cssi/SciSciGPT-SciSciNet huggingface dataset:
Extensions with the approximation and cover properties have no new large cardinals

If an extension Vbar of V satisfies the delta approximation and cover properties for classes and V is a class in Vbar, then every suitably closed embedding j:Vbar to Nbar in Vbar with critical point above delta restricts to an embedding j|V:V to N amenable to the ground model V. In such extensions, therefore, there are no new large cardinals above delta. This result extends work in math.LO/9808011.
Self-Imitation Learning via Generalized Lower Bound Q-learning

Self-imitation learning motivated by lower-bound Q-learning is a novel and effective approach for off-policy learning. In this work, we propose a n-step lower bound which generalizes the original return-based lower-bound Q-learning, and introduce a new family of self-imitation learning algorithms. To provide a formal motivation for the potential performance gains provided by self-imitation learning, we show that n-step lower bound Q-learning achieves a trade-off between fixed point bias and contraction rate, drawing close connections to the popular uncorrected n-step Q-learning. We finally show that n-step lower bound Q-learning is a more robust alternative to return-based self-imitation learning and uncorrected n-step, over a wide range of continuous control benchmark tasks.
A New Way of Detecting Intergalactic Baryons

For each photon wave packet of extragalactic light, the dispersion by line-of-sight intergalactic plasma causes an increase in the envelope width and a chirp (drift) in the carrier frequency. It is shown that for continuous emission of many temporally overlapping wave packets with random epoch phases such as quasars in the radio band, this in turn leads to quasi-periodic variations in the intensity of the arriving light on timescales between the coherence time (defined as the reciprocal of the bandwidth of frequency selection, taken here as of order 0.01 GHz for radio observations) and the stretched envelope, with most of the fluctuation power on the latter scale which is typically in the millisecond range for intergalactic dispersion. Thus, by monitoring quasar light curves on such short scales, it should be possible to determine the line-of-sight plasma column along the many directions and distances to the various quasars, affording one a three-dimensional picture of the ionized baryons in the near universe.
Leveraging High Resolution Spectra to Understand Black Hole Spectra

For the past 17 years, both XMM-Newton and Chandra have brought the powerful combination of high spatial and spectral resolution to the study of black hole systems. Each of these attributes requires special consideration—in comparison to lower spatial resolution charge-coupled device (CCD)-quality spectra—when modeling observations obtained by these spacecraft. A good understanding of the high-resolution spectra is in fact required to model properly lower resolution CCD spectra, with the reflection grating spectrometer (RGS) instrument on XMM-Newton maintaining the highest “figure of merit” at soft X-ray energies for all missions flying or currently planned for the next decade. Thanks to its even higher spectral resolution, the use of Chandra high-energy transmission gratings (HETGs), albeit with longer integration times, allows for one to bring further clarity to RGS studies. A further promising route for continued studies is the combination of high spectral resolution at soft X-rays, via RGS and/or HETG, with contemporaneous broadband coverage extending to hard X-rays (e.g., NuSTAR or INTEGRAL spectra). Such studies offer special promise for answering fundamental questions about accretion in black hole systems; however, they have received only moderate consideration to date. This may be due in part to the difficulty of analyzing high-resolution spectra. In response, we must continue to develop software tools that make the analysis of high-resolution X-ray spectra more accessible to the wider astrophysics community.
EXACT AND ASYMPTOTICALLY ROBUST PERMUTATION TESTS

Given independent samples from $P$ and $Q$, two-sample permutation tests allow one to construct exact level tests when the null hypothesis is $P=Q$. On the other hand, when comparing or testing particular parameters $\theta$ of $P$ and $Q$, such as their means or medians, permutation tests need not be level $\alpha$, or even approximately level $\alpha$ in large samples. Under very weak assumptions for comparing estimators, we provide a general test procedure whereby the asymptotic validity of the permutation test holds while retaining the exact rejection probability $\alpha$ in finite samples when the underlying distributions are identical. The ideas are broadly applicable and special attention is given to the $k$-sample problem of comparing general parameters, whereby a permutation test is constructed which is exact level $\alpha$ under the hypothesis of identical distributions, but has asymptotic rejection probability $\alpha$ under the more general null hypothesis of equality of parameters. A Monte Carlo simulation study is performed as well. A quite general theory is possible based on a coupling construction, as well as a key contiguity argument for the multinomial and multivariate hypergeometric distributions.
K-stability of birationally superrigid Fano varieties

We prove that every birationally superrigid Fano variety whose alpha invariant is greater than (respectively no smaller than) (under mild assumptions) and that the moduli space (if it exists) of birationally superrigid Fano varieties is separated.
The Green Choice: Learning and Influencing Human Decisions on Shared Roads

