sobolev inequalities on stratified complex Lie groups

We show that for a hypoelliptic Dirichlet form operator A on a stratified complex Lie group, if the logarithmic Sobolev inequality holds, then a holomorphic projection of A is strongly hypercontractive in the sense of Janson. This extends previous results of Gross to a setting in which the operator A is not holomorphic.
SUPPRESSING SUPER-HORIZON CURVATURE PERTURBATIONS?

We consider the possibility of suppressing super-horizon curvature perturbations after the end of the ordinary slow-roll inflationary stage. This is the opposite of the curvaton limit. We assume that large curvature perturbations are created by the inflaton and investigate if they can be diluted or suppressed by a second very homogeneous field which starts to dominate the energy density of the universe shortly after the end of inflation. We show explicit that the gravitational sourcing of inhomogeneities from the more inhomogeneous fluid to the more homogeneous fluid makes the suppression difficult if not impossible to achieve.
Elastic Cheerios effect: Self-assembly of cylinders on a soft solid

A rigid cylinder placed on a soft gel deforms its surface. When multiple cylinders are placed on the surface, they interact with each other via the topography of the deformed gel which serves as an energy landscape; as they move, the landscape changes which in turn changes their interaction. We use a combination of experiments, simple scaling estimates and numerical simulations to study the self-assembly of cylinders in this elastic analog of the "Cheerios Effect", which describes capillary interactions on a fluid interface. Our results show that the effective two-body interaction can be well described by an exponential attraction potential as a result of which the dynamics also show an exponential behavior with respect to the separation distance. When many cylinders are placed on the gel, the cylinders cluster together if they are not too far apart; otherwise their motion gets elastically arrested.
Bayesian Attitude Estimation With the Matrix Fisher Distribution on SO(3)

This paper focuses on a stochastic formulation of Bayesian attitude estimation on the special orthogonal group. In particular, an exponential probability density model for random matrices, referred to as the matrix Fisher distribution, is utilized to represent the uncertainties of attitude estimates and measurements in a global fashion. Various stochastic properties of the matrix Fisher distribution are derived on the special orthogonal group, and based on these, two types of intrinsic frameworks for Bayesian attitude estimation are constructed. These avoid complexities or singularities of the attitude estimators developed in terms of quaternions. The proposed approaches are particularly useful to deal with large estimation errors or large uncertainties for complex attitude maneuvers.
Fractional Dehn twists in knot theory and contact topology

Fractional Dehn twists give a measure of the difference between the relative isotopy class of a homeomorphism of a bordered surface and the Thurston representative of its free isotopy class. We show how to estimate and compute these invariants. We discuss the relationship of our work to stabilization problems in classical knot theory, general open book decompositions and contact topology. We include an elementary characterization of overtwistedness for contact structures described by open book decompositions.
An operational definition of quark and gluon jets

While “quark” and “gluon” jets are often treated as separate, well-defined objects in both theoretical and experimental contexts, no precise, practical, and hadron-level definition of jet flavor presently exists. To remedy this issue, we develop and advocate for a data-driven, operational definition of quark and gluon jets that is readily applicable at colliders. Rather than specifying a per-jet flavor label, we aggregately define quark and gluon jets at the distribution level in terms of measured hadronic cross sections. Intuitively, quark and gluon jets emerge as the two maximally separable categories within two jet samples in data. Benefiting from recent work on data-driven classifiers and topic modeling for jets, we show that the practical tools needed to implement our definition already exist for experimental applications. As an informative example, we demonstrate the power of our operational definition using Z+jet and dijet samples, illustrating that pure quark and gluon distributions and fractions can be successfully extracted in a fully well-defined manner.
The $5$–local homotopy of $eo_4$

The element r is primitive. The origin of the formulas for the right units and coproduct on r is geometric. The Hopf algebroid .A; / corepresents curves of the form (1) y 1 D xC a1x C a2x C C ap; together with coordinate transformations x 7! xC r (we recover the grading if we further consider a scaling action .x;y/ 7! . p x; y/). The coefficients ai can then be interpreted as functions on the moduli stack of all such curves. The elements of A that are invariant under translation are the analogue of modular forms in this context, and one of the goals of this paper is to compute the full ring of invariants for this Hopf algebroid using the full cohomology ring.
Generalized ABC theorems for non-Archimedean entire functions of several variables in arbitrary characteristic

