cssi/SciSciGPT-SciSciNet huggingface dataset:
An intrinsic absorption complex toward RX J1230.8+0115: Geometry and photoionization conditions

We present Hubble Space Telescope/Space Telescope Imaging Spectrograph and Far Ultraviolet Spectroscopic Explorer spectra of the quasar RX J1230.8+0115 (V = 14.4,z = 0.117). In addition to Galactic, Virgo, and intervening absorption, this quasar is host to a remarkable intrinsic absorption complex. Four narrow absorption line systems, strong in C IV, N V, and O VI, lie within 5000 km s-1 of the QSO redshift. Three of the systems appear to be line locked, two in N V and two in O VI, with the common system residing in between the other two (in velocity). All three systems show signs of an intrinsic origin—smooth windlike profiles, high ionization, and partial coverage of the central engine. The fourth system, which appears at the systemic redshift of the QSO, may originate from host galaxy or intervening gas. Photoionization analyses imply column densities in the range 19.1 < log N(H) < 21 and ionization parameters in the range -1.3 < log U < 0.3. Revisiting the issue of line locking, we discuss a possible model in the context of the accretion disk/wind scenario and point out several issues that remain for future simulations and observations.
Holomorphic Lagrangian branes correspond to perverse sheaves

Let X be a compact complex manifold, D c .X / be the bounded derived category of constructible sheaves on X , and Fuk.T X / be the Fukaya category of T X . A Lagrangian brane in Fuk.T X / is holomorphic if the underlying Lagrangian submanifold is complex analytic in T XC , the holomorphic cotangent bundle of X . We prove that under the quasiequivalence between D c .X / and DFuk.T X / established by Nadler and Zaslow, holomorphic Lagrangian branes with appropriate grading correspond to perverse sheaves.
Transport and thermodynamics in quantum junctions: A scattering approach

We present a scattering approach for the study of the transport and thermodynamics of quantum systems strongly coupled to their thermal environment(s). This formalism recovers the standard non-equilibrium Green's function expressions for quantum transport and reproduces recently obtained results for the quantum thermodynamics of slowly driven systems. Using this approach, new results have been obtained. First, we derived a general explicit expression for the non-equilibrium steady-state density matrix of a system composed of multiple infinite baths coupled through a general interaction. Then, we obtained a general expression for the dissipated power for the driven non-interacting resonant level to the first order in the driving speeds, where both the dot energy level and its couplings are changing, without invoking the wide-band approximation. In addition, we also showed that the symmetric splitting of the system bath interaction, employed for the case of a system coupled to one bath to determine the effective system Hamiltonian [A. Bruch et al., Phys. Rev. B 93, 115318 (2016)], is valid for the multiple bath case as well. Finally, we demonstrated an equivalence of our method to the Landauer-Buttiker formalism and its extension to slowly driven systems developed by Bruch, Lewenkopf, and von Oppen [Phys. Rev. Lett. 120, 107701 (2018)]. To demonstrate the use of this formalism, we analyze the operation of a device in which the dot is driven cyclically between two leads under strong coupling conditions. We also generalize the previously obtained expression for entropy production in such driven processes to the many-bath case.
Programmable Interference between Two Microwave Quantum Memories

New experiments demonstrate on-demand interference between stationary modes stored in separated superconducting microwave cavities, enabling future studies of complex quantum interference phenomena critical to fundamental science and quantum information applications.
AN EMPIRICAL DETERMINATION OF THE INTERGALACTIC BACKGROUND LIGHT FROM UV TO FIR WAVELENGTHS USING FIR DEEP GALAXY SURVEYS AND THE GAMMA-RAY OPACITY OF THE UNIVERSE

Author(s): Stecker, Floyd W; Scully, Sean T; Malkan, Matthew A | Abstract: We have previously calculated the intergalactic background light (IBL) as a function of redshift in the far ultraviolet to near infrared range, based purely on data from deep galaxy surveys. Here we utilize similar methods to determine the mid- and far infrared IBL out to a wavelength of 850 microns. Our approach enables us to constrain the range of photon densities, based on the uncertainties from observationally determined luminosity densities and colors. By also including the effect of the 2.7 K cosmic background photons, we determine 68% confidence upper and lower limits on the opacity of the universe to gamma-rays up to PeV energies. Our direct results on the IBL are consistent with those from complimentary gamma-ray analyses using observations from the Fermi $\gamma$-ray space telescope and the H.E.S.S. air Cherenkov telescope. Thus, we find no evidence of previously suggested processes for the modification of gamma-ray spectra other than that of absorption by pair production alone.
BOSS Ultracool Dwarfs. I. Colors and Magnetic Activity of M and L Dwarfs