Autonomous vehicles have the potential to increase the capacity of roads via platooning, even when human drivers and autonomous vehicles share roads. However, when users of a road network choose their routes selfishly, the resulting traffic configuration may be very inefficient. Because of this, we consider how to influence human decisions so as to decrease congestion on these roads. We consider a network of parallel roads with two modes of transportation: (i) human drivers who will choose the quickest route available to them, and (ii) ride hailing service which provides an array of autonomous vehicle ride options, each with different prices, to users. In this work, we seek to design these prices so that when autonomous service users choose from these options and human drivers selfishly choose their resulting routes, road usage is maximized and transit delay is minimized. To do so, we formalize a model of how autonomous service users make choices between routes with different price/delay values. Developing a preference-based algorithm to learn the preferences of the users, and using a vehicle flow model related to the Fundamental Diagram of Traffic, we formulate a planning optimization to maximize a social objective and demonstrate the benefit of the proposed routing and learning scheme.
A Note on background independence in noncommutative gauge theories, matrix model and tachyon condensation

Using the construction of D-branes with nonzero B field in the matrix model we give a physical interpretation of the known background independence in gauge theories on a noncommutative space. The background independent variables are identified as the degrees of freedom of the underlying matrix model. This clarifies and extends some recent results about the end point of tachyon condensation in D-branes with a B field. We also explain the freedom in the description which is parametrized by a two form Φ from the points of view of the noncommutative geometry on the worldvolume of the branes, and of the first quantized string theory.
A remark on Witten effect for QCD monopoles in matrix quantum mechanics

In a recent work3 we argued that a certain matrix quantum mechanics may describe 't Hooft's monopoles which emerge in QCD when the theory is projected to its maximal Abelian subgroup. In this letter we find further evidence which supports this interpretation. We study the theory with a nonzero theta-term. In this case, 't Hooft's QCD monopoles become dyons since they acquire electric charges due to the Witten effect. We calculate a potential between a dyon and an anti-dyon in the matrix quantum mechanics, and find that the attractive force between them grows as the theta angle increases.
Burgess bounds for short character sums evaluated at forms

We establish a Burgess bound for short multiplicative character sums in arbitrary dimensions, in which the character is evaluated at a homogeneous form that belongs to a very general class of “admissible” forms. This n-dimensional Burgess bound is nontrivial for sums over boxes of sidelength at least qβ, with β>1∕2−1∕(2(n+1)). This is the first Burgess bound that applies in all dimensions to generic forms of arbitrary degree. Our approach capitalizes on a recent stratification result for complete multiplicative character sums evaluated at rational functions, due to the second author.
Lyubeznik numbers for nonsingular projective varieties

In this paper, we determine completely the Lyubeznik numbers $\lambda_{i,j}(A)$ of the local ring $A$ at the vertex of the affine cone over a nonsingular projective variety $V$, where $V$ is defined over a field of characteristic zero, in terms of the dimensions of the algebraic de Rham cohomology spaces of $V$. In particular, we prove that these numbers are intrinsic numerical invariants of $V$, even though a priori their definition depends on an embedding into projective space. This provides supporting evidence for a positive answer to the question of embedding-independence for arbitrary varieties in characteristic zero, which is still open.
The Color-Dependent Frequency of XUV Disks In Low-Mass E/S0s

We identify a high frequency of Type 1 XUV disks, reflecting recent outer-disk star formation, in a sample of 31 E/S0s with stellar masses primarily below M ∗ ~ 4 × 10 10 M ⊙ . Our ~40% identification rate is roughly twice the 20% fraction reported for late-type galaxies. Intriguingly, in the dwarf mass regime (below M ∗ ~ 5 × 10 9 M ⊙ ) where gas fractions increase, Type 1 XUV disks occur in ~70% of red -sequence E/S0s but only ~20% of blue-sequence E/S0s, a population recently linked to active disk rebuilding, especially in the dwarf regime. Our statistics are preliminary, but could indicate that Type 1 XUV disks in dwarf E/S0s are primarily related to weak/inefficient outer-disk star formation rather than to star formation capable of driving substantial disk growth.
A Flaring Magnetar in FRB 121102

The persistent radio counterpart of FRB 121102 is estimated to have $N\sim 10^{52}$ particles, energy $E_N\sim 10^{48}$ erg, and size $R\sim 10^{17}$ cm. The source can be a nebula inflated and heated by an intermittent outflow from a magnetar --- a neutron star powered by its magnetic (rather than rotational) energy. The object is young and frequently liberating energy in magnetic flares driven by accelerated ambipolar diffusion in the neutron star core, feeding the nebula and producing bright millisecond bursts. The particle number in the nebula is consistent with ion ejecta from giant flares. The nebula may also contain the freeze-out of electron-positron pairs $N_\pm\sim 10^{51}$ created months after the neutron star birth; the same mechanism offers an explanation for $N_\pm$ in the Crab nebula. The persistent source around FRB 121102 is likely heated by magnetic dissipation and internal waves excited by the magnetar ejecta. The volumetric heating by waves explains the nebula's enormous efficiency in producing radio emission. The repeating radio bursts are suggested to occur much closer to the magnetar, whose flaring magnetosphere drives ultrarelativistic internal shocks into the magnetar wind. The shocks are mediated by Larmor rotation that forms a GHz maser with the observed ms duration. Furthermore, the flare ejecta can become charge-starved and then convert to electromagnetic waves.
Exactly Solvable Model for the Decay of Superdeformed Nuclei

