cssi/SciSciGPT-SciSciNet huggingface dataset:
Cylindrical vector beams for rapid polarization-dependent measurements in atomic systems.

We demonstrate the use of cylindrical vector beams – beams with spatially varying polarization – for detecting and preparing the spin of a warm rubidium vapor in a spatially dependent manner. We show that a modified probe vector beam can serve as an atomic spin analyzer for an optically pumped medium, which spatially modulates absorption of the beam. We also demonstrate space-variant atomic spin by optical pumping with the vector beams. The beams are thus beneficial for making single-shot polarization-dependent measurements, as well as for providing a means of preparing samples with position-dependent spin.
Unveiling Coordinated Groups Behind White Helmets Disinformation

Propaganda, disinformation, manipulation, and polarization are the modern illnesses of a society increasingly dependent on social media as a source of news. In this paper, we explore the disinformation campaign, sponsored by Russia and allies, against the Syria Civil Defense (a.k.a. the White Helmets). We unveil coordinated groups using automatic retweets and content duplication to promote narratives and/or accounts. The results also reveal distinct promoting strategies, ranging from the small groups sharing the exact same text repeatedly, to complex “news website factories” where dozens of accounts synchronously spread the same news from multiple sites.
DISCOVERY OF AN UNUSUALLY BLUE L DWARF WITHIN 10 pc OF THE SUN

We report the discovery of an unusually blue L5 dwarf within 10 pc of the Sun from a search of Sloan Digital Sky Survey (SDSS) spectra. A spectrophotometric distance estimate of 8.0 ± 1.6 pc places SDSS J141624.08+134826.7 among the six closest known L dwarfs. SDSS 1416+13 was overlooked in infrared color-based searches because of its unusually blue J – K S color, which also identifies it as the nearest member of the blue L dwarf subclass. We present additional infrared and optical spectroscopy from the IRTF/SpeX and Magellan/MagE spectrographs and determine UVW motions that indicate thin disk kinematics. The inclusion of SDSS 1416+13 in the 20 pc sample of L dwarfs increases the number of L5 dwarfs by 20% suggesting that the L dwarf luminosity function may be far from complete.
Introduction to dark matter experiments

This is a set of four lectures presented at the Theoretical Advanced Study Institute (TASI-09) in June 2009. I provide an introduction to experiments designed to detect WIMP dark matter directly, focussing on building intuitive understanding of the characteristics of potential WIMP signals and the experimental techniques. After deriving the characteristics of potential signals in direct-detection experiments for standard WIMP models, I summarize the general experimental methods shared by most direct-detection experiments and review the advantages, challenges, and status of such searches (as of late 2009). Experiments are already probing SUSY models, with best limits on the spin-independent coupling below 10−7 pb.
The microscopic origin of DMI in magnetic bilayers and prediction of giant DMI in new bilayers

Skyrmions are widely regarded as promising candidates for emergent spintronic devices. Dzyaloshinskii–Moriya interaction (DMI) is often critical to the generation and manipulation of skyrmions. However, there is a fundamental lack of understanding of the origin of DMI or the mechanism by which DMI generates skyrmions in magnetic bilayers. Very little is known of the material parameters that determine the value of DMI. This knowledge is vital for rational design of skyrmion materials and further development of skyrmion technology. To address this important problem, we investigate DMI in magnetic bilayers using first principles. We present a new theoretical model that explains the microscopic origin of DMI in magnetic bilayers. We demonstrate that DMI depends on two parameters, interfacial hybridization and orbital contributions of the heavy metal. Using these parameters, we explain the trend of DMI observed. We also report four new materials systems with giant DMI and new designs for magnetic multilayers that are expected to outperform the best materials known so far. Our results present a notably new understanding of DMI, uncover highly promising materials and put forth pathways for the controlled generation of skyrmions.
Modeling Intercalated Group-4-Metal Nitride Halide Superconductivity with Interlayer Coulomb Coupling

Behavior consistent with Coulomb-mediated high- T C superconductivity is shown to be present in the intercalated group-4-metal nitride halides A x (S) y MNX, where the MNX host (M = Ti, Zr, Hf; X = Cl, Br) is partially intercalated with cations A x and optionally molecular species (S) y in the van der Waals gap between the halide X layers, expanding the basal-plane spacing d. The optimal transition temperature is modeled by T C0 ∝ ζ −1(σ/ A)1/2, where the participating fractional charge per area per formula unit σ/A and the distance ζ, given by the transverse A x -X separation (ζ < d), govern the interlayer Coulomb coupling. From experiment results for β-form compounds based on Zr and Hf, in which concentrations x of A x are varied, it is shown that σ = γ[ v(x opt − x 0)], where x opt is the optimal doping, x 0 is the onset of superconducting behavior, v is the A x charge state, and γ = 1/8 is a factor determined by the model. Observations of T C < T C0 in the comparatively more disordered α-A x (S) y TiNX compounds are modeled as pair breaking by remote Coulomb scattering from the A x cations, which attenuates exponentially with increasing ζ. The T C0 values calculated for nine A x (S) y MNCl compounds, shown to be optimal, agree with the measured T C to within experimental error. The model for T C0 is also found to be consistent with the absence of high- T C characteristics for A x MNX compounds in which a spatially separated intercalation layer is not formed.
Nuclear Physics in a Susy Universe