We present the colors and activity of ultracool (M7?L8) dwarfs from the Tenth Data Release of the Sloan Digital Sky Survey (SDSS). We combine previous samples of SDSS M and L dwarfs with new data obtained from the Baryon Oscillation Sky Survey (BOSS) to produce the BOSS Ultracool Dwarf (BUD) sample of 11820 M7?L8 dwarfs. By combining SDSS data with photometry from 2MASS and the Wide-field Infrared Sky Explorer (WISE) mission, we present ultracool dwarf colors from to as a function of spectral type, and extend the SDSS?2MASS?WISE color locus to include ultracool dwarfs. The , , and colors provide the best indication of spectral type for M7?L3 dwarfs. We also examine ultracool dwarf chromospheric activity through the presence and strength of H? emission. The fraction of active dwarfs rises through the M spectral sequence until it reaches ?90% at spectral type L0. The fraction of active dwarfs then declines to 50% at spectral type L5; no H? emission is observed in the late-L dwarfs in the BUD sample. The fraction of active L0?L5 dwarfs is much higher than previously observed. The strength of activity declines with spectral type from M7 through L3, after which the data do not show a clear trend. Using one-dimensional chromosphere models, we explore the range of filling factors and chromospheric temperature structures that are consistent with H? observations of M0?L7 dwarfs. M dwarf chromospheres have a similar, smoothly varying range of temperature and surface coverage, while L dwarf chromospheres are cooler and have smaller filling factors.
Large piezoelectric response of van der Waals layered solids

The bulk piezoelectric response, as measured by the piezoelectric modulus tensor (d), is determined by a combination of charge redistribution due to strain and the amount of strain produced by the application of stress (stiffness). Motivated by the notion that less stiff materials could exhibit large piezoelectric responses, herein, we investigate the piezoelectric modulus of van der Waals (vdW) layered materials using first-principles calculations. From a pool of 869 known binary and ternary quasi-2D layered materials, we have identified 135 non-centrosymmetric crystals of which 51 are found to have piezoelectric modulus tensor (d) components larger than the longitudinal piezoelectric modulus of AlN, a commonly used piezoelectric material for resonators. We have also identified three materials with d components larger than that of PbTiO3, which is among the materials with the largest known piezoelectric modulus. None of the identified materials have previously been considered for piezoelectric applications. Furthermore, we find that large d components are always coupled to the shear or axial deformations of the vdW gap between the layers and are indeed enabled by the weak inter-layer interactions.
Quantum Hall states and conformal field theory on a singular surface

In [Can et al. 2016], quantum Hall states on singular surfaces were shown to possess an emergent conformal symmetry. In this paper, we develop this idea further and flesh out details on the emergent conformal symmetry in holomorphic adiabatic states, which we define in the paper. We highlight the connection between the universal features of geometric transport of quantum Hall states and holomorphic dimension of primary fields in conformal field theory. In parallel we compute the universal finite-size corrections to the free energy of a critical system on a hyperbolic sphere with conical and cusp singularities, thus extending the result of Cardy and Peschel for critical systems on a flat cone [Cardy, Peschel 1988], and the known results for critical systems on polyhedra and flat branched Riemann surfaces.
Understanding and Predicting Travel Time with Spatio-Temporal Features of Network Traffic Flow, Weather and Incidents

Travel time on a route varies substantially by time of day and from day to day. It is critical to understand to what extent this variation is correlated with various factors, such as weather, incidents, events or travel demand level in the context of dynamic networks. This helps a better decision making for infrastructure planning and real-time traffic operation. We propose a data-driven approach to understand and predict highway travel time using spatio-temporal features of those factors, all of which are acquired from multiple data sources. The prediction model holistically selects the most related features from a highdimensional feature space by correlation analysis, principle component analysis and LASSO. We test and compare the performance of several regression models in predicting travel time 30 min in advance via two case studies: (1) a 6-mile highway corridor of I-270N in D.C. region, and (2) a 2.3-mile corridor of I-376E in Pittsburgh region. We found that some bottlenecks scattered in the network can imply congestion on those corridors at least 30 minutes in advance, including those on the alternative route to the corridors of study. In addition, real-time travel time is statistically related to incidents on some specific locations, morning/afternoon travel demand, visibility, precipitation, wind speed/gust and the weather type. All those spatiotemporal information together help improve prediction accuracy, comparing to using only speed data. In both case studies, random forest shows the most promise, reaching a root-mean-squared error of 16.6% and 17.0% respectively in afternoon peak hours for the entire year of 2014.
Octonions, Monopoles, and Knots

Witten’s approach to Khovanov homology of knots is based on the ve-dimensional system of partial dierential equations, which we call Haydys-Witten equations. We argue for a one-to-one correspondence between its solutions and solutions of the seven-dimensional system of equations. The latter can be formulated on any G2 holonomy manifold and is a close cousin of the monopole equation of Bogomolny. Octonions play the central role in our view, in which both the sevendimensional equations and the Haydys-Witten equations appear as reductions of the eight-dimensional Spin(7) instanton equation.
Localization and stationary phase approximation on supermanifolds