The history and importance of superdeformation in nuclei is briefly discussed. A simple two-level model is then employed to obtain an elegant expression for the branching ratio for the decay via the E1 process in the normal-deformed band of superdeformed nuclei. From this expression, the spreading width Γ↓ for superdeformed decay is found to be determined completely by experimentally known quantities. The accuracy of the two-level approximation is verified by considering the effects of other normal-deformed states. Furthermore, by using a statistical model of the energy levels in the normal-deformed well, we can obtain a probabilistic expression for the tunneling matrix element V.
Comparing elliptic and toric hypersurface Calabi-Yau threefolds at large Hodge numbers

We compare the sets of Calabi-Yau threefolds with large Hodge numbers that are constructed using toric hypersurface methods with those can be constructed as elliptic fibrations using Weierstrass model techniques motivated by F-theory. There is a close correspondence between the structure of “tops” in the toric polytope construction and Tate form tunings of Weierstrass models for elliptic fibrations. We find that all of the Hodge number pairs (h1,1, h2,1) with h1,1 or h2,1 ≥ 240 that are associated with threefolds in the Kreuzer-Skarke database can be realized explicitly by generic or tuned Weierstrass/Tate models for elliptic fibrations over complex base surfaces. This includes a relatively small number of somewhat exotic constructions, including elliptic fibrations over non-toric bases, models with new Tate tunings that can give rise to exotic matter in the 6D F-theory picture, tunings of gauge groups over non-toric curves, tunings with very large Hodge number shifts and associated nonabelian gauge groups, and tuned Mordell-Weil sections associated with U(1) factors in the corresponding 6D theory.
Hydrodynamics of tandem flapping pectoral fins with varying stroke phase offsets

Low-speed maneuvering and station keeping capabilities for small unmanned underwater vehicles (UUVs) are of great interest to the maritime community and flapping fins provide a potential solution for achieving these capabilities. We show how phasing between tandem bio-inspired fins flapping at high stroke amplitudes, i.e. by leading or lagging the rear fin with respect to the front fin modulates its thrust production, leading-edge suction and the overall wake characteristics of the system using load cell thrust measurements, two-dimensional particle image velocimetry measurements and three-dimensional computational fluid dynamics simulations.
Hadron properties in nuclear medium and their impacts on observables

We discuss here hadrons in a nuclear medium in quark-meson coupling (QMC) model . The model has been extended and successfully applied to many problems . A detailed description of the Lagrangian density, the mean-field equations of motion, and the treatment of finite nuclei are given in Refs. . As examples, we show in Fig. 1 results for Ca nucleus in QMC , which bases on the quark structure of nucleon, or, nucleus.
Frequency comb from a microresonator with engineered spectrum.

We demonstrate that by varying the ratio between the linewidth and dispersion of a whispering gallery mode resonator we are able to control the number N of free spectral ranges separating the first generated comb sidebands from the pump. We observed combs with N = 19 and N = 1. For the comb with N = 1 we have achieved a span of over 200 nm using a 0.4 mm MgF2 resonator pumped with 50 mW at 1560 nm. This pump power is a factor of 10 lower than previously reported for combs with comparable bandwidth.
On the Nature of the Sources of the Cosmic Infrared Background

We discuss the interpretation of the cosmic infrared background (CIB) anisotropies detected by us recently in the Spitzer/IRAC-based measurements. The fluctuations are approximately isotropic on the sky, which is consistent with their cosmological origin. They remain after the removal of fairly faint intervening sources and must arise from a population that has a strong CIB clustering component with only a small shot-noise level. We discuss the constraints the data place on the luminosities, epochs, and mass-to-light ratios of the individual sources producing them. Assuming the concordance ΛCDM cosmology, the measurements imply that the luminous sources producing them lie at cosmic times <1 Gyr and were individually much brighter per unit mass than the present stellar populations.
Super Star Cluster Velocity Dispersions and Virial Masses in the M82 Nuclear Starburst

We use high-resolution near-infrared spectroscopy from Keck Observatory to measure the stellar velocity dispersions of 19 super star clusters (SSCs) in the nuclear starburst of M82. The clusters have ages on the order of 10 Myr, which is many times longer than the crossing times implied by their velocity dispersions and radii. We therefore apply the virial theorem to derive the kinematic mass for 15 of the SSCs. The SSCs have masses of 2 × 105 to 4 × 106 M☉, with a total population mass of 1.4 × 107 M☉. Comparison of the loci of the young M82 SSCs and old Milky Way globular clusters in a plot of radius versus velocity dispersion suggests that the SSCs are a population of potential globular clusters. We present the mass function for the SSCs and find a power-law fit with an index of γ = -1.91 ± 0.06. This result is nearly identical to the mass function of young SSCs in the Antennae galaxies.
Absolute uniqueness of phase retrieval with random illumination