We refine a previous zeroth-order analysis of the nuclear properties of a supersymmetric (SUSY) universe with standard model particle content plus degenerate SUSY partners. No assumptions are made concerning the Higgs structure except we assume that the degenerate fermion/sfermion masses are nonzero. This alternate universe has been dubbed Susyria and it has been proposed that such a world may exist with zero vacuum energy in the string landscape.
Hybrid optical-thermal devices and materials for light manipulation and radiative cooling

We report on optical design and applications of hybrid meso-scale devices and materials that combine optical and thermal management functionalities owing to their tailored resonant interaction with light in visible and infrared frequency bands. We outline a general approach to designing such materials, and discuss two specific applications in detail. One example is a hybrid optical-thermal antenna with sub-wavelength light focusing, which simultaneously enables intensity enhancement at the operating wavelength in the visible and reduction of the operating temperature. The enhancement is achieved via light recycling in the form of whispering-gallery modes trapped in an optical microcavity, while cooling functionality is realized via a combination of reduced optical absorption and radiative cooling. The other example is a fabric that is opaque in the visible range yet highly transparent in the infrared, which allows the human body to efficiently shed energy in the form of thermal emission. Such fabrics can find numerous applications for personal thermal management and for buildings energy efficiency improvement.
TIDAL EVOLUTION OF A SECULARLY INTERACTING PLANETARY SYSTEM

In a multi-planet system, a gradual change in one planet's semimajor axis will affect the eccentricities of all the planets, as angular momentum is distributed via secular interactions. If tidal dissipation in the planet is the cause of the change in semimajor axis, it also damps that planet's eccentricity, which in turn also contributes to the evolution of all the eccentricities. Formulae quantifying the combined effects on the whole system due to semimajor axis changes, as well as eccentricity damping, are derived here for a two-planet system. The CoRoT 7 system is considered as an example.
Wave Packets in Honeycomb Structures and Two-Dimensional Dirac Equations

In a recent article (Fefferman and Weinstein, in J Am Math Soc 25:1169–1220, 2012), the authors proved that the non-relativistic Schrodinger operator with a generic honeycomb lattice potential has conical (Dirac) points in its dispersion surfaces. These conical points occur for quasi-momenta, which are located at the vertices of the Brillouin zone, a regular hexagon. In this paper, we study the time-evolution of wave-packets, which are spectrally concentrated near such conical points. We prove that the large, but finite, time dynamics is governed by the two-dimensional Dirac equations.
Small-Scale, Local Area, and Transitional Millimeter Wave Propagation for 5G Communications

This paper studies radio propagation mechanisms that impact handoffs, air interface design, beam steering, and multiple-input multiple-output for 5G mobile communication systems. Knife-edge diffraction (KED) and a creeping wave linear model are shown to predict diffraction loss around typical building objects from 10 to 26 GHz, and human blockage measurements at 73 GHz are shown to fit a double KED model, which incorporates antenna gains. Small-scale spatial fading of millimeter wave (mmWave)-received signal voltage amplitude is generally Ricean-distributed for both omnidirectional and directional receive antenna patterns under both line-of-sight (LOS) and non-line-of-sight (NLOS) conditions in most cases, although the log-normal distribution fits measured data better for the omnidirectional receive antenna pattern in the NLOS environment. Small-scale spatial autocorrelations of received voltage amplitudes are shown to fit sinusoidal exponential and exponential functions for LOS and NLOS environments, respectively, with small decorrelation distances of 0.27–13.6 cm (smaller than the size of a handset) that are favorable for spatial multiplexing. Local area measurements using cluster and route scenarios show how the received signal changes as the mobile moves and transitions from LOS to NLOS locations, with reasonably stationary signal levels within clusters. Wideband mmWave power levels are shown to fade from 0.4 dB/ms to 40 dB/s, depending on travel speed and surroundings.
Protocols for dynamically probing topological edge states and dimerization with fermionic atoms in optical potentials

Topological behavior has been observed in quantum systems including ultracold atoms. However, background harmonic traps for cold atoms hinder the direct detection of topological edge states arising at the boundary because the distortion fuses the edge states into the bulk. We propose experimentally feasible protocols to probe localized edge states and dimerization of ultracold fermions. By confining cold atoms in a ring lattice and changing the boundary condition from periodic to open using an off-resonant laser sheet to cut open the ring, topological edge states can be generated. A lattice in a topological configuration can trap a single particle released at the edge as the system evolves in time. Alternatively, depleting an initially filled lattice away from the boundary reveals the occupied edge states. Signatures of dimerization in the presence of contact interactions can be found in selected correlations as the system boundary suddenly changes from periodic to open and exhibit memory effects of the initial state distinguishing different configurations.
The Nonlinear Heat Equation on W-Random Graphs