Given an odd vector field Q on a supermanifold M and a Q-invariant density μ on M, under certain compactness conditions on Q, the value of the integral ∫Mμ is determined by the value of μ on any neighborhood of the vanishing locus N of Q. We present a formula for the integral in the case where N is a subsupermanifold which is appropriately non-degenerate with respect to Q. In the process, we discuss the linear algebra necessary to express our result in a coordinate independent way. We also extend the stationary phase approximation and the Morse-Bott lemma to supermanifolds.
Implications of the TTV-detection of close-in terrestrial planets around M stars for their origin and dynamical evolution

It has been shown that an Earth-size planet or a super-Earth, in resonance with a transiting Jupiter-like body around an M star, can create detectable TTV signals (Kirste & Haghighipour, 2011). Given the low masses of M stars and their circumstellar disks, it is expected that the transiting giant planet to have formed at large distances and migrated to its close-in orbit. That implies, the terrestrial planet has to form during the migration of the giant planet, be captured in resonances, and migrate with the giant body to short-period orbits. To determine the possibility of this scenario, we have studied the dynamics of a disk of protoplanetary embryos and the formation of terrestrial planets during the migration of a Jupiter-like planet around an M star. Results suggest that unless the terrestrial planet was also formed at large distances and carried to its close-in resonant orbit by the giant planet, it is unlikely for this object to form in small orbits. We present the details of our simulations and discuss the implication of the results for the origin of the terrestrial planet.
On the Rayleigh–Taylor Instability in Presence of a Background Shear

In this note we revisit the classical subject of the Rayleigh–Taylor instability in presence of an incompressible background shear flow. We derive a formula for the essential spectral radius of the evolution group generated by the linearization near the steady state and reveal that the velocity variations neutralize shortwave instabilities. The formula is a direct generalization of the result of Hwang and Guo (Arch Ration Mech Anal 167(3):235–253, (2003). Furthermore, we construct a class of steady states which posses unstable discrete spectrum with neutral essential spectrum. The technique involves the WKB analysis of the evolution equation and contains novel compactness criterion for pseudo-differential operators on unbounded domains.
The Surface Density Profile of the Galactic Disk from the Terminal Velocity Curve

The mass distribution of the Galactic disk is constructed from the terminal velocity curve and the mass discrepancy–acceleration relation. Mass models numerically quantifying the detailed surface density profiles are tabulated. For R0=8 kpc, the models have stellar mass 5<M*<6×10 10 M, scale length 2.0Rd 2.9 kpc, LSR circular velocity 222Θ0233 km s 1 - , and solar circle stellar surface density 34Σd(R0) 61 M pc 2  . The present interarm location of the solar neighborhood may have a somewhat lower stellar surface density than average for the solar circle. The Milky Way appears to be a normal spiral galaxy that obeys scaling relations like the Tully–Fisher relation, the size–mass relation, and the disk maximality–surface brightness relation. The stellar disk is maximal, and the spiral arms are massive. The bumps and wiggles in the terminal velocity curve correspond to known spiral features (e.g., the Centaurus arm is a ∼50% overdensity). The rotation curve switches between positive and negative over scales of hundreds of parsecs. The rms amplitude dV dR 14 km s kpc 21 2 1 1 ∣∣ a n» -- , implying that commonly neglected terms in the Jeans equations may be nonnegligible. The spherically averaged local dark matter density is ρ0,DM≈0.009 M pc 3  (0.34 GeV cm 3 - ). Adiabatic compression of the dark matter halo may help reconcile the Milky Way with the c–V200 relation expected in ΛCDM while also helping to mitigate the too-big-to-fail problem, but it remains difficult to reconcile the inner bulge/bar-dominated region with a cuspy halo. We note that NGC 3521 is a near twin to the Milky Way, having a similar luminosity, scale length, and rotation curve.
CHANDRA DETECTION OF EXTENDED X-RAY EMISSION FROM THE RECURRENT NOVA RS OPHIUCHI

Radio, infrared, and optical observations of the 2006 eruption of the symbiotic recurrent nova RS Ophiuchi showed that the explosion produced non-spherical ejecta. Some of this ejected material was in the form of bipolar jets to the east and west of the central source. Here we describe X-ray observations taken with the Chandra X-ray Observatory one and a half years after the beginning of the outburst that reveal narrow, extended structure with a position angle of approximately 300 deg. (east of north). Although the orientation of the extended feature in the X-ray image is consistent with the readout direction of the CCD detector, extensive testing suggests that the feature is not an artifact. Assuming it is not an instrumental effect, the extended X-ray structure shows hot plasma stretching more than 1900 AU from the central binary (taking a distance of 1.6 kpc). The X-ray emission is elongated in the northwest direction-in line with the extended infrared emission and some minor features in the published radio image. It is less consistent with the orientation of the radio jets and the main bipolar optical structure. Most of the photons in the extended X-ray structure have energies of less than 0.8 keV. Ifmore » the extended X-ray feature was produced when the nova explosion occurred, then its 1.''2 length as of 2007 August implies that it expanded at an average rate of more than 2 mas day{sup -1}, which corresponds to a flow speed of greater than 6000 km s{sup -1} (days/1.6 kpc) in the plane of the sky. This expansion rate is similar to the earliest measured expansion rates for the radio jets.« less
Enhancing spatial and textual analysis with EUPEG: An extensible and unified platform for evaluating geoparsers