Random illumination is proposed to enforce absolute uniqueness and resolve all types of ambiguity, trivial or nontrivial, in phase retrieval. Almost sure irreducibility is proved for any complex-valued object whose support set has rank 2. While the new irreducibility result can be viewed as a probabilistic version of the classical result by Bruck, Sodin and Hayes, it provides a novel perspective and an effective method for phase retrieval. In particular, almost sure uniqueness, up to a global phase, is proved for complex-valued objects under general two-point conditions. Under a tight sector constraint absolute uniqueness is proved to hold with probability exponentially close to unity as the object sparsity increases. Under a magnitude constraint with random amplitude illumination, uniqueness modulo global phase is proved to hold with probability exponentially close to unity as object sparsity increases. For general complex-valued objects without any constraint, almost sure uniqueness up to global phase is established with two sets of Fourier magnitude data under two independent illuminations. Numerical experiments suggest that random illumination essentially alleviates most, if not all, numerical problems commonly associated with the standard phasing algorithms. (Some figures may appear in colour only in the online journal)
Detecting Replay Attacks Using Multi-Channel Audio: A Neural Network-Based Method

With the rapidly growing number of security-sensitive systems that use voice as the primary input, it becomes increasingly important to address these systems’ potential vulnerability to replay attacks. Previous efforts to address this concern have focused primarily on single-channel audio. In this paper, we introduce a novel neural network-based replay attack detection model that further leverages spatial information of multi-channel audio and is able to significantly improve the replay attack detection performance.
Thermodynamic Constraints on the Size Distributions of Tropical Clouds

Tropical convective clouds evolve over a wide range of temporal and spatial scales, and this makes them difficult to simulate numerically. Here, we propose that their statistical properties can be derived within a simplified time-independent co-ordinate system of cloud number $n$, saturated static energy $h^\star$, and cloud perimeter $\lambda$. Under the constraint that circulations around cloud edge compete for buoyant energy and air, we show that the product of cloud number and cloud perimeter $n\lambda$ is invariant with $\lambda$ and that cloud number follows a negative exponential with respect to cloud-edge deviations of $h^\star$ from the mean. Overall, the summed perimeter of all clouds scales as the square root of the atmospheric static stability, which suggests that the complexity of cloud field structures can be viewed statistically as an emergent property of atmospheric bulk thermodynamics. Analytically derived conclusions are compared with a detailed tropical cloud field simulation and found generally to agree to within $<$13%. For the sake of developing hypotheses about cloud temporal evolution that are testable in high resolution simulations, the shapes of tropical cloud perimeter distributions are predicted to be invariant as climate warms, although with a modest increase in total cloud amount.
Charge-To-Spin Conversion Efficiency in Ferromagnetic Nanowires by Spin Torque Ferromagnetic Resonance: Reconciling Lineshape and Linewidth Analysis Methods

Spin orbit torques are of great interest for switching the magnetization direction in nanostructures, moving skyrmions and exciting spin waves. The standard method of determining their efficiency is by spin torque ferromagnetic resonance (ST-FMR), a technique that involves analyzing the resonance linewidth or lineshape. On microstuctures these two analysis methods are quite consistent. Here we present ST-FMR results on permalloy (${\mathrm{Ni}}_{80}{\mathrm{Fe}}_{20}$) nanowires---with widths varying from $150$ to 800 nm---that show that the standard model used to analyze the resonance linewidth and lineshape give different results; the efficiency appears greatly enhanced in nanowires when the lineshape method is used. A ST-FMR model that properly accounts for the sample shape is presented and shows much better consistency between the two methods. Micromagnetic simulations are used to verify the model. These results and the more accurate nanowire model presented are of importance for characterizing and optimizing charge-to-spin conversion efficiencies in nanostructures.
0103-72.6: A new oxygen-rich supernova remnant in the small magellanic cloud

0103-72.6, the second brightest X-ray supernova remnant (SNR) in the Small Magellanic Cloud (SMC), has been observed with the Chandra X-Ray Observatory. Our Chandra observation unambiguously resolves the X-ray emission into a nearly complete, remarkably circular shell surrounding bright clumpy emission in the center of the remnant. The observed X-ray spectrum for the central region is evidently dominated by emission from reverse-shock-heated metal-rich ejecta. Elemental abundances in this ejecta material are particularly enhanced in oxygen and neon, while less prominent in the heavier elements Si, S, and Fe. We thus propose that 0103-72.6 is a new "oxygen-rich" SNR, making it only the second member of the class in the SMC. The outer shell is the limb-brightened soft X-ray emission from the swept-up SMC interstellar medium. The presence of O-rich ejecta and the SNR's location within an H II region attest to a massive star core-collapse origin for 0103-72.6. The elemental abundance ratios derived from the ejecta suggest an ~18 M☉ progenitor star.
Non-equilibrium three-dimensional boundary layers at moderate Reynolds numbers

