cssi/SciSciGPT-SciSciNet huggingface dataset:
The utmost rigidity property for quadratic foliations on $$\mathbb {P}^2$$ with an invariant line

In this work, we consider holomorphic foliations of degree two on the complex projective plane \(\mathbb {P}^2\) having an invariant line. In a suitable choice of affine coordinates, these foliations are induced by a quadratic vector field over the affine part in such a way that the invariant line corresponds to the line at infinity. We say that two such foliations are topologically equivalent provided there exists a homeomorphism of \(\mathbb {P}^2\) which brings the leaves of one foliation onto the leaves of the other and preserves orientation both on the ambient space and on the leaves. The main result of this paper is that in the generic case, two such foliations may be topologically equivalent if and only if they are analytically equivalent. In fact, it is shown that the analytic conjugacy class of the holonomy group of the invariant line is the modulus of both topological and analytic classification. We obtain as a corollary that two generic orbitally topologically equivalent quadratic vector fields on \(\mathbb {C}^2\) must be orbitally affine equivalent. This result improves, in the case of quadratic foliations, a well-known result by Ilyashenko that claims that two generic and topologically equivalent foliations with an invariant line at infinity are affine equivalent, provided they are close enough in the space of foliations and the linking homeomorphism is close enough to the identity map of \(\mathbb {P}^2\).
Coupling an ensemble of electrons on superfluid helium to a superconducting circuit

A new quantum device uses a superconducting circuit to monitor a 2D gas of electrons floating on the surface of superfluid helium.
Genus-two trisections are standard

We show that the only closed 4–manifolds admitting genus-two trisections are S2 × S2 and connected sums of S1 × S3, ℂℙ2 and ℂℙ¯2 with two summands. Moreover, each of these manifolds admits a unique genus-two trisection up to diffeomorphism. The proof relies heavily on the combinatorics of genus-two Heegaard diagrams of S3. As a corollary, we classify tunnel number one links with an integral cosmetic Dehn surgery.
BENEFITS OF GROUND-BASED PHOTOMETRIC FOLLOW-UP FOR TRANSITING EXTRASOLAR PLANETS DISCOVERED WITH KEPLER AND CoRoT

Currently, over 40 transiting planets have been discovered by ground-based photometric surveys, and space-based missions such as Kepler and CoRoT are expected to detect hundreds more. Follow-up photometric observations from the ground will play an important role in constraining both orbital and physical parameters for newly discovered planets, especially those with small radii (Rp 4R ⊕) and/or intermediate-to-long orbital periods (P 30 days). Here, we simulate transit light curves (LCs) from Kepler-like photometry and ground-based observations in the near-infrared (NIR) to determine how jointly modeling space-based and ground-based LCs can improve measurements of the transit duration and planet-star radius ratio. We find that adding observations of at least one ground-based transit to space-based observations can significantly improve the accuracy for measuring the transit duration and planet-star radius ratio of small planets (Rp 4R ⊕) in long-period (~1 year) orbits, largely thanks to the reduced effect of limb darkening in the NIR. We also demonstrate that multiple ground-based observations are needed to gain a substantial improvement in the measurement accuracy for small planets with short orbital periods (~3 days). Finally, we consider the role that higher ground-based precisions will play in constraining parameter measurements for typical Kepler targets. Our results can help inform the priorities of transit follow-up programs (including both primary and secondary transit of planets discovered with Kepler and CoRoT), leading to improved constraints for transit durations, planet sizes, and orbital eccentricities.
Veneziano Amplitude of Vasiliev Theory

We compute the four-point function of scalar operators in CFTs with weakly broken higher spin symmetry at arbitrary ’t Hooft coupling. We use the known three-point functions in these theories, the Lorentzian OPE inversion formula and crossing to fix the result up to the addition of three functions of the cross ratios. These are given by contact Witten diagrams in AdS and manifest non-analyticity of the OPE data in spin. We use Schwinger-Dyson equations to provide strong numerical evidence that such terms are absent in the large N Chern-Simons matter theories. The result is that the OPE data is analytic in spin up to J = 0.
Figuring out Art History

World population and the number of cultural artifacts are growing exponentially or faster, while cultural interaction approaches the fidelity of a global nervous system. Every day hundreds of millions of images are loaded into social networks by users all over the world. As this myriad of new artifacts veils the view into the past, like city lights covering the night sky, it is easy to forget that there is more than one Starry Night, the painting by Van Gogh. Like in ecology, where saving rare species may help us in treating disease, art and architectural history can reveal insights into the past, which may hold keys to our own future. With humanism under threat, facing the challenge of understanding the structure and dynamics of art and culture, both qualitatively and quantitatively, is more crucial now than it ever was. The purpose of this article is to provide perspective in the aim of figuring out the process of art history – not art history as a discipline, but the actual history of all made things, in the spirit of George Kubler and Marcel Duchamp. In other words, this article deals with the grand challenge of developing a systematic science of art and culture, no matter what, and no matter how.
Nucleons in two-flavor partially-quenched chiral perturbation theory

Abstract Properties of the proton and the neutron are explored in partially-quenched chiral perturbation theory with two non-degenerate light flavors. Masses, magnetic moments, matrix elements of isovector twist-2 operators and axial-vector currents are computed at the one-loop level in the chiral expansion.
Harmonic Analysis Approach to Gromov–Hausdorff Convergence for Noncommutative Tori