A rich amount of geographic information exists in unstructured texts, such as Web pages, social media posts, housing advertisements, and historical archives. Geoparsers are useful tools that extract structured geographic information from unstructured texts, thereby enabling spatial analysis on textual data. While a number of geoparsers were developed, they were tested on different datasets using different metrics. Consequently, it is difficult to compare existing geoparsers or to compare a new geoparser with existing ones. In recent years, researchers created open and annotated corpora for testing geoparsers. While these corpora are extremely valuable, much effort is still needed for a researcher to prepare these datasets and deploy geoparsers for comparative experiments. This paper presents EUPEG: an Extensible and Unified Platform for Evaluating Geoparsers. EUPEG is an open source and Web based benchmarking platform which hosts a majority of open corpora, geoparsers, and performance metrics reported in the literature. It enables direct comparison of the hosted geoparsers, and a new geoparser can be connected to EUPEG and compared with other geoparsers. The main objective of EUPEG is to reduce the time and effort that researchers have to spend in preparing datasets and baselines, thereby increasing the efficiency and effectiveness of comparative experiments.
Titanium contacts to graphene: process-induced variability in electronic and thermal transport

Contact resistance (R C) is a major limiting factor in the performance of graphene devices. R C is sensitive to the quality of the interface and the composition of the contact, which are affected by the graphene transfer process and contact deposition conditions. In this work, a linear correlation is observed between the composition of Ti contacts, characterized by x-ray photoelectron spectroscopy, and the Ti/graphene contact resistance measured by the transfer length method. We find that contact composition is tunable via deposition rate and base pressure. Reactor base pressure is found to effect the resultant contact resistance. The effect of contact deposition conditions on thermal transport measured by time-domain thermoreflectance is also reported. Interfaces with higher oxide composition appear to result in a lower thermal boundary conductance. Possible origins of this thermal boundary conductance change with oxide composition are discussed.
DIS on a large nucleus in AdS/CFT

We calculate the total cross section for deep inelastic scattering (DIS) on a nucleus at high energy for a strongly coupled = 4 super Yang-Mills theory using AdS/CFT correspondence. In analogy to the small coupling case we argue that at high energy the total DIS cross section is related to the expectation value of the Wilson loop formed by the quark-antiquark dipole. We model the nucleus by a metric of a shock wave in AdS5. We then calculate the expectation value of the Wilson loop by finding the extrema of the Nambu-Goto action for an open string attached to the quark and antiquark lines of the loop in the background of an AdS5 shock wave. We find three extrema of the Nambu-Goto action: the string coordinates at the extrema are complex-valued and are given by three different branches of the solution of a cubic equation. The physically meaningful solutions for the total DIS cross section are given either by the only branch with a purely imaginary string coordinate in the bulk or by a superposition of the two other branches. For both solutions we obtain the forward scattering amplitude N for the quark dipole-nucleus scattering. We study the onset of unitarity with increasing center-of-mass energy and transverse size of the dipole: we observe that for both solutions the saturation scale, while energy-dependent at lower energies, at very high energy becomes independent of energy/Bjorken-x. The saturation scale depends very strongly on the atomic number of the nucleus as Qs ~ A1/3.
Black Sun: Ocular Invisibility of Relativistic Luminous Astrophysical Bodies

Considered as a gedanken experiment are the conditions under which the relativistic Doppler shifting of visible electromagnetic radiation to beyond the human ocular range could reduce the incident radiance of the source, and render a luminous astrophysical body (LAB) invisible to a naked eye. This paper determines the proper distance as a function of relativistic velocity at which a luminous object attains ocular invisibility.
Quantum-critical Pairing with Varying Exponents

We analyze the onset temperature Tp for the pairing in cuprate superconductors at small doping, when tendency towards antiferromagnetism is strong. We consider the model of Moon and Sachdev (MS), which assumes that electron and hole pockets survive in a paramagnetic phase. Within this model, the pairing between fermions is mediated by a gauge boson, whose propagator remains massless in a paramagnet. We relate the MS model to a generic γ-model of quantum-critical pairing with the pairing kernel \(\lambda(\Omega_{n})\propto1/\Omega^{\gamma}_{n}\). We show that, over some range of parameters, the MS model is equivalent to γ=1/3-model (λ(Ω)∝Ω−1/3). We find, however, that the parameter range where this analogy works is bounded on both ends. At larger deviations from a magnetic phase, the MS model becomes equivalent to γ model with varying γ>1/3, whose value depends on the distance to a magnetic transition and approaches γ=1 deep in a paramagnetic phase. Very near the transition, the MS model becomes equivalent to γ model with varying γ<1/3. Right at the magnetic QCP, the MS model is equivalent to the model with λ(Ωn)∝log Ωn, which is the model for color superconductivity. Using this analogy, we verify the formula for Tc derived for color superconductivity.
How Important is the Dark Matter Halo for Black Hole Growth