We prove generalized ABC theorems for vanishing sums of non-Archimedean entire functions of several variables in arbitrary characteristic.
An alternative approach to extending pseudo-Anosovs over compression bodies

Biringer, Johnson, and Minsky proved that any pseudo-Anosov whose stable lamination is the limit of disks in a compression body has a power which extends over some non-trivial minimal compression body. This paper presents an alternative proof of their theorem. The key ingredient is the existence of a certain collection of disks whose boundaries are formed from an arc of the stable lamination and an arc of the unstable lamination. The proof here also shows that there are only finitely many minimal compression bodies over which a power of a pseudo-Anosov can extend. 57M99
von-Neumann stability and singularity resolution in loop quantized Schwarzschild black hole

Though loop quantization of several spacetimes has exhibited existence of a bounce via an explicit evolution of states using numerical simulations, the question about the way central singularity is resolved in the black hole interior has remained open. The quantum Hamiltonian constraint in loop quantization turns out to be a finite difference equation whose stability is important to understand to gain insights on the viability of the underlying quantization and resulting physical implications. We take first steps towards addressing these issues for a loop quantization of the Schwarzschild interior recently given by Corichi and Singh. Von-Neumann stability analysis is performed using separability of solutions as well as a full two dimensional quantum difference equation. This results in a stability condition for black holes which have a very large mass compared to the Planck mass. For black holes of smaller masses evidence of numerical instability is found. In addition, stability analysis for macroscopic black holes leads to a constraint on the choice of the allowed states in numerical evolution. With the caveat of using kinematical norm, sharply peaked Gaussian states are evolved using the quantum difference equation and singularity resolution is obtained. A bounce is found for one of the triad variables, but for the other triad variable singularity resolution amounts to a non-singular passage through the zero volume. States are found to be peaked at the classical trajectory for a long time before and after the singularity resolution, and retain their semi-classical character across the zero volume. Our main result is that quantum bounce occurs in loop quantized Schwarzschild interior at least for macroscopic black holes.
Tension is dimension

We propose a simple universal formula for the tension of a D-brane in terms of a regularized dimension of the associated conformal field theory statespace.
POST-CAPTURE EVOLUTION OF POTENTIALLY HABITABLE EXOMOONS

The satellites of extrasolar planets (exomoons) have been recently proposed as astrobiological targets. Since giant planets in the habitable zone are thought to have migrated there, it is possible that they may have captured a former terrestrial planet or planetesimal. We therefore attempt to model the dynamical evolution of a terrestrial planet captured into orbit around a giant planet in the habitable zone of a star. We find that approximately half of loose elliptical orbits result in stable circular orbits over timescales of less than a few million years. We also find that those orbits are mostly at low inclination, but have no prograde/retrograde preference. In addition, we calculate the transit timing and duration variations for the resulting systems, and find that potentially habitable Earth-mass exomoons should be detectable.
Stability of three-fermion clusters with finite range of attraction

Three quantum particles with on-site repulsion and nearest-neighbour attraction on a one-dimensional lattice are considered. The three-body Schr?dinger equation is reduced to a set of single-variable integral equations. Energies of three-particle bound complexes (trions) are found from self-consistency of the approximating matrix equation. In the case of spin- fermions, the ground-state trion energy, the excited-state energies, the trion spectra and stability regions are obtained for total spins S?=?1/2 and S?=?3/2. In the S?=?1/2 sector, a narrow but finite parameter region is identified where the ground state consists of a stable fermion pair and an unbound fermion. Also presented is the reference case of spin-0 bosons.
New estimates of Hilbert–Kunz multiplicities for local rings of fixed dimension

We present results on the Watanabe–Yoshida conjecture for the Hilbert–Kunz multiplicity of a local ring of positive characteristic. By improving on a “volume estimate” giving a lower bound for Hilbert–Kunz multiplicity, we obtain the conjecture when the ring has either Hilbert–Samuel multiplicity less than or equal to 5 or dimension less than or equal to 6. For nonregular rings with fixed dimension, a new lower bound for the Hilbert–Kunz multiplicity is obtained.
V2492 Cygni: The Early Evolution of the 2010 Outburst