For systems of coupled differential equations on a sequence of W-random graphs, we derive the continuum limit in the form of an evolution integral equation. We prove that solutions of the initial value problems (IVPs) for the discrete model converge to the solution of the IVP for its continuum limit. These results combined with the analysis of nonlocally coupled deterministic networks in Medvedev (The nonlinear heat equation on dense graphs and graph limits. ArXiv e-prints, 2013) justify the continuum (thermodynamic) limit for a large class of coupled dynamical systems on convergent families of graphs.
Lagrangian tracking of colliding droplets

We introduce a new Lagrangian particle tracking algorithm that tracks particles in three dimensions to separations between trajectories approaching contact. The algorithm also detects low Weber number binary collisions that result in coalescence as well as droplet breakup. Particles are identified in two-dimensional high-resolution digital images by finding sets of circles to describe the edge of each body. This allows identification of particles that overlap in projection by over 80% even for noisy images and without invoking additional temporal data. The algorithm builds trajectories from three-dimensional particle coordinates by minimizing a penalty function that is a weighted sum of deviations from the expected particle coordinates using information from four moments in time. This new hybrid algorithm is validated against synthetic data and found to perfectly reproduce more trajectories than other commonly used methods. Collisions are detected with 95% accuracy for particles that move on average less than one tenth the distance to their nearest neighbor.
Role of thermal resistance on the performance of superconducting radio frequency cavities

Thermal stability is an important parameter for the operation of the superconducting radio frequency (SRF) cavities used in particle accelerators. The rf power dissipated on the inner surface of the cavities is conducted to the helium bath cooling the outer cavity surface and the equilibrium temperature of the inner surface depends on the thermal resistance. In this manuscript, we present the results of direct measurements of thermal resistance on 1.3 GHz single cell SRF cavities made from high purity large-grain and fine-grain niobium as well as their rf performance for different treatments applied to outer cavity surface in order to investigate the role of the Kapitza resistance to the overall thermal resistance and to the SRF cavity performance. The results show no significant impact of the thermal resistance to the SRF cavity performance after chemical polishing, mechanical polishing or anodization of the outer cavity surface. Temperature maps taken during the rf test show nonuniform heating of the surface at medium rf fields. Calculations of ${Q}_{0}({B}_{p})$ curves using the thermal feedback model show good agreement with experimental data at 2 and 1.8 K when a pair-braking term is included in the calculation of the Bardeen-Cooper-Schrieffer surface resistance. These results indicate local intrinsic nonlinearities of the surface resistance, rather than purely thermal effects, to be the main cause for the observed field dependence of ${Q}_{0}({B}_{p})$.
Restriction Bounds for the Free Resolvent and Resonances in Lossy Scattering

We establish high energy L2 estimates for the restriction of the free Green’s function to hypersurfaces in R, d ≥ 1. As an application, we estimate the size of a logarithmic resonance free region for scattering by potentials of the form V ⊗ δΓ, where Γ ⊂ R is a finite union of compact subsets of embedded hypersurfaces. In odd dimensions we prove a resonance expansion for solutions to the wave equation with such a potential.
Holography for field theory solitons

We extend a well-known D-brane construction of the AdS/dCFT correspondence to non-abelian defects. We focus on the bulk side of the correspondence and show that there exists a regime of parameters in which the low-energy description consists of two approximately decoupled sectors. The two sectors are gravity in the ambient spacetime, and a six-dimensional supersymmetric Yang-Mills theory. The Yang-Mills theory is defined on a rigid AdS4 × S 2 background and admits sixteen supersymmetries. We also consider a one-parameter deformation that gives rise to a family of Yang-Mills theories on asymptotically AdS4 × S 2 spacetimes, which are invariant under eight supersymmetries. With future holographic applications in mind, we analyze the vacuum structure and perturbative spectrum of the Yang-Mills theory on AdS4 × S 2, as well as systems of BPS equations for finite-energy solitons. Finally, we demonstrate that the classical Yang-Mills theory has a consistent truncation on the two-sphere, resulting in maximally supersymmetric Yang-Mills on AdS4.
Mean turbulence statistics in boundary layers over high-porosity foams

This paper reports turbulent boundary layer measurements made over open-cell reticulated foams with varying pore size and thickness, but constant porosity ( ). The foams were flush-mounted into a cutout on a flat plate. A laser Doppler velocimeter (LDV) was used to measure mean streamwise velocity and turbulence intensity immediately upstream of the porous section, and at multiple measurement stations along the porous substrate. The friction Reynolds number upstream of the porous section was . For all but the thickest foam tested, the internal boundary layer was fully developed by downstream from the porous transition, where is the boundary layer thickness. Fully developed mean velocity profiles showed the presence of a substantial slip velocity at the porous interface ( of the free-stream velocity) and a mean velocity deficit relative to the canonical smooth-wall profile further from the wall. While the magnitude of the mean velocity deficit increased with average pore size, the slip velocity remained approximately constant. Fits to the mean velocity profile suggest that the logarithmic region is shifted relative to a smooth wall, and that this shift increases with pore size until it becomes comparable to substrate thickness . For all foams, the turbulence intensity was found to be elevated further into the boundary layer to . An outer peak in intensity was also evident for the largest pore sizes. Velocity spectra indicate that this outer peak is associated with large-scale structures resembling Kelvin–Helmholtz vortices that have streamwise length scale . Skewness profiles suggest that these large-scale structures may have an amplitude-modulating effect on the interfacial turbulence.
Critical shear rate and torque stability condition for a particle resting on a surface in a fluid flow