In this paper, we examine whether the properties of central black holes in galactic nuclei correlate with their host dark matter halos. We analyze the entire sample of galaxies where black hole mass, velocity dispersion σ, and asymptotic circular velocity Vc have all been measured. We fit M BH-σ and M BH-Vc to a power law, and find that in both relationships the scatter and slope are similar. This model-independent analysis suggests that although the black hole masses are not uniquely determined by dark matter halo mass, when considered for the current sample as a whole, the M BH-Vc correlation may be as strong (or as weak) as M BH-σ. Although the data are sparse, there appears to be more scatter in the correlation for both σ and Vc at the low-mass end. This is not unexpected given our current understanding of galaxy and black hole assembly. In fact, there are several compelling reasons that account for this: (1) supermassive black hole (SMBH) formation is likely less efficient in low-mass galaxies with large angular momentum content, (2) SMBH growth is less efficient in low-mass disk galaxies that have not experienced major mergers, and (3) dynamical effects, such as gravitational recoil, increase scatter preferentially at the low-mass end. Therefore, the recent observational claim of the absence of central SMBHs in bulgeless, low-mass galaxies, or deviations from the correlations defined by high-mass black holes in large galaxies today is, in fact, predicated by current models of black hole growth. We show how this arises as a direct consequence of the coupling between dark matter halos and central black holes at the earliest epochs.
Hidden multiscale order in the primes

We study the {pair correlations between} prime numbers in an interval $M \leq p \leq M + L$ with $M \rightarrow \infty$, $L/M \rightarrow \beta > 0$. By analyzing the \emph{structure factor}, we prove, conditionally on the {Hardy-Littlewood conjecture on prime pairs}, that the primes are characterized by unanticipated multiscale order. Specifically, their limiting structure factor is that of a union of an infinite number of periodic systems and is characterized by dense set of Dirac delta functions. Primes in dyadic intervals are the first examples of what we call {\it effectively limit-periodic} point configurations. This behavior implies anomalously suppressed density fluctuations compared to uncorrelated (Poisson) systems at large length scales, which is now known as hyperuniformity. Using a scalar order metric $\tau$ calculated from the structure factor, we identify a transition between the order exhibited when $L$ is comparable to $M$ and the uncorrelated behavior when $L$ is only logarithmic in $M$. Our analysis for the structure factor leads to an algorithm to reconstruct primes in a dyadic interval with high accuracy.
Orbital Stability of Exomoons and Submoons with Applications to Kepler 1625b-I

An intriguing question in the context of dynamics arises: Could a moon possess a moon itself? Such a configuration does not exist in the Solar System, although this may be possible in theory. Kollmeier et al. (2019) determined the critical size of a satellite necessary to host a long-lived sub-satellite, or submoon. However, the orbital constraints for these submoons to exist are still undetermined. Domingos et al. (2006) indicated that moons are stable out to a fraction of the host planet Hill radius $R_{H,p}$, which in turn depends on the eccentricity of its host's orbit. Motivated by this, we simulate a system of exomoons and submoons for $10^5$ planetary orbits, while considering many initial orbital phases to obtain the critical semimajor axis in terms of $R_{H,p}$ or the hosts satellite's Hill radius $R_{H,sat}$, respectively. We find that, assuming circular coplanar orbits, the stability limit for exomoons is 0.40 $R_{H,p}$ and for a submoon is 0.33 $R_{H,sat}$. Additionally, we discuss the observational feasibility of detecting these sub-satellites through photometric, radial velocity, or direct imaging observations using the Neptunes-sized exomoon candidates Kepler 1625b-I (Teachey et al. 2018) and identify how stability can shape the identification of future candidates.
Continuum modelling and simulation of granular flows through their many phases

We propose and numerically implement a constitutive framework for granular media that allows the material to traverse through its many common phases during the flow process. When dense, the material is treated as a pressure-sensitive elasto-viscoplastic solid obeying a yield criterion and a plastic flow rule given by the inertial rheology of granular materials. When the free volume exceeds a critical level, the material is deemed to separate and is treated as disconnected, stress-free media. A material point method (MPM) procedure is written for the simulation of this model and many demonstrations are provided in different geometries, which highlight the ability of the numerical model to handle transitions through dense and disconnected states. By using the MPM framework, extremely large strains and nonlinear deformations, which are common in granular flows, are representable. The method is verified numerically and its physical predictions are validated against many known experimental phenomena, such as Beverloo’s scaling in silo flows, jointed power-law scaling of the run-out distance in granular-column-collapse problems, and various known behaviours in inclined chute flows.
Constraining Jet Theories Using Nova Outbursts