We present Gemini-North optical and near-IR observations of a young eruptive star in Cygnus, designated as V2492 Cygni in the General Catalog of Variable Stars. This object is one of two young stars, located within 2 deg of each other, that recently brightened by around 5 mag and were reported as possible new FU Orionis-type variables. The outburst spectrum of V2492 Cygni shows atomic emission features throughout the optical and near-infrared. In the optical, Hα is in emission and has an associated blueshifted absorption component. The far-red Ca II triplet lines are also in emission and, as with Hα, possess significant blueshifted absorption. The optical TiO molecular bands are also in emission. In the near-infrared, Paβ, Brγ, and the CO overtone bandheads are strongly in emission. Such spectral characteristics are very similar to those exhibited by both EX Lupi, the progenitor of the EXor class of eruptive variables, during its 2008 extreme outburst, and V1647 Ori during its elevated phase in 2003. Additionally, we consider archival data on V2492 Cygni and investigate the pre-outburst nature of this young star. We construct a quiescent-phase spectral energy distribution which, via model fitting, gives insight into the circumstellar environment of the object prior to the current eruption. Our investigation strongly suggests that the V2492 Cygni outburst appears to be more consistent with an EXor event, a fact supported by its recent 2 mag fading and stochastic variability.
COLLISIONAL EXCITATION OF FAR-INFRARED LINE EMISSIONS FROM WARM INTERSTELLAR CARBON MONOXIDE (CO)

Motivated by recent observations with Herschel/PACS, and the availability of new rate coefficients for the collisional excitation of CO, the excitation of warm astrophysical CO is revisited with the use of numerical and analytic methods. For the case of an isothermal medium, results have been obtained for a wide range of gas temperatures (100-5000 K) and H2 densities (103-109 cm–3), and presented in the form of rotational diagrams, in which the logarithm of the column density per magnetic substate, log (NJ /gJ ), is plotted for each state, as a function of its energy, EJ . For rotational transitions in the wavelength range accessible to Herschel/PACS, such diagrams are nearly linear when n(H2) ≥ 108 cm–3. When n(H2) ~ 106.8-108 cm–3, they exhibit significant negative curvature, whereas when n(H2) ≤ 104.8 cm–3, the curvature is uniformly positive throughout the PACS-accessible range. Thus, the observation of a positively curved CO rotational diagram does not necessarily require the presence of multiple temperature components. Indeed, for some sources observed with Herschel/PACS, the CO rotational diagrams show a modest positive curvature that can be explained by a single isothermal component. Typically, the required physical parameters are densities in the 104-105 cm–3 range and temperatures close to the maximum at which CO can survive. Other sources exhibit rotational diagrams with more curvature than can be accounted for by a single temperature component. For the case of a medium with a power-law distribution of gas temperatures, dN/dT∝T –b , results have been obtained for H2 densities 103-109 cm–3 and power-law indices, b, in the range 1-5; such a medium can account for a CO rotational diagram that is more positively curved than any resulting from an isothermal medium.
THE SPACE WEATHER OF PROXIMA CENTAURI b

A planet orbiting in the "habitable zone" of our closest neighboring star, Proxima Centauri, has recently been discovered, and the next natural question is whether or not Proxima b is "habitable." Stellar winds are likely a source of atmospheric erosion that could be particularly severe in the case of M dwarf habitable zone planets that reside close to their parent star. Here, we study the stellar wind conditions that Proxima b experiences over its orbit. We construct 3D MHD models of the wind and magnetic field around Proxima Centauri using a surface magnetic field map for a star of the same spectral type and scaled to match the observed ~600 G surface magnetic field strength of Proxima. We examine the wind conditions and dynamic pressure over different plausible orbits that sample the constrained parameters of the orbit of Proxima b. For all the parameter space explored, the planet is subject to stellar wind pressures of more than 2000 times those experienced by Earth from the solar wind. During an orbit, Proxima b is also subject to pressure changes of 1–3 orders of magnitude on timescales of a day. Its magnetopause standoff distance consequently undergoes sudden and periodic changes by a factor of 2–5. Proxima b will traverse the interplanetary current sheet twice each orbit, and likely crosses into regions of subsonic wind quite frequently. These effects should be taken into account in any physically realistic assessment or prediction of its atmospheric reservoir, characteristics, and loss.
Probing small-x gluons by low-mass Drell-Yan pairs at RHIC and LHC