We advance a quantitative description of the critical shear rate needed to dislodge a spherical particle resting on a surface with a model asperity in laminar and turbulent fluid flows. We have built a cone-plane experimental apparatus which enables measurement of over a wide range of particle Reynolds number from to . The condition to dislodge the particle is found to be consistent with the torque balance condition after including the torque component due to drag about the particle centre. The data for are in good agreement with analytical calculations of the drag and lift coefficients in the limit. For higher , where analytical results are unavailable, the hydrodynamic coefficients are found to approach a constant for . We show that a linear combination of the hydrodynamic coefficients found in the viscous and inertial limits can describe the observed as a function of the particle and fluid properties.
Core and Filament Formation in Magnetized, Self-gravitating Isothermal Layers

We examine the role of the gravitational instability in an isothermal, self-gravitating layer threaded by magnetic fields on the formation of filaments and dense cores. Using a numerical simulation, we follow the non-linear evolution of a perturbed equilibrium layer. The linear evolution of such a layer is described in the analytic work of Nagai et al. We find that filaments and dense cores form simultaneously. Depending on the initial magnetic field, the resulting filaments form either a spiderweb-like network (for weak magnetic fields) or a network of parallel filaments aligned perpendicular to the magnetic field lines (for strong magnetic fields). Although the filaments are radially collapsing, the density profile of their central region (up to the thermal scale height) can be approximated by a hydrodynamical equilibrium density structure. Thus, the magnetic field does not play a significant role in setting the density distribution of the filaments. The density distribution outside of the central region deviates from the equilibrium. The radial column density distribution is then flatter than the expected power law of r –4 and similar to filament profiles observed with Herschel. Our results do not explain the near constant filament width of ~0.1pc. However, our model does not include turbulent motions. It is expected that the accretion-driven amplification of these turbulent motions provides additional support within the filaments against gravitational collapse. Finally, we interpret the filamentary network of the massive star forming complex G14.225-0.506 in terms of the gravitational instability model and find that the properties of the complex are consistent with being formed out of an unstable layer threaded by a strong, parallel magnetic field.
The gravitino coupling to broken gauge theories applied to the MSSM

We consider gravitino couplings in theories with broken gauge symmetries. In particular, we compute the single gravitino production cross section in the W + W − fusion process. Despite recent claims to the contrary, we show that this process is always subdominant to gluon fusion processes in the high energy limit. The full calculation is performed numerically; however, we give analytic expressions for the cross section in the supersymmetric and electroweak limits. We also confirm these results with the use of the effective theory of goldstino interactions.
TRIGGER MECHANISM OF SOLAR SUBFLARES IN A BRAIDED CORONAL MAGNETIC STRUCTURE

Fine-scale braiding of coronal magnetic loops by continuous footpoint motions may power coronal heating via nanoflares, which are spontaneous fine-scale bursts of internal reconnection. An initial nanoflare may trigger an avalanche of reconnection of the braids, making a microflare or larger subflare. In contrast to this internal triggering of subflares, we observe external triggering of subflares in a braided coronal magnetic field observed by the High-resolution Coronal Imager (Hi-C). We track the development of these subflares using 12 s cadence images acquired by SDO/AIA in 1600, 193, 94 A, and registered magnetograms of SDO/HMI, over four hours centered on the Hi-C observing time. These data show numerous recurring small-scale brightenings in transition-region emission happening on polarity inversion lines where flux cancellation is occurring. We present in detail an example of an apparent burst of reconnection of two loops in the transition region under the braided coronal field which is appropriate for releasing a short reconnected loop downward and a longer reconnected loop upward. The short loop presumably submerges into the photosphere, participating in observed flux cancellation. A subflare in the overlying braided magnetic field is apparently triggered by the disturbance of the braided field by the reconnection-released upward loop. At leastmore » 10 subflares observed in this braided structure appear to be triggered this way. How common this external trigger mechanism for coronal subflares is in other active regions, and how important it is for coronal heating in general, remain to be seen.« less
Proper affine actions in non-swinging representations

For a semisimple real Lie group $G$ with an irreducible representation $\rho$ on a finite-dimensional real vector space $V$, we give a sufficient criterion on $\rho$ for existence of a group of affine transformations of $V$ whose linear part is Zariski-dense in $\rho(G)$ and that is free, nonabelian and acts properly discontinuously on $V$.
A 5-dimensional Tonnetz for nearly symmetric hexachords