It is commonly accepted that jets have not been observed in cataclysmic variables (CVs) so far. This absence was recently explained by their low mass transfer rates compared with objects with jets. A mass accretion limit for jets in CVs was proposed to be ~ 10-7 to 10-6 M☉ yr-1. There was, however, a report of evidence of jets in V1494 Aql, the second nova that erupted in Aquila in 1999. In this work, we estimate the mass transfer rate of this system around the reported event and show that it is consistent with the above theoretical limit for jets. We further propose that the X-ray flare that was observed in this object may be connected with a jet as well. The appearance of jets in novae is actually expected, since during the early decline from outburst some are like supersoft X-ray sources, in which jets have been found. The detection of jets in novae also fits the suggestion that in addition to the presence of an accretion disk, a hot central source is required for the formation of jets. The observations of jets during the transition phase in V1494 Aql can be regarded as evidence of the early existence of the accretion disk in the system. This conclusion supports our previous suggestion for a link between the transition phase in novae and the reestablishment of the accretion disk. We further speculate that jets may be restricted to transient novae. If our ideas are confirmed, jets should be common in transient novae and may be formed several times during the transition phase and perhaps even long after it ends. In classical novae jets may be launched and observed in real time. As binary systems, these objects are easy to study. Novae may, therefore, be key systems in understanding the formation and evolution of jets and ideal targets to test and constrain jet theories. Adding novae to the classes of systems showing jets should be very exciting and rewarding.
Exposition to Staggered Multi-Field Inflation

I investigate multi-field inflationary models with fields that decay during inflation, leading to staggered inflation. This feature is natural in many models motivated by string theory, for instance if inflatons are related to interbrane distances and the branes start to annihilate during inflation. A short exposition to an analytic framework is provided, enabling the computation of leading order corrections toobservables, i.e. the scalar spectral index.
Time-Series Anomaly Detection Service at Microsoft

Large companies need to monitor various metrics (for example, Page Views and Revenue) of their applications and services in real time. At Microsoft, we develop a time-series anomaly detection service which helps customers to monitor the time-series continuously and alert for potential incidents on time. In this paper, we introduce the pipeline and algorithm of our anomaly detection service, which is designed to be accurate, efficient and general. The pipeline consists of three major modules, including data ingestion, experimentation platform and online compute. To tackle the problem of time-series anomaly detection, we propose a novel algorithm based on Spectral Residual (SR) and Convolutional Neural Network (CNN). Our work is the first attempt to borrow the SR model from visual saliency detection domain to time-series anomaly detection. Moreover, we innovatively combine SR and CNN together to improve the performance of SR model. Our approach achieves superior experimental results compared with state-of-the-art baselines on both public datasets and Microsoft production data.
The Andromeda galaxy's most important merger about 2 billion years ago as M32's likely progenitor

Although the proximity of the Andromeda galaxy (M31) offers an opportunity to understand how mergers affect galaxies1, uncertainty remains about M31’s most important mergers. Previous studies focused individually on the giant stellar stream2 or the impact of M32 on M31’s disk3,4, thereby suggesting many substantial satellite interactions5. Yet models of M31’s disk heating6 and the similarity between the stellar populations of different tidal substructures in M31’s outskirts7 both suggested a single large merger. M31’s stellar halo (its outer low-surface-brightness regions) is built up from the tidal debris of satellites5 and provides information about its important mergers8. Here we use cosmological models of galaxy formation9,10 to show that M31’s massive11 and metal-rich12 stellar halo, containing intermediate-age stars7, dramatically narrows the range of allowed interactions, requiring a single dominant merger with a large galaxy (with stellar mass about 2.5 × 1010 solar masses, M☉ the third largest member of the Local Group) about 2 billion years (Gyr) ago. This single event explains many observations that were previously considered separately: M31’s compact and metal-rich satellite M3213 is likely to be the stripped core of the disrupted galaxy, its rotating inner stellar halo14 contains most of the merger debris, and the giant stellar stream15 is likely to have been thrown out during the merger. This interaction may explain M31’s global burst of star formation about 2 Gyr ago16 in which approximately a fifth of its stars were formed. Moreover, M31’s disk and bulge were already in place, suggesting that mergers of this magnitude need not dramatically affect galaxy structure.
Momentum‐space instantons and maximally localized flat‐band topological Hamiltonians

Recently, two-dimensional band insulators with a topologically nontrivial (almost) flat band in which integer and fractional quantum Hall effect can be realized without an orbital magnetic field have been studied extensively. Realizing a topological flat band generally requires longer range hoppings in a lattice Hamiltonian. It is natural to ask what is the minimal hopping range required. In this letter, we prove that the mean hopping range of the flat-band Hamiltonian with Chern number C_1 and total number of bands N has a universal lower bound of √4│C_1│/πN Furthermore, for the Hamiltonians that reach this lower bound, the Bloch wavefunctions of the topological flat band are instanton solutions of a CP^(N-1)equation image non-linear σ model on the Brillouin zone torus, which are elliptic functions up to a normalization factor.
Information-Theoretic Considerations Concerning the Origin of Life