We calculate the transverse momentum distribution of low-mass Drell-Yan pairs in QCD perturbation theory with all-order resummation. We demonstrate that the transverse momentum distribution of low-mass Drell-Yan pairs is an advantageous source of constraints on the gluon distribution and its nuclear dependence. With the reduction in background, we argue that low-mass Drell-Yan pairs in the forward region provide a good and clean probe of small-x gluons at RHIC and LHC.
Potential Variations in the Interstellar N I Abundance

We present Far Ultraviolet Spectroscopic Explorer (FUSE) and Space Telescope Imaging Spectrograph observations of the weak interstellar N I λ1160 doublet toward 17 high-density sight lines [N(Htot) ≥ 1021 cm-2]. When combined with published data, our results reveal variations in the fractional N I abundance showing a systematic deficiency at large N(Htot). At the FUSE resolution (~20 km s-1), the effects of unresolved saturation cannot be conclusively ruled out, although O I λ1356 shows little evidence of saturation. We investigated the possibility that the N I variability is due to the formation of N2 in our mostly dense regions. The 0-0 band of the c 1Σ-X 1Σ transition of N2 at 958 A should be easily detected in our FUSE data; for 10 of the denser sight lines, N2 is not observed at a sensitivity level of a few times 1014 cm-2. The observed N I variations are suggestive of an incomplete understanding of nitrogen chemistry.
Tetraplectic structures, tri-momentum maps, and quaternionic flag manifolds

Abstract The purpose of this note is to define tri-momentum maps for certain manifolds with an Sp(1)n-action. We exhibit many interesting examples of such spaces using quaternions. We show how these maps can be used to reduce such manifolds to ones with fewer symmetries. The images of such maps for quaternionic flag manifolds, which are defined using the Dieudonne determinant, resemble the polytopes from the complex case.
The error term in the Sato–Tate conjecture

Let $${f(z) = \sum_{n=1}^\infty a(n)e^{2\pi i nz} \in S_k^{\mathrm{new}}(\Gamma_0(N))}$$ be a newform of even weight $${k \geq 2}$$ that does not have complex multiplication. Then $${a(n) \in \mathbb{R}}$$ for all n; so for any prime p, there exists $${\theta_p \in [0, \pi]}$$ such that $${a(p) = 2p^{(k-1)/2} {\rm cos} (\theta_p)}$$ . Let $${\pi(x) = \#\{p \leq x\}}$$ . For a given subinterval $${[\alpha, \beta]\subset[0, \pi]}$$ , the now-proven Sato–Tate conjecture tells us that as $${x \to \infty}$$ , $$ \#\{p \leq x: \theta_p \in I\} \sim \mu_{ST} ([\alpha, \beta])\pi(x),\quad \mu_{ST} ([\alpha, \beta]) = \int\limits_{\alpha}^\beta \frac{2}{\pi}{\rm sin}^2(\theta) d\theta. $$ Let $${\epsilon > 0}$$ . Assuming that the symmetric power L-functions of f are automorphic, we prove that as $${x \to \infty}$$ , $$ \#\{p \leq x: \theta_p \in I\} = \mu_{ST} ([\alpha, \beta])\pi(x) + O\left(\frac{x}{(\log x)^{9/8-\epsilon}} \right), $$ where the implied constant is effectively computable and depends only on k,N, and $${\epsilon}$$ .
THE HEISENBERG–EULER EFFECTIVE ACTION: 75 YEARS ON

On this 75th anniversary of the publication of the Heisenberg–Euler paper on the full nonperturbative one-loop effective action for quantum electrodynamics I review their paper and discuss some of the impacts it has had on quantum field theory.
3–manifold invariants and periodicity of homology spheres