The standard 2-dimensional Tonnetz describes parsimonious voice leading connections between major and minor triads as the 3-dimensional Tonnetz does for dominant seventh and half-diminished seventh...
Stability in the homology of unipotent groups

Let R be a (not necessarily commutative) ring whose additive group is finitely generated and let U n ( R ) ⊂ G L n ( R ) be the group of upper-triangular unipotent matrices over R . We study how the homology groups of U n ( R ) vary with n from the point of view of representation stability. Our main theorem asserts that if for each n we have representations M n of U n ( R ) over a ring k that are appropriately compatible and satisfy suitable finiteness hypotheses, then the rule [ n ] ↦ H i ( U n ( R ) , M n ) defines a finitely generated O I -module. As a consequence, if k is a field then dim H i ( U n ( R ) , k ) is eventually equal to a polynomial in n . We also prove similar results for the Iwahori subgroups of G L n ( 𝒪 ) for number rings 𝒪 .
On homology cobordism and local equivalence between plumbed manifolds

We establish a structural understanding of the involutive Heegaard Floer homology for all linear combinations of almost-rational (AR) plumbed three-manifolds. We use this to show that the Neumann-Siebenmann invariant is a homology cobordism invariant for all linear combinations of AR plumbed homology spheres. As a corollary, we prove that if $Y$ is a linear combination of AR plumbed homology spheres with $\mu(Y) = 1$, then $Y$ is not torsion in the homology cobordism group. A general computation of the involutive Heegaard Floer correction terms for these spaces is also included.
Charm, bottom, strange baryon masses using QCD sum rules

We use the method of QCD Sum Rules to estimate the masses of the charm baryon, $\Lambda^+_c$, bottom baryon $\Lambda^0_b$, strange baryon $\Lambda^0_s$ and compare them to their experimental values.
Resolving the Weinberg paradox with topology

Long ago Weinberg showed, from first principles, that the amplitude for a single photon exchange between an electric current and a magnetic current violates Lorentz invariance. The obvious conclusion at the time was that monopoles were not allowed in quantum field theory. Since the discovery of topological monopoles there has thus been a paradox. On the one hand, topological monopoles are constructed in Lorentz invariant quantum field theories, while on the other hand, the low-energy effective theory for such monopoles will reproduce Weinberg’s result. We examine a toy model where both electric and magnetic charges are perturbatively coupled and show how soft-photon resummation for hard scattering exponentiates the Lorentz violating pieces to a phase that is the covariant form of the Aharonov-Bohm phase due to the Dirac string. The modulus of the scattering amplitudes (and hence observables) are Lorentz invariant, and when Dirac charge quantization is imposed the amplitude itself is also Lorentz invariant. For closed paths there is a topological component of the phase that relates to aspects of 4D topological quantum field theory.
Single-photon absorption by single photosynthetic light-harvesting complexes

Author(s): Chan, HCH; Gamel, OE; Fleming, GR; Whaley, KB | Abstract: We provide a unified theoretical approach to the quantum dynamics of absorption of single photons and subsequent excitonic energy transfer in photosynthetic light-harvesting complexes. Our analysis combines a continuous mode ?n?-photon quantum optical master equation for the chromophoric system with the hierarchy of equations of motion describing excitonic dynamics in presence of non-Markovian coupling to vibrations of the chromophores and surrounding protein. We apply the approach to simulation of absorption of single-photon coherent states by pigment protein complexes containing between one and seven chromophores, and compare with results obtained by excitation using a thermal radiation field. We show that the values of excitation probability obtained under single-photon absorption conditions can be consistently related to bulk absorption cross-sections. Analysis of the timescale and efficiency of single-photon absorption by light-harvesting systems within this full quantum description of pigment protein dynamics coupled to a quantum radiation field reveals a non-trivial dependence of the excitation probability and the excited state dynamics induced by exciton-phonon coupling during and subsequent to the pulse, on the bandwidth of the incident photon pulse. For bandwidths equal to the spectral bandwidth of Chlorophyll a, our results yield an estimation of an average time of ?0.09 s for a single chlorophyll chromophore to absorb the energy equivalent of one (singlepolarization) photon under irradiation by single-photon states at the intensity of sunlight.
Liouville Integrability of a Class of Integrable Spin Calogero-Moser Systems and Exponents of Simple Lie Algebras

In previous work, we introduced a class of integrable spin Calogero-Moser systems associated with the classical dynamical r-matrices with spectral parameter, as classified by Etingof and Varchenko for simple Lie algebras. Here the main purpose is to establish the Liouville integrability of these systems by a uniform method based on evaluating the primitive invariants of Chevalley on the Lax operators with spectral parameter. As part of our analysis, we will develop several results concerning the algebra of invariant polynomials on simple Lie algebras and their expansions.
The evolution of lossy compression.