Non-equilibrium wall turbulence with mean-flow three-dimensionality is ubiquitous in geophysical and engineering flows. Under these conditions, turbulence may experience a counter-intuitive depletion of the turbulent stresses, which has important implications for modelling and control. Yet, current turbulence theories have been established mainly for statistically two-dimensional equilibrium flows and are unable to predict the reduction in the Reynolds stress magnitude. In the present work, we propose a multiscale model that captures the response of non-equilibrium wall-bounded turbulence under the imposition of three-dimensional strain. The analysis is performed via direct numerical simulation of transient three-dimensional turbulent channels subjected to a sudden lateral pressure gradient at friction Reynolds numbers up to 1000. We show that the flow regimes and scaling properties of the Reynolds stress are consistent with a model comprising momentum-carrying eddies with sizes and time scales proportional to their distance to the wall. We further demonstrate that the reduction in Reynolds stress follows a spatially and temporally self-similar evolution caused by the relative horizontal displacement between the core of the momentum-carrying eddies and the flow layer underneath. Inspection of the flow energetics reveals that this mechanism is associated with lower levels of pressure–strain correlation, which ultimately inhibits the generation of Reynolds stress, consistent with previous works. Finally, we assess the ability of the state-of-the-art wall-modelled large-eddy simulation to predict non-equilibrium three-dimensional flows.
A CO J = 1–0 survey of common optical/uv absorption sightlines

Context. Comparison of optical/uv absorption line data with high-resolution profiles of mm-wave CO emission provides complementary information on the absorbing gas, as toward ζOph. Over the past thirty years a wealth of observations of CO and other molecules in optical/uv absorption in diffuse clouds has accumulated for which no comparable CO emission line data exist. Aims. To acquire mm-wave J = 1-0 CO emission line profiles toward a substantial sample of commonly-studied optical/uv absorption line targets and to compare with the properties of the absorbing gas, especially the predicted emission line strengths. Methods. Using the ARO 12 m telescope, we observed mm-wavelength J = 1-0 CO emission with spectral resolution R ≈ 3 x 10 6 and spatial resolution 1' toward a sample of 110 lines of sight previously studied in optical/uv absorption lines of CO, H 2 , CH, etc. Results. Interstellar CO emission was detected along 65 of the 110 lines of sight surveyed and there is a general superabundance of CO emission given the distribution of galactic latitudes in the survey sample. Much of the emission is optically thick or very intense and must emanate from dark clouds or warm dense gas near HII regions. Conclusions. Judging from the statistical superabundance of CO emission, seen also in the total line of sight reddening, the OB star optical/uv absorption line targets must be physically associated with the large quantities of neutral gas whose CO emission was detected, in which case they are probably influencing the absorbing gas by heating and/or photoionizing it. This explains why CO/H 2 and 12 CO/ 13 CO ratios differ somewhat between uv and mm-wave absorption line studies. Because the lines of sight have been preselected to have Av ≤ 1 mag, relatively little of the associated material actually occults the targets, making it difficult for CO emission line observations to isolate the foreground gas contribution.
Exact results in softly broken supersymmetric models

Abstract We show how recent exact results in supersymmetric theories can be extended to models which include explicit soft supersymmetry breaking terms. We thus derive new exact results for non-supersymmetric models.
The Albedo Distribution of Near Earth Asteroids

The cryogenic Wide-field Infrared Survey Explorer (WISE) mission in 2010 was extremely sensitive to asteroids and not biased against detecting dark objects. The albedos of 428 near Earth asteroids (NEAs) observed by WISE during its fully cryogenic mission can be fit quite well by a three parameter function that is the sum of two Rayleigh distributions. The Rayleigh distribution is zero for negative values, and follows f(x) = x exp[-x^2/2σ^2)]/σ^2 for positive x. The peak value is at x = σ, so the position and width are tied together. The three parameters are the fraction of the objects in the dark population, the position of the dark peak, and the position of the brighter peak. We find that 25.3% of the NEAs observed by WISE are in a very dark population peaking at p_V = 0.030, while the other 74.7% of the NEAs seen by WISE are in a moderately dark population peaking at p_V = 0.168. A consequence of this bimodal distribution is that the congressional mandate to find 90% of all NEAs larger than 140 m diameter cannot be satisfied by surveying to H = 22 mag, since a 140 m diameter asteroid at the very dark peak has H = 23.7 mag, and more than 10% of NEAs are darker than p_V = 0.03.
Closed-form shock solutions

It is shown here that a subset of the implicit analytical shock solutions discovered by Becker and by Johnson can be inverted, yielding several exact closed-form solutions of the one-dimensional compressible Navier–Stokes equations for an ideal gas. For a constant dynamic viscosity and thermal conductivity, and at particular values of the shock Mach number, the velocity can be expressed in terms of a polynomial root. For a constant kinematic viscosity, independent of Mach number, the velocity can be expressed in terms of a hyperbolic tangent function. The remaining fluid variables are related to the velocity through simple algebraic expressions. The solutions derived here make excellent verification tests for numerical algorithms, since no source terms in the evolution equations are approximated, and the closed-form expressions are straightforward to implement. The solutions are also of some academic interest as they may provide insight into the nonlinear character of the Navier–Stokes equations and may stimulate further analytical developments.
The Muon g − 2 experiment at Fermilab