We show how the periodicity of a homology sphere is reflected in the Reshetikhin-Turaev-Witten invariants of the manifold. These yield a criterion for the periodicity of a homology sphere.
Detection of Additional Be+sdO Systems from IUE Spectroscopy

There is growing evidence that some Be stars were spun up through mass transfer in a close binary system, leaving the former mass donor star as a hot, stripped-down object. There are five known cases of Be stars with hot subdwarf (sdO) companions that were discovered through International Ultraviolet Explorer (IUE) spectroscopy. Here we expand the search for Be+sdO candidates using archival FUV spectra from IUE. We collected IUE spectra for 264 stars and formed cross-correlation functions (CCFs) with a model spectrum for a hot subdwarf. Twelve new candidate Be+sdO systems were found, and eight of these display radial velocity variations associated with orbital motion. The new plus known Be+sdO systems have Be stars with spectral subtypes of B0 to B3, and the lack of later-type systems is surprising given the large number of cooler B-stars in our sample. We discuss explanations for the observed number and spectral type distribution of the Be+sdO systems, and we argue that there are probably many Be systems with stripped companions that are too faint for detection through our analysis.
Protoplanetary Disk Resonances and Type I Migration

Waves reflected by the inner edge of a protoplanetary disk are shown to significantly modify Type I migration, even allowing the trapping of planets near the inner disk edge for small planets in a range of disk parameters. This may inform the distribution of planets close to their central stars, as observed recently by the Kepler mission.
Extension of modularity density for overlapping community structure

Modularity is widely used to effectively measure the strength of the disjoint community structure found by community detection algorithms. Although several overlapping extensions of modularity were proposed to measure the quality of overlapping community structure, there is lack of systematic comparison of different extensions. To fill this gap, we overview overlapping extensions of modularity to select the best. In addition, we extend the Modularity Density metric to enable its usage for overlapping communities. The experimental results on four real networks using overlapping extensions of modularity, overlapping modularity density, and six other community quality metrics show that the best results are obtained when the product of the belonging coefficients of two nodes is used as the belonging function. Moreover, our experiments indicate that overlapping modularity density is a better measure of the quality of overlapping community structure than other metrics considered.
A Proposal for Loop-Transformation Pragmas

Pragmas for loop transformations, such as unrolling, are implemented in most mainstream compilers. They are used by application programmers because of their ease of use compared to directly modifying the source code of the relevant loops. We propose additional pragmas for common loop transformations that go far beyond the transformations today’s compilers provide and should make most source rewriting for the sake of loop optimization unnecessary. To encourage compilers to implement these pragmas, and to avoid a diversity of incompatible syntaxes, we would like to spark a discussion about an inclusion to the OpenMP standard.
Design and test of 704 MHz and 2.1 GHz normal conducting cavities for low energy RHIC electron cooler

The low energy RHIC electron cooler (LEReC) is currently under commissioning at BNL to improve RHIC luminosity for heavy ion beam energies below $10\text{ }\text{ }\mathrm{GeV}/\mathrm{nucleon}$. The linac of LEReC consists of a dc photoemission gun, one 704 MHz superconducting radio frequency booster cavity, and three normal conducting cavities. It is designed to deliver a 1.6--2.6 MeV electron beam, with peak-to-peak momentum spread $dp/p$ of less than $\ifmmode\pm\else\textpm\fi{}7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}4}$. Two of the three normal conducting cavities will be used in LEReC for energy spread correction: a single-cell 704 MHz cavity for energy dechirping and a three-cell 2.1 GHz third harmonic cavity for rf curvature correction. In this paper, we present the designs and rf test results of these two cavities.
Nonperturbative tests of the parent/orbifold correspondence in supersymmetric gauge theories

It has been shown that a procedure analogous to orbifolding in string theory, when applied to certain large-N field theories, leaves correlators invariant perturbatively. We test nonperturbative agreement of some aspects of the parent and orbifold theories. More specifically, we find that the holomorphic gauge couplings on the Coulomb branch in the parent and orbifold Seiberg-Witten theories are related, even away from the 't Hooft limit. We also check that any large-N theory which has an infrared conformal fixed point and satisfies certain anomaly positivity constraints required by such theories will continue to satisfy those constraints after orbifolding. We discuss extensions of these results to finite N.
GMRES-accelerated ADMM for quadratic objectives