In complex environments, there are costs to both ignorance and perception. An organism needs to track fitness-relevant information about its world, but the more information it tracks, the more resources it must devote to perception. As a first step towards a general understanding of this trade-off, we use a tool from information theory, rate–distortion theory, to study large, unstructured environments with fixed, randomly drawn penalties for stimuli confusion (‘distortions’). We identify two distinct regimes for organisms in these environments: a high-fidelity regime where perceptual costs grow linearly with environmental complexity, and a low-fidelity regime where perceptual costs are, remarkably, independent of the number of environmental states. This suggests that in environments of rapidly increasing complexity, well-adapted organisms will find themselves able to make, just barely, the most subtle distinctions in their environment.
THE LICK-CARNEGIE SURVEY: A NEW TWO-PLANET SYSTEM AROUND THE STAR HD 207832

Keck/HIRES precision radial velocities of HD 207832 indicate the presence of two Jovian-type planetary companions in Keplerian orbits around this G star. The planets have minimum masses of Msin i = 0.56 M Jup and 0.73 M Jup, with orbital periods of ~162 and ~1156 days, and eccentricities of 0.13 and 0.27, respectively. Stromgren b and y photometry reveals a clear stellar rotation signature of the host star with a period of 17.8 days, well separated from the period of the radial velocity variations, reinforcing their Keplerian origin. The values of the semimajor axes of the planets suggest that these objects have migrated from the region of giant planet formation to closer orbits. In order to examine the possibility of the existence of additional (small) planets in the system, we studied the orbital stability of hypothetical terrestrial-sized objects in the region between the two planets and interior to the orbit of the inner body. Results indicated that stable orbits exist only in a small region interior to planet b. However, the current observational data offer no evidence for the existence of additional objects in this system.
Demographics of Planetesimals Formed by the Streaming Instability

NASA headquarters under the NASA Earth and Space Science Fellowship ProgramNational Aeronautics & Space Administration (NASA) [NNX16AP53H]; NASA Astrophysics Theory Grant [NNX17AK59G]; NSFNational Science Foundation (NSF) [AST-1616929]
Quantization of Hall Conductance for Interacting Electrons on a Torus

We consider interacting, charged spins on a torus described by a gapped Hamiltonian with a unique groundstate and conserved local charge. Using quasi-adiabatic evolution of the groundstate around a flux-torus, we prove, without any averaging assumption, that the Hall conductance of the groundstate is quantized in integer multiples of e^2/h, up to exponentially small corrections in the linear size L. In addition, we discuss extensions to the fractional quantization case under an additional topological order assumption on the degenerate groundstate subspace.
The Optimal Sink and the Best Source in a Markov Chain

It is well known that the distributions of hitting times in Markov chains are quite irregular, unless the limit as time tends to infinity is considered. We show that nevertheless for a typical finite irreducible Markov chain and for nondegenerate initial distributions the tails of the distributions of the hitting times for the states of a Markov chain can be ordered, i.e., they do not overlap after a certain finite moment of time. If one considers instead each state of a Markov chain as a source rather than a sink then again the states can generically be ordered according to their efficiency. The mechanisms underlying these two orderings are essentially different though. Our results can be used, e.g., for a choice of the initial distribution in numerical experiments with the fastest convergence to equilibrium/stationary distribution, for characterization of the elements of a dynamical network according to their ability to absorb and transmit the substance (“information”) that is circulated over the network, for determining optimal stopping moments (stopping signals/words) when dealing with sequences of symbols, etc.
Melting Hadrons, Boiling Quarks

In the context of the Hagedorn temperature half-centenary I describe our understanding of the hot phases of hadronic matter both below and above the Hagedorn temperature. The first part of the review addresses many frequently posed questions about properties of hadronic matter in different phases, phase transition and the exploration of quark-gluon plasma (QGP). The historical context of the discovery of QGP is shown and the role of strangeness and strange antibaryon signature of QGP illustrated. In the second part I discuss the corresponding theoretical ideas and show how experimental results can be used to describe the properties of QGP at hadronization. The material of this review is complemented by two early and unpublished reports containing the prediction of the different forms of hadron matter, and of the formation of QGP in relativistic heavy ion collisions, including the discussion of strangeness, and in particular strange antibaryon signature of QGP.
Autoregressive Knowledge Distillation through Imitation Learning

The performance of autoregressive models on natural language generation tasks has dramatically improved due to the adoption of deep, self-attentive architectures. However, these gains have come at the cost of hindering inference speed, making state-of-the-art models cumbersome to deploy in real-world, time-sensitive settings. We develop a compression technique for autoregressive models that is driven by an imitation learning perspective on knowledge distillation. The algorithm is designed to address the exposure bias problem. On prototypical language generation tasks such as translation and summarization, our method consistently outperforms other distillation algorithms, such as sequence-level knowledge distillation. Student models trained with our method attain 1.4 to 4.8 BLEU/ROUGE points higher than those trained from scratch, while increasing inference speed by up to 14 times in comparison to the teacher model.
Divergence-free magnetohydrodynamics on conformally moving, adaptive meshes using a vector potential method