Research investigating the origins of life usually either focuses on exploring possible life-bearing chemistries in the pre-biotic Earth, or else on synthetic approaches. Comparatively little work has explored fundamental issues concerning the spontaneous emergence of life using only concepts (such as information and evolution) that are divorced from any particular chemistry. Here, I advocate studying the probability of spontaneous molecular self-replication as a function of the information contained in the replicator, and the environmental conditions that might enable this emergence. I show (under certain simplifying assumptions) that the probability to discover a self-replicator by chance depends exponentially on the relative rate of formation of the monomers. If the rate at which monomers are formed is somewhat similar to the rate at which they would occur in a self-replicating polymer, the likelihood to discover such a replicator by chance is increased by many orders of magnitude. I document such an increase in searches for a self-replicator within the digital life system avida.
Relative anomaly in ( 1 + 1 )d rational conformal field theory

We study 't Hooft anomalies of symmetry-enriched rational conformal field theories (RCFT) in (1+1)d. Such anomalies determine whether a theory can be realized in a truly (1+1)d system with on-site symmetry, or on the edge of a (2+1)d symmetry-protected topological phase. RCFTs with the identical symmetry actions on their chiral algebras may have different 't Hooft anomalies due to additional symmetry charges on local primary operators. To compute the relative anomaly, we establish a precise correspondence between (1+1)d nonchiral RCFTs and (2+1)d doubled symmetry-enriched topological (SET) phases with a choice of a symmetric gapped boundary. Based on these results we derive a general formula for the relative 't Hooft anomaly in terms of algebraic data that characterizes the SET phase and its boundary.
Subbundles of maximal degree

Let E be a generic vector bundle of rank r and degree d on a generic curve of genus g. If r'd-rd'=r'(r-r')(g-1), the number of subbundles E' of E of rank r' and degree d' is finite. We present a new method to compute the number of such E' that consists in degenerating the curve to a reducible curve. We obtain very explicit formulae for r'=1 (Oxbury's Theorem) and also in the case r=4, r'=2.
On the flow of states under $T\overline{T}$

We study the $T\overline{T}$ deformation of two dimensional quantum field theories from a Hamiltonian point of view, focusing on aspects of the theory in Lorentzian signature. Our starting point is a simple rewriting of the spatial integral of the $T\overline{T}$ operator, which directly implies the deformed energy spectrum of the theory. Using this rewriting, we then derive flow equations for various quantities in the deformed theory, such as energy eigenstates, operators, and correlation functions. On the plane, we find that the deformation merely has the effect of implementing successive canonical/Bogoliubov transformations along the flow. This leads us to define a class of non-local, 'dressed' operators (including a dressed stress tensor) which satisfy the same commutation relations as in the undeformed theory. This further implies that on the plane, the deformed theory retains its symmetry algebra, including conformal symmetry, if the original theory is a CFT. On the cylinder the $T\overline{T}$ deformation is much more non-trivial, but even so, correlation functions of certain dressed operators are integral transforms of the original ones. Finally, we propose a tensor network interpretation of our results in the context of AdS/CFT.
The Discovery Potential of Space-Based Gravitational Wave Astronomy

A space-based interferometer operating in the previously unexplored mHz gravitational band has tremendous discovery potential. If history is any guide, the opening of a new spectral band will lead to the discovery of entirely new sources and phenomena.
Classification Of Uniform Flag Triangulations Of The Boundary Of The Full Root Polytope Of Type A

The full root polytope of type A is the convex hull of all pairwise differences of the standard basis vectors which we represent by forward and backward arrows. We completely classify all flag triangulations of this polytope that are uniform in the sense that the edges may be described as a function of the relative order of the indices of the four basis vectors involved. These fifteen triangulations fall naturally into three classes: three in the lex class, three in the revlex class and nine in the Simion class. We also consider a refined face count where we distinguish between forward and backward arrows. We prove the refined face counts only depend on the class of the triangulations. The refined face generating functions are expressed in terms of the Catalan and Delannoy generating functions and the modified Bessel function of the first kind.
Consistent estimation of the max-flow problem: Towards unsupervised image segmentation.

Advances in the image-based diagnostics of complex biological and manufacturing processes have brought unsupervised image segmentation to the forefront of enabling automated, on the fly decision making. However, most existing unsupervised segmentation approaches are either computationally complex or require manual parameter selection (e.g., flow capacities in max-flow/min-cut segmentation). In this work, we present a fully unsupervised segmentation approach using a continuous max-flow formulation over the image domain while optimally estimating the flow parameters from the image characteristics. More specifically, we show that the maximum a posteriori estimate of the image labels can be formulated as a continuous max-flow problem given the flow capacities are known. The flow capacities are then iteratively obtained by employing a novel Markov random field prior over the image domain. We present theoretical results to establish the posterior consistency of the flow capacities. We compare the performance of our approach using brain tumor image segmentation, defect identification in additively manufactured components using electron microscopic images, and segmentation of multiple real-world images. Comparative results with several state-of-the-art supervised as well as unsupervised methods suggest that the present method performs statistically similar to the supervised methods, but results in more than 90% improvement in the Dice score when compared to the state-of-the-art unsupervised methods.
The Michigan Infrared Test Thermal ELT N-band (MITTEN) cryostat