We consider the sequence acceleration problem for the alternating direction method of multipliers (ADMM) applied to a class of equality-constrained problems with strongly convex quadratic objectives, which frequently arise as the Newton subproblem of interior-point methods. Within this context, the ADMM update equations are linear, the iterates are confined within a Krylov subspace, and the general minimum residual (GMRES) algorithm is optimal in its ability to accelerate convergence. The basic ADMM method solves a $\kappa$-conditioned problem in $O(\sqrt{\kappa})$ iterations. We give theoretical justification and numerical evidence that the GMRES-accelerated variant consistently solves the same problem in $O(\kappa^{1/4})$ iterations for an order-of-magnitude reduction in iterations, despite a worst-case bound of $O(\sqrt{\kappa})$ iterations. The method is shown to be competitive against standard preconditioned Krylov subspace methods for saddle-point problems. The method is embedded within SeDuMi, a po...
COOLING, AGN FEEDBACK, AND STAR FORMATION IN SIMULATED COOL-CORE GALAXY CLUSTERS

Numerical simulations of active galactic nuclei (AGN) feedback in cool-core galaxy clusters have successfully avoided classical cooling flows, but often produce too much cold gas. We perform adaptive mesh simulations that include momentum-driven AGN feedback, self-gravity, star formation and stellar feedback, focusing on the interplay between cooling, AGN heating and star formation in an isolated cool-core cluster. Cold clumps triggered by AGN jets and turbulence form filamentary structures tens of kpc long. This cold gas feeds both star formation and the supermassive black hole (SMBH), triggering an AGN outburst that increases the entropy of the ICM and reduces its cooling rate. Within 1-2 Gyr, star formation completely consumes the cold gas, leading to a brief shutoff of the AGN. The ICM quickly cools and redevelops multiphase gas, followed by another cycle of star formation/AGN outburst. Within 6.5 Gyr, we observe three such cycles. There is good agreement between our simulated cluster and the observations of cool-core clusters. ICM cooling is dynamically balanced by AGN heating, and a cool-core appearance is preserved. The minimum cooling time to free-fall time ratio typically varies between a few and $\gtrsim 20$. The star formation rate (SFR) covers a wide range, from 0 to a few hundred $\rm M_{\odot}\, yr^{-1}$, with an average of $\sim 40 \,\rm M_{\odot}\, yr^{-1}$. The instantaneous SMBH accretion rate shows large variations on short timescales, but the average value correlates well with the SFR. Simulations without stellar feedback or self-gravity produce qualitatively similar results, but a lower SMBH feedback efficiency (0.1% compared to 1%) results in too many stars.
Six indications of radical new physics in supernovae Ia

After more than 40 years since the basic standard model for supernovae Ia (SN Ia) was proposed, many astronomers are still hopeful that this phenomenon will ultimately be understood in terms of Newtonian gravity plus nuclear and particle physics as they existed in the 1930s. In spite of this fact, there are at least six nagging puzzles in supernovae physics that suggest some radical new physics input may be necessary. “Radical” in this context means a physics idea that did not exist in the 1930s and that is still not experimentally confirmed in 2017.
Be More with Less: Hypergraph Attention Networks for Inductive Text Classification

Text classification is a critical research topic with broad applications in natural language processing. Recently, graph neural networks (GNNs) have received increasing attention in the research community and demonstrated their promising results on this canonical task. Despite the success, their performance could be largely jeopardized in practice since they are: (1) unable to capture high-order interaction between words; (2) inefficient to handle large datasets and new documents. To address those issues, in this paper, we propose a principled model -- hypergraph attention networks (HyperGAT), which can obtain more expressive power with less computational consumption for text representation learning. Extensive experiments on various benchmark datasets demonstrate the efficacy of the proposed approach on the text classification task.
Generation of a North/South Magnetic Field Component from Variations in the Photospheric Magnetic Field