Abstract We present a new method for evolving the equations of magnetohydrodynamics (both Newtonian and relativistic) that is capable of maintaining a divergence-free magnetic field ( ∇ ⋅ B = 0 ) on adaptively refined, conformally moving meshes. The method relies on evolving the magnetic vector potential and then using it to reconstruct the magnetic fields. The advantage of this approach is that the vector potential is not subject to a constraint equation in the same way the magnetic field is, and so can be refined and moved in a straightforward way. We test this new method against a wide array of problems from simple Alfven waves on a uniform grid to general relativistic MHD simulations of black hole accretion on a nested, spherical-polar grid. We find that the code produces accurate results and in all cases maintains a divergence-free magnetic field to machine precision.
HST/ACS Imaging of Omega Centauri: Optical Counterparts of Chandra X-Ray Sources

We present results of a search for optical counterparts of X-ray sources in and toward the globular cluster Omega Centauri (NGC 5139) using the Advanced Camera for Surveys (ACS) on the Hubble Space Telescope. The ACS data consist of a mosaic of Wide Field Channel images obtained using F625W, F435W, and F658N filters; with nine pointings we cover the central ~10' × 10' of the cluster and encompass 109 known Chandra sources. We find promising optical counterparts for 59 of the sources, ~40 of which are likely to be associated with the cluster. These include 27 candidate cataclysmic variables (CVs), 24 of which are reported here for the first time. Fourteen of the CV candidates are very faint, with absolute magnitudes in the range M 625 =10.4-12.6, making them comparable in brightness to field CVs near the period minimum discovered in the Sloan Digital Sky Survey. Additional optical counterparts include three BY Dra candidates, a possible blue straggler, and a previously reported quiescent low-mass X-ray binary. We also identify 3 foreground stars and 11 probable active galactic nuclei. Finally, we report the discovery of a group of seven stars whose X-ray properties are suggestive of magnetically active binaries, and whose optical counterparts lie on or very near the metal-rich anomalous giant and subgiant branches in ω Cen. If the apparent association between these seven stars and the RGB/SGB-a stars is real, then the frequency of X-ray sources in this metal-rich population is enhanced by a factor of at least five relative to the other giant and subgiant populations in the cluster. If these stars are not members of the metal-rich population, then they bring the total number of red stragglers (also known as sub-subgiants) that have been identified in ω to Cen 20, the largest number yet known in any globular cluster.
Convexity of Reduced Energy and Mass Angular Momentum Inequalities

In this paper, we extend the work in Chruściel and Costa (Class. Quant. Grav. 26:235013, 2009), Chruściel et al. (Ann. Phy. 323:2591–2613, 2008), Costa (J. Math. Theor. 43:285202, 2010), Dain (J. Diff. Geom. 79:33–67, 2008). We weaken the asymptotic conditions on the second fundamental form, and we also give an L6−norm bound for the difference between general data and Extreme Kerr data or Extreme Kerr–Newman data by proving convexity of the renormalized Dirichlet energy when the target has non-positive curvature. In particular, we give the first proof of the strict mass/angular momentum/charge inequality for axisymmetric Einstein/Maxwell data which is not identical with the extreme Kerr–Newman solution.
THE DUST ATTENUATION LAW IN DISTANT GALAXIES: EVIDENCE FOR VARIATION WITH SPECTRAL TYPE

This Letter utilizes composite spectral energy distributions (SEDs) constructed from NEWFIRM Medium-Band Survey photometry to constrain the dust attenuation curve in 0.5 < z < 2.0 galaxies. Based on similarities between the full SED shapes (0.3-8 μm), we have divided galaxies in 32 different spectral classes and stacked their photometry. As each class contains galaxies over a range in redshift, the resulting rest-frame SEDs are well sampled in wavelength and show various spectral features including Hα and the UV dust bump at 2175 A. We fit all composite SEDs with flexible stellar population synthesis models, while exploring attenuation curves with varying slopes and UV bump strengths. The Milky Way and Calzetti law provide poor fits at UV wavelengths for nearly all SEDs. Consistent with previous studies, we find that the best-fit attenuation law varies with spectral type. There is a strong correlation between the best-fit dust slope and UV bump strength, with steeper laws having stronger bumps. Moreover, the attenuation curve correlates with specific star formation rate (SFR), with more active galaxies having shallower dust curves and weaker bumps. There is also a weak correlation with inclination. The observed trends can be explained by differences in the dust-to-star geometry, a varying grain size distribution, or a combination of both. Our results have several implications for galaxy evolution studies. First, the assumption of a universal dust model leads to biases in derived galaxy properties. Second, the presence of a dust bump may result in underestimated values for the UV slope, used to correct SFRs of distant galaxies.
Fe XVII X-ray Line Ratios for Accurate Astrophysical Plasma Diagnostics