The current ~ 3.5σ discrepancy between the experimental measurement and theoretical prediction of the muon magnetic anomaly, a µ , stands as a potential indication of the existence of new physics. The Muon g − 2 experiment at Fermilab is set to measure a µ with a four-fold improvement in the uncertainty with respect to previous experiment, with an aim to determine whether the g − 2 discrepancy is well established. The experiment recently completed its first physics run and a summer programme of essential upgrades, before continuing on with its experimental programme. The Run-1 data alone are expected to yield a statistical uncertainty of 350 ppb and the publication of the first result is expected in late-2019.
Detectability of intermediate-mass black holes in multiband gravitational wave astronomy

The direct measurement of gravitational waves is a powerful tool for surveying the population of black holes across the universe. While LIGO has detected black holes as heavy as ~50 M⊙ (ref. 1), there is not yet unambiguous evidence of black holes in the intermediate mass range of 102–5 M⊙. Recent electromagnetic observations have hinted towards the existence of intermediate-mass black holes (IMBHs)2–4; however, their masses remain poorly constrained. Here we argue that multiband observations by space- and ground-based gravitational wave detectors5,6 will be able to survey a broad population of IMBHs at cosmological distances. By utilizing general relativistic simulations of merging black holes7 and state-of-the-art gravitational waveform models8, we classify three distinct populations of binaries with IMBHs and discuss what can be observed about each. Multiband observations involving the upgraded LIGO detector9 and the proposed space-mission LISA10 would detect the inspiral, merger and ring-down of IMBH binaries out to redshift ≈ 2, pushing out to redshift ≈ 5 if next-generation ground-based detectors11,12 are operational at the same time. To facilitate studies of multiband IMBH sources, we provide analytic relations for the maximum redshift of multiband detectability, as a function of black hole mass, for various detector combinations. Our study paves the way for future work on what can be learned from IMBH observations in the era of multiband gravitational wave astronomy. Multi-frequency observations by the upgraded LIGO/Virgo and the proposed LISA space gravitational wave detector will be used to detect intermediate-mass black hole binaries in their inspiral, merger and ring-down phases out to cosmological distances.
Systematic Investigations of the Free Fermionic Heterotic String Gauge Group Statistics:. Layer 1 Results

Using software under development at Baylor University, we explicitly construct all layer 1 gauge, weakly coupled free fermionic heterotic string models up to order 22 in four large spacetime dimensions. The gauge models consist primarily of gauge content making a systematic construction process efficient. We present an overview of the model building procedure, redundancies in the process, methods used to reduce such redundancies and statistics regarding the occurrence of various combinations of gauge group factors and GUT groups. Statistics for both and models are presented.
A METHOD FOR SETTING UPPER LIMITS TO THE EXTRAGALACTIC BACKGROUND LIGHT WITH FERMI-LAT AND TeV OBSERVATIONS OF BLAZARS

We propose a method for setting upper limits to the extragalactic background light (EBL). Our method uses simultaneous Fermi-LAT and ground-based TeV observations of blazars and is based on the assumption that the intrinsic spectral energy distribution (SED) of TeV blazars lies below the extrapolation of the Fermi-LAT SED from GeV to TeV energies. By extrapolating the Fermi-LAT spectrum, which for TeV blazars is practically unattenuated by photon-photon pair production with EBL photons, a firm upper limit on the intrinsic SED at TeV energies is provided. The ratio of the extrapolated spectrum to the observed TeV spectrum provides upper limits to the optical depth for the propagation of the TeV photons due to pair production on the EBL, which in turn sets firm upper limits to EBL models. We demonstrate our method using simultaneous observations from Fermi-LAT and ground-based TeV telescopes of the blazars PKS 2155-304 and 1ES 1218+304, and show that high EBL density models are disfavored. We also discuss how our method can be optimized and how Fermi and X-ray monitoring observations of TeV blazars can guide future TeV campaigns, leading to potentially much stronger constraints on EBL models.
Discovery of a new black hole transient within 100'' (400 PC) of M31*

We identified a new X-ray transient CXOM31 004252.457+411631.17 (T13) in M31 during a 2013 June Chandra observation. This system is particularly exciting because it is located within 100'' of M31*; it is thought that this region of the bulge is sufficiently dense to form X-ray binaries dynamically, but only systems with black hole accretors and/or short periods are expected to survive. A follow-up XMM-Newton observation yielded a soft spectrum, well described by a 0.39 ± 0.02 keV disk blackbody; applying this model to the Chandra observation yielded an observed 0.3-10 keV luminosity peak of 6.2 ± 0.6× 1037 erg s–1 (4.7× 1036 erg s–1 in the 2.0-10 keV band). Observing with Hubble Space Telescope/Advanced Camera for Surveys did not reveal an optical counterpart, but allowed us to place an upper limit of B > 26.9, corresponding to an absolute V band magnitude >2.0. From the 2-10 keV luminosity and absolute V magnitude, we estimate an orbital period <5 h from an empirical relation. Fitting a disk blackbody + blackbody model allows us to reject a neutron star accretor at a 14σ level.
Synthetic Topological Qubits in Conventional Bilayer Quantum Hall Systems

Topological qubits can process and store quantum information. A new theory proposes that topological qubits can be synthesized in experimentally well-established conventional bilayer fractional quantum Hall states.
A Refined Threshold Theorem for (1 + 2)-Dimensional Wave Maps into Surfaces