We address the problem of calculating the transverse magnetic field in the solar wind outside of the hypothetical sphere that is called the source surface where the solar wind originates. This calculation must overcome a widely used fundamental assumption about the source surface – the field is normally required to be purely radial at the source surface. Our model rests on the fact that a change in the radial field strength at the source surface is a change in the field line density. Surrounding field lines must move laterally to accommodate this field line density change. As the outward wind velocity drags field lines past the source surface, this lateral component of motion produces a tilt, implying there is a transverse component to the field. An analytic method of calculating the lateral translation speed of the field lines is developed. We apply the technique to an interval of approximately two Carrington rotations at the beginning of 2011 using 2-h averages of data from the Helioseismic Magnetic Imager instrument onboard the Solar Dynamics Observatory spacecraft. We find that the value of the transverse magnetic field is dominated on a global scale by the effects of high-latitude concentrations of field lines that are buffeted by supergranular motions.
Modular curves of prime-power level with infinitely many rational points

For each open subgroup G of GL2(ℤ ) containing − I with full determinant, let XG∕ℚ denote the modular curve that loosely parametrizes elliptic curves whose Galois representation, which arises from the Galois action on its torsion points, has image contained in G. Up to conjugacy, we determine a complete list of the 248 such groups G of prime power level for which XG(ℚ) is infinite. For each G, we also construct explicit maps from each XG to the j-line. This list consists of 220 modular curves of genus 0 and 28 modular curves of genus 1. For each prime l, these results provide an explicit classification of the possible images of l-adic Galois representations arising from elliptic curves over ℚ that is complete except for a finite set of exceptional j-invariants.
Coupled orbiting inertial reference systems and Geopotential Research Mission (GRM) geodesy

Two spacecraft, one following the other with a separation of a few hundred kilometers and orbiting at an altitude of 160 km in a 90-degree polar orbit, are used to detect the minute variations in the earth's gravitational field. Housed in a capacitive cavity located at the centroid of the spacecraft is a free-floating metallic spherical proof-mass, which is the sensor controlling the thrusters that nullify all nongravitational forces on the spacecraft. The proof-mass in each spacecraft is the inertial-guidance reference for its host spacecraft, and the proof-masses are coupled together by a millimeter-wave link. This coupled system detects minute changes in the spacecraft's orbital positions and thus measures the anomalies present in the gravitational field of the earth. To derive a global geodetic model of the gravitational field with an amplitude resolution of 1 milligal and a spatial resolution of 100 km requires that the relative velocity between the proof-mass references be determined to within 1 micron/s.
NSGANetV2: Evolutionary Multi-objective Surrogate-Assisted Neural Architecture Search

In this paper, we propose an efficient NAS algorithm for generating task-specific models that are competitive under multiple competing objectives. It comprises of two surrogates, one at the architecture level to improve sample efficiency and one at the weights level, through a supernet, to improve gradient descent training efficiency. On standard benchmark datasets (C10, C100, ImageNet), the resulting models, dubbed NSGANetV2, either match or outperform models from existing approaches with the search being orders of magnitude more sample efficient. Furthermore, we demonstrate the effectiveness and versatility of the proposed method on six diverse non-standard datasets, e.g. STL-10, Flowers102, Oxford Pets, FGVC Aircrafts etc. In all cases, NSGANetV2s improve the state-of-the-art (under mobile setting), suggesting that NAS can be a viable alternative to conventional transfer learning approaches in handling diverse scenarios such as small-scale or fine-grained datasets. Code is available at https://github.com/mikelzc1990/nsganetv2.
Conjecture $\mathcal{O}$ holds for some horospherical varieties of Picard rank 1

Property 𝒪 for an arbitrary complex, Fano manifold X is a statement about the eigenvalues of the linear operator obtained from the quantum multiplication of the anticanonical class of X. Conjecture 𝒪 is a conjecture that property 𝒪 holds for any Fano variety. Pasquier classified the smooth nonhomogeneous horospherical varieties of Picard rank 1 into five classes. Conjecture 𝒪 has already been shown to hold for the odd symplectic Grassmannians, which is one of these classes. We will show that conjecture 𝒪 holds for two more classes and an example in a third class of Pasquier’s list. Perron–Frobenius theory reduces our proofs to be graph-theoretic in nature.
Impact of a course transformation on students’ reasoning about measurement uncertainty