New laboratory measurements using an electron beam ion trap and an X-ray microcalorimeter are presented for the n = 3 to n = 2 Fe XVII emission lines in the 15-17 A range, along with new theoretical predictions for a variety of electron energy distributions. This work improves upon our earlier work on these lines by providing measurements at more electron-impact energies (seven values from 846 to 1185 eV), performing an in situ determination of the X-ray window transmission, taking steps to minimize the ion impurity concentrations, correcting the electron energies for space charge shifts, and estimating the residual electron energy uncertainties. The results for the 3C/3D and 3s/3C line ratios are generally in agreement with the closest theory to within 10%, and in agreement with previous measurements from an independent group to within 20%. Better consistency between the two experimental groups is obtained at the lowest electron energies by using theory to interpolate, taking into account the significantly different electron energy distributions. Evidence for resonance collision effects in the spectra is discussed. Renormalized values for the absolute cross sections of the 3C and 3D lines are obtained by combining previously published results and shown to be in agreement with the predictions of converged R-matrix theory. This work establishes consistency between results from independent laboratories and improves the reliability of these lines for astrophysical diagnostics. Factors that should be taken into account for accurate diagnostics are discussed, including electron energy distribution, polarization, absorption/scattering, and line blends.
May I Ask Who's Calling? Named Entity Recognition on Call Center Transcripts for Privacy Law Compliance.

We investigate using Named Entity Recognition on a new type of user-generated text: a call center conversation. These conversations combine problems from spontaneous speech with problems novel to conversational Automated Speech Recognition, including incorrect recognition, alongside other common problems from noisy user-generated text. Using our own corpus with new annotations, training custom contextual string embeddings, and applying a BiLSTM-CRF, we match state-of- the-art results on our novel task.
Breathing patterns in nonlinear relaxation

In numerical experiments involving nonlinear solitary waves propagating through nonhomogeneous media one observes 'breathing' in the sense of the amplitude of the wave going up and down on a much faster scale than the motion of the wave. In this paper we investigate this phenomenon in the simplest case of stationary waves in which the evolution corresponds to relaxation to a nonlinear ground state. The particular model is the popular δ0 impurity in the cubic nonlinear Schrodinger equation on the line. We give asymptotics of the amplitude on a finite but relevant time interval and show their remarkable agreement with numerical experiments. We stress the nonlinear origin of the 'breathing patterns' caused by the selection of the ground state depending on the initial data, and by the nonnormality of the linearized operator.
Area laws in a many-body localized state and its implications for topological order

The question whether Anderson insulators can persist to finite-strength interactions?a scenario dubbed many-body localization?has recently received a great deal of interest. The origin of such a many-body localized phase has been described as localization in Fock space, a picture we examine numerically. We then formulate a precise sense in which a single energy eigenstate of a Hamiltonian can be adiabatically connected to a state of a non-interacting Anderson insulator. We call such a state a many-body localized state and define a many-body localized phase as one in which almost all states are many-body localized states. We explore the possible consequences of this; the most striking is an area law for the entanglement entropy of almost all excited states in a many-body localized phase. We present the results of numerical calculations for a one-dimensional system of spinless fermions. Our results are consistent with an area law and, by implication, many-body localization for almost all states and almost all regions for weak enough interactions and strong disorder. However, there are rare regions and rare states with much larger entanglement entropies. Furthermore, we study the implications that many-body localization may have for topological phases and self-correcting quantum memories. We find that there are scenarios in which many-body localization can help to stabilize topological order at non-zero energy density, and we propose potentially useful criteria to confirm these scenarios.
Magnetization around mix jets entering inertial confinement fusion fuel

Engineering features are known to cause jets of ablator materials to enter the fuel hot-spot in inertial confinement fusion implosions. The Biermann battery mechanism wraps them in a self-generated magnetic field. We show that higher-Z jets have an additional thermoelectric magnetic source term that is not present for hydrogen jets, verified here through a kinetic simulation. It has similar magnitude to the Biermann term. We then include this in an extended magneto-hydrodynamic approach to post process an xRAGE radiation-hydrodynamic implosion simulation. The simulation includes an accurate model for the capsule fill tube, producing a dense carbon jet that becomes wrapped in a 4000 T magnetic field. A simple spherical carbon mix model shows that this insulates the electron heat conduction enough to cause contraction of the jet to an optically thick equilibrium. The denser magnetized jet hydrodynamics could change its core penetration and therefore the final mix mass, which is known to be well correlated with fusion yield degradation. Fully exploring this will require self-consistent magneto-hydrodynamic simulations. Experimental signatures of this self-magnetization may emerge in the high energy neutron spectrum.
Inflationary birefringence and baryogenesis

A decade ago, the first leptogenesis model based on inflation was proposed, where the complex phase of the inflaton field carries lepton number [S. H. S. Alexander, M. E. Peskin and M. M. Sheikh-Jabbari, Phys. Rev. Lett. 96 (2006) 081301, arXiv:hep-th/0403069]. If the inflaton field is an axion, it can couple to gravitational waves and gauge fields via Chern–Simons invariants. Due to these couplings, birefringent gravitational and gauge primordial perturbations are created during inflation to generate a lepton asymmetry, establishing a possible connection between nonvanishing TB-parity-violating polarization cross-correlations and leptogenesis. We also discuss the prospect for a subset of these models which can directly source circular (V-mode) polarization in the CMB.