The recently established threshold theorem for energy critical wave maps states that wave maps with energy less than that of the ground state (i.e., a minimal energy nontrivial harmonic map) are globally regular and scatter on \({\mathbb{R}^{1+2}}\). In this note we give a refinement of this theorem when the target is a closed orientable surface, by taking into account an additional invariant of the problem, namely the topological degree. We show that the sharp energy threshold for global regularity and scattering is in fact twice the energy of the ground state for wave maps with degree zero, whereas wave maps with nonzero degree necessarily have at least the energy of the ground state. We also give a discussion on the formulation of a refined threshold conjecture for the energy critical SU(2) Yang–Mills equation on \({\mathbb{R}^{1+4}}\).
Unambiguous separation of the inverse spin Hall and anomalous Nernst effects within a ferromagnetic metal using the spin Seebeck effect

The longitudinal spin Seebeck effect is measured on the ferromagnetic insulator Fe3O4 with the ferromagnetic metal Co0.2Fe0.6B0.2 (CoFeB) as the spin detector. By using a non-magnetic spacer material between the two materials (Ti), it is possible to decouple the two ferromagnetic materials and directly observe pure spin flow from Fe3O4 into CoFeB. It is shown that in a single ferromagnetic metal, the inverse spin Hall effect (ISHE) and anomalous Nernst effect (ANE) can occur simultaneously with opposite polarity. Using this and the large difference in the coercive fields between the two magnets, it is possible to unambiguously separate the contributions of the spin Seebeck effect from the ANE and observe the degree to which each effect contributes to the total response. These experiments show conclusively that the ISHE and ANE in CoFeB are separate phenomena with different origins and can coexist in the same material with opposite response to a thermal gradient.
On risk bounds in isotonic and other shape restricted regression problems

We consider the problem of estimating an unknown $\theta\in\mathbb{R}^{n}$ from noisy observations under the constraint that $\theta$ belongs to certain convex polyhedral cones in $\mathbb{R}^{n}$. Under this setting, we prove bounds for the risk of the least squares estimator (LSE). The obtained risk bound behaves differently depending on the true sequence $\theta$ which highlights the adaptive behavior of $\theta$. As special cases of our general result, we derive risk bounds for the LSE in univariate isotonic and convex regression. We study the risk bound in isotonic regression in greater detail: we show that the isotonic LSE converges at a whole range of rates from $\log n/n$ (when $\theta$ is constant) to $n^{-2/3}$ (when $\theta$ is uniformly increasing in a certain sense). We argue that the bound presents a benchmark for the risk of any estimator in isotonic regression by proving nonasymptotic local minimax lower bounds. We prove an analogue of our bound for model misspecification where the true $\theta$ is not necessarily nondecreasing.
THE CIRCUMSTELLAR DISK MASS DISTRIBUTION IN THE ORION TRAPEZIUM CLUSTER

We present the results of a submillimeter interferometric survey of circumstellar disks in the Trapezium cluster of Orion. We observed the 880 μm continuum emission from 55 disks using the Submillimeter Array,1The Submillimeter Array is a joint project between the Submillimeter Astrophysical Observatory and the Academica Sinica Institute of Astronomy and Astrophysics and is funded by the Smithsonian Institution and the Academica Sinica. and detected 28 disks above 3σ significance with fluxes between 6 and 70 mJy and rms noise between 0.7 and 5.3 mJy. Dust masses and upper limits are derived from the submillimeter excess above free-free emission extrapolated from longer wavelength observations. Above our completeness limit of 0.0084 M ☉, the disk mass distribution is similar to that of Class II disks in Taurus-Auriga and ρ Ophiuchus but is truncated at 0.04 M ☉. We show that the disk mass and radius distributions are consistent with the formation of Trapezium cluster disks ~1 Myr ago and subsequent photoevaporation by the ultraviolet radiation field from θ1 Ori C. The fraction of disks that contain a minimum mass solar nebula within 60 AU radius is estimated to be 11%-13% in both Taurus and the Trapezium cluster, which suggests the potential for forming Solar Systems is not compromised in this massive star-forming region.
Longitudinal dynamics and tomography in the Tevatron

Motivated by the desire to understand the longitudinal effects of beam-beam forces, we study the longitudinal dynamics of protons and anti-protons at injection energy and top energy in the Tevatron. Multi-turn data of the longitudinal profiles are captured to reveal information about frequencies of oscillation, and changes in the bunch distributions. Tomographic reconstruction is used to create phase space maps which are subsequently used to find the momentum distributions. Changes in these distributions for both proton and anti-proton beams are also followed through the operational cycle. We report on the details of interesting dynamics during injection, acceleration and collisions.
A Cut-Free Sequent Calculus for Defeasible Erotetic Inferences