We introduce the Michigan Infrared Test Thermal ELT N-band (MITTEN) Cryostat, a new facility for testing infrared detectors with a focus on mid-infrared (MIR) wavelengths (8-13 microns). New generations of large format, deep well, fast readout MIR detectors are now becoming available to the astronomical community. As one example, Teledyne Imaging Sensors (TIS) has introduced a long-wave Mercury-Cadmium-Telluride (MCT) array, GeoSnap, with high quantum efficiency (< 65 %) and improved noise properties compared to previous generation Si:As blocked impurity band (BIB) detectors. GeoSnap promises improved sensitivities, and efficiencies, for future background-limited MIR instruments, in particular with future extremely large telescopes (ELTs). We describe our new test facility suitable for measuring characteristics of these detectors, such as read noise, dark current, linearity, gain, pixel operability, quantum efficiency, and point source imaging performance relative to a background scene, as well as multiple point sources of differing contrast. MITTEN has an internal light source, and soon an accompanying filter wheel and aperture plate, reimaged onto the detector using an Offner relay. The baseline temperature of the cryostat interior is maintained is < 40 K and the optical bench maintains a temperature of 16 K using a two-stage pulse-tube cryocooler package from Cryomech. No measurable background radiation from the cryostat interior has yet been detected.
Development and external validation of a prognostic tool for COVID-19 critical disease.

Author(s): Chow, Daniel S; Glavis-Bloom, Justin; Soun, Jennifer E; Weinberg, Brent; Loveless, Theresa Berens; Xie, Xiaohui; Mutasa, Simukayi; Monuki, Edwin; Park, Jung In; Bota, Daniela; Wu, Jie; Thompson, Leslie; Boden-Albala, Bernadette; Khan, Saahir; Amin, Alpesh N; Chang, Peter D | Abstract: AbstractBackgroundThe rapid spread of coronavirus disease 2019 (COVID-19) revealed significant constraints in critical care capacity. In anticipation of subsequent waves, reliable prediction of disease severity is essential for critical care capacity management and may enable earlier targeted interventions to improve patient outcomes. The purpose of this study is to develop and externally validate a prognostic model/clinical tool for predicting COVID-19 critical disease at presentation to medical care.MethodsThis is a retrospective study of a prognostic model for the prediction of COVID-19 critical disease where critical disease was defined as ICU admission, ventilation, and/or death. The derivation cohort was used to develop a multivariable logistic regression model. Covariates included patient comorbidities, presenting vital signs, and laboratory values. Model performance was assessed on the validation cohort by concordance statistics. The model was developed with consecutive patients with COVID-19 who presented to University of California Irvine Medical Center in Orange County, California. External validation was performed with a random sample of patients with COVID-19 at Emory Healthcare in Atlanta, Georgia.ResultsOf a total 3208 patients tested in the derivation cohort, 9% (299/3028) were positive for COVID-19. Clinical data including past medical history and presenting laboratory values were available for 29% (87/299) of patients (median age, 48 years [range, 21-88 years]; 64% [36/55] male). The most common comorbidities included obesity (37%, 31/87), hypertension (37%, 32/87), and diabetes (24%, 24/87). Critical disease was present in 24% (21/87). After backward stepwise selection, the following factors were associated with greatest increased risk of critical disease: number of comorbidities, body mass index, respiratory rate, white blood cell count, % lymphocytes, serum creatinine, lactate dehydrogenase, high sensitivity troponin I, ferritin, procalcitonin, and C-reactive protein. Of a total of 40 patients in the validation cohort (median age, 60 years [range, 27-88 years]; 55% [22/40] male), critical disease was present in 65% (26/40). Model discrimination in the validation cohort was high (concordance statistic: 0.94, 95% confidence interval 0.87-1.01). A web-based tool was developed to enable clinicians to input patient data and view likelihood of critical disease.Conclusions and RelevanceWe present a model which accurately predicted COVID-19 critical disease risk using comorbidities and presenting vital signs and laboratory values, on derivation and validation cohorts from two different institutions. If further validated on additional cohorts of patients, this model/clinical tool may provide useful prognostication of critical care needs.
Sub-linear Memory Sketches for Near Neighbor Search on Streaming Data

We present the first sublinear memory sketch that can be queried to find the nearest neighbors in a dataset. Our online sketching algorithm compresses an N element dataset to a sketch of size $O(N^b \log^3 N)$ in $O(N^{(b+1)} \log^3 N)$ time, where $b < 1$. This sketch can correctly report the nearest neighbors of any query that satisfies a stability condition parameterized by $b$. We achieve sublinear memory performance on stable queries by combining recent advances in locality sensitive hash (LSH)-based estimators, online kernel density estimation, and compressed sensing. Our theoretical results shed new light on the memory-accuracy tradeoff for nearest neighbor search, and our sketch, which consists entirely of short integer arrays, has a variety of attractive features in practice. We evaluate the memory-recall tradeoff of our method on a friend recommendation task in the Google Plus social media network. We obtain orders of magnitude better compression than the random projection based alternative while retaining the ability to report the nearest neighbors of practical queries.