Even traditional physics lab courses can create opportunities for students to learn important aspects of conceptual physics and to develop expert physics practices.
The wide-field infrared transient explorer (WINTER)

The Wide-Field Infrared Transient Explorer (WINTER) is a new infrared time-domain survey instrument which will be deployed on a dedicated 1 meter robotic telescope at the Palomar Observatory. WINTER will perform a seeing-limited time domain survey of the infrared (IR) sky, with a particular emphasis on identifying r -process material in binary neutron star (BNS) merger remnants detected by LIGO. We describe the scientific goals and survey design of the WINTER instrument. With a dedicated trigger and the ability to map the full LIGO O4 positional error contour in the IR to a distance of 190 Mpc within four hours, WINTER will be a powerful kilonova discovery engine and tool for multi-messenger astrophysics investigations. In addition to follow-up observations of merging binaries, WINTER will facilitate a wide range of time-domain astronomical observations, all the while building up a deep coadded image of the static infrared sky suitable for survey science. WINTER’s custom camera features six commercial large-format Indium Gallium Arsenide (InGaAs) sensors and a tiled optical system which covers a <1-square-degree field of view with 90% fill factor. The instrument observes in Y, J and a short-H (Hs) band tuned to the long-wave cutoff of the InGaAs sensors, covering a wavelength range from 0.9 – 1.7 microns. We present the design of the WINTER instrument and current progress towards final integration at the Palomar Observatory and commissioning planned for mid-2021.
Necessity of hyperbolic absolute risk aversion for the concavity of consumption functions

Abstract Carroll and Kimball (1996) have shown that, in the class of utility functions that are strictly increasing, strictly concave, and have nonnegative third derivatives, hyperbolic absolute risk aversion (HARA) is sufficient for the concavity of consumption functions in general consumption-saving problems. This paper shows that HARA is necessary, implying the concavity of consumption is not a robust prediction outside the HARA class.
Competitive Equilibrium and Trading Networks: A Network Flow Approach

This paper considers a network of agents who trade indivisible goods or services via bilateral contracts. Under a substitutability assumption on preferences, it is known that a competitive equilibr...
Accounting standards and debt covenants: Has the “balance sheet approach” led to a decline in the use of balance sheet covenants?

Abstract Recent years have seen a sharp decline in the use of balance sheet-based covenants in private debt contracts. I hypothesize that changes in accounting standards can explain part of this decline. Standard setting has shifted towards a “balance sheet approach”, which I predict has made the balance sheet less useful for contracting. I measure the effect of the balance sheet approach on specific borrowers using a volatility ratio. I find that borrowers with greater volatility ratios are less likely to have balance sheet-based covenants. This evidence is consistent with reductions in the contracting usefulness of the balance sheet being associated with reductions in balance sheet covenants.
Earnings Management Around Debt-Covenant Violations – An Empirical Investigation Using a Large Sample of Quarterly Data

I find that managers manage earnings upward in the quarters preceding a debt-covenant violation, but downward in the quarter a violation occurs. And they continue to manage earnings downward while the firm remains in violation. Because this scenario can play out within a year, the use of yearly data to examine the debt-covenant hypothesis can be problematic. Further analysis shows that the earnings management around the debt-covenant violation is also done to improve the manager�s bargaining power in the renegotiation that follows the violation. Furthermore, I find no evidence of excessive earnings management by high-debt firms to stave off a violation, but I do find evidence that the Sarbanes�Oxley Act restrains managers from using accruals to stave off a violation. These results are based on examining 193,803 firm-quarters, 8,804 firms, and 2,035 new covenant violations spanning 1996 to 2007.
Debt maturity across firm types: Evidence from a major developing economy

Abstract Existing literature provides little guidance on whether various debt maturity theories are useful in understanding the debt maturity choices of firms that are privately-held, small, and/or outside the manufacturing industry in developing economies. This paper conducts a comparative test of the major debt maturity theories using a firm-level dataset that covers a wide variety of firm types in a major developing economy, Turkey. Our findings provide considerable support for the liquidity risk, agency, and maturity-matching theories. The macroeconomic environment also has an important impact on debt maturity. The evidence for the signaling and tax theories, however, is weak at best.