In recent years, the effort to formalize erotetic inferences—i.e., inferences to and from questions—has become a central concern for those working in erotetic logic. However, few have sought to formulate a proof theory for these inferences. To fill this lacuna, we construct a calculus for (classes of) sequents that are sound and complete for two species of erotetic inferences studied by Inferential Erotetic Logic (IEL): erotetic evocation and erotetic implication. While an effort has been made to axiomatize the former in a sequent system, there is currently no proof theory for the latter. Moreover, the extant axiomatization of erotetic evocation fails to capture its defeasible character and provides no rules for introducing or eliminating question-forming operators. In contrast, our calculus encodes defeasibility conditions on sequents and provides rules governing the introduction and elimination of erotetic formulas. We demonstrate that an elimination theorem holds for a version of the cut rule that applies to both declarative and erotetic formulas and that the rules for the axiomatic account of question evocation in IEL are admissible in our system.
Scalability of VM provisioning systems

Virtual machines and virtualized hardware have been around for over half a century. The commoditization of the x86 platform and its rapidly growing hardware capabilities have led to recent exponential growth in the use of virtualization both in the enterprise and high performance computing (HPC). The startup time of a virtualized environment is a key performance metric for high performance computing in which the runtime of any individual task is typically much shorter than the lifetime of a virtualized service in an enterprise context. In this paper, a methodology for accurately measuring the startup performance on an HPC system is described. The startup performance overhead of three of the most mature, widely deployed cloud management frameworks (OpenStack, OpenNebula, and Eucalyptus) is measured to determine their suitability for workloads typically seen in an HPC environment. A 10x performance difference is observed between the fastest (Eucalyptus) and the slowest (OpenNebula) framework. This time difference is primarily due to delays in waiting on networking in the cloud-init portion of the startup. The methodology and measurements presented should facilitate the optimization of startup across a variety of virtualization environments.
A Suzaku X-ray Study of the Particle Acceleration Processes in the Relativistic Jet of Blazar Mrk 421

We report on the findings of a 364 ks observation of the BL LAC object Mrk 421 with the X-ray observatory Suzaku. The analysis in this paper uses fluxes and hardness ratios (HRs) in the broad energy range from 0.5 keV to 30 keV. During the course of the observation, the 0.5-30 keV flux decreased by a factor of ~2 and was accompanied by several large flares occurring on timescales of a few hours. We find that fitting a broken power model to spectra from isolated epochs during the observation describes the data well. Different flares exhibit different spectral and HR evolutions. The cumulative observational evidence indicates that the particle acceleration mechanism in the Mrk 421 jet produces electron energy distributions with a modest range of spectral indices and maximum energies. We argue that the short-timescale X-ray spectral variability in the flares can be attributed mostly to intrinsic changes in the acceleration process, dominating other influences such as fluctuations in the Doppler beaming factor, or radiative cooling in or outside the acceleration zone.
Wavelet Denoising of Radio Observations of Rotating Radio Transients (RRATs): Improved Timing Parameters for Eight RRATs

Rotating radio transients (RRATs) are sporadically emitting pulsars detectable only through searches for single pulses. While over 100 RRATs have been detected, only a small fraction (roughly 20%) have phase-connected timing solutions, which are critical for determining how they relate to other neutron star populations. Detecting more pulses in order to achieve solutions is key to understanding their physical nature. Astronomical signals collected by radio telescopes contain noise from many sources, making the detection of weak pulses difficult. Applying a denoising method to raw time series prior to performing a single-pulse search typically leads to a more accurate estimation of their times of arrival (TOAs). Taking into account some features of RRAT pulses and noise, we present a denoising method based on wavelet data analysis, an image-processing technique. Assuming that the spin period of an RRAT is known, we estimate the frequency spectrum components contributing to the composition of RRAT pulses. This allows us to suppress the noise, which contributes to other frequencies. We apply the wavelet denoising method including selective wavelet reconstruction and wavelet shrinkage to the de-dispersed time series of eight RRATs with existing timing solutions. The signal-to-noise ratio (S/N) of most pulses are improved after wavelet denoising. Compared to the conventional approach, we measure 12%–69% more TOAs for the eight RRATs. The new timing solutions for the eight RRATs show 16%–90% smaller estimation error of most parameters. Thus, we conclude that wavelet analysis is an effective tool for denoising RRATs signal.
Modeling Shocks Detected by Voyager 1 in the Local Interstellar Medium

The magnetometer (MAG) on Voyager 1 (V1) has been sampling the interstellar magnetic field (ISMF) since 2012 August. The V1 MAG observations have shown draped ISMF in the very local interstellar medium disturbed occasionally by significant enhancements in magnetic field strength. Using a three-dimensional, data-driven, multi-fluid model, we investigated these magnetic field enhancements beyond the heliopause that are supposedly associated with solar transients. To introduce time-dependent effects at the inner boundary at 1 au, we used daily averages of the solar wind parameters from the OMNI data set. The model ISMF strength, direction, and proton number density are compared with V1 data beyond the heliopause. The model reproduced the large-scale fluctuations between 2012.652 and 2016.652, including major events around 2012.9 and 2014.6. The model also predicts shocks arriving at V1 around 2017.395 and 2019.502. Another model driven by OMNI data with interplanetary coronal mass ejections (ICMEs) removed at the inner boundary suggests that ICMEs may play a significant role in the propagation of shocks into the interstellar medium.