We show that the rotation algebras are limits of matrix algebras in a very strong sense of convergence for algebras with additional Lipschitz structure. Our results generalize to higher dimensional noncommutative tori and operator valued coefficients. In contrast to previous results by Rieffel, Li, Kerr, and Latremoliere, we use Lipschitz norms induced by the ‘carre du champ’ of certain natural dynamical systems, including the heat semigroup.
Genus-two mutant knots with the same dimension in knot Floer and Khovanov homologies

We exhibit an infinite family of knots with isomorphic knot Heegaard Floer homology. Each knot in this infinite family admits a nontrivial genus-two mutant which shares the same total dimension in both knot Floer homology and Khovanov homology. Each knot is distinguished from its genus-two mutant by both knot Floer homology and Khovanov homology as bigraded groups. Additionally, for both knot Heegaard Floer homology and Khovanov homology, the genus-two mutation interchanges the groups in i–gradings k and k .
Optimal modularity and memory capacity of neural reservoirs.

The neural network is a powerful computing framework that has been exploited by biological evolution and by humans for solving diverse problems. Although the computational capabilities of neural ne...
Invariant Solutions to the Strominger System on Complex Lie Groups and Their Quotients

Using canonical 1-parameter family of Hermitian connections on the tangent bundle, we provide invariant solutions to the Strominger system on certain complex Lie groups and their quotients. Both flat and non-flat cases are discussed in detail. This paper answers a question proposed by Andreas and Garcia-Fernandez in Comm Math Phys 332(3):1381–1383, 2014.
Reconnecting Magnetic Flux Tubes as a Source of In Situ Acceleration in Extragalactic Radio Sources

Many extended extragalactic radio sources require a local in situ acceleration mechanism for electrons, in part because the synchrotron lifetimes are shorter than the bulk travel time across the emitting regions. If the magnetic field in these sources is localized in flux tubes, reconnection may occur between regions of plasma β (ratio of particle to magnetic pressure) 1, even though β averaged over the plasma volume may be 1. Reconnection in low-β regions is most favorable to acceleration from reconnection shocks. The reconnection X-point regions may provide the injection electrons for their subsequent nonthermal shock acceleration to distributions reasonably consistent with observed spectra. Flux-tube reconnection might therefore be able to provide in situ acceleration required by large-scale jets and lobes.
THE NEUTRAL HYDROGEN BRIDGE BETWEEN M31 AND M33

The Green Bank Telescope has been used to search for 21 cm H I emission over a large area between the galaxies M31 and M33 in an attempt to confirm at 9.'1 angular resolution the detection by Braun and Thilker of a very extensive neutral gas 'bridge' between the two systems at the level N{sub HI} Almost-Equal-To 10{sup 17} cm{sup -2}. We detect H I emission at several locations up to 120 kpc in projected distance from M31, at least half the distance to M33, with velocities similar to that of the galaxies, confirming the essence of the Braun and Thilker discovery. The H I does not appear to be associated with the extraplanar high-velocity clouds of either galaxy. In two places we measure N{sub HI} > 3 Multiplication-Sign 10{sup 18} cm{sup -2}, indicative of concentrations of H I with {approx}10{sup 5} M{sub Sun} on scales {approx}< 2 kpc, but over most of the field we have only 5{sigma} upper limits of N{sub HI} {<=} 1.4 Multiplication-Sign 10{sup 18} cm{sup -2}. In very deep measurements in two directions H I lines were detected at a few 10{sup 17} cm{sup -2}. The absence of emission at another location to a 5{sigma}more » limit N{sub HI} {<=} 1.5 Multiplication-Sign 10{sup 17} cm{sup -2} suggests that the H I bridge is either patchy or confined to within {approx}125 kpc of M31. The measurements also cover two of M31's dwarf galaxies, And II and And XV, but in neither case is there evidence for associated H I at the 5{sigma} level of 1.4 Multiplication-Sign 10{sup 4} M{sub Sun} for And II and 9.3 Multiplication-Sign 10{sup 3} M{sub Sun} for And XV.« less
Estimates for first-order homogeneous linear characteristic problems

An algebraic criterion that is sufficient to establish the existence of certain a priori estimates for the solution of first-order homogeneous linear characteristic problems is derived. Estimates of such kind ensure the stability of the solutions under small variations of the data. Characteristic problems that satisfy this criterion are, in a sense, manifestly well posed.
Chandra High Energy Transmission Grating Spectrum of AE Aquarii

The nova-like cataclysmic binary AE Aqr, which is currently understood to be a former supersoft X-ray binary and current magnetic propeller, was observed for over two binary orbits (78 ks) in 2005 August with the High-Energy Transmission Grating (HETG) on board the Chandra X-ray Observatory. The long, uninterrupted Chandra observation provides a wealth of details concerning the X-ray emission of AE Aqr, many of which are new and unique to the HETG. First, the X-ray spectrum is that of an optically thin multi-temperature thermal plasma; the X-ray emission lines are broad, with widths that increase with the line energy from σ ≈ 1 eV (510 km s–1) for O VIII to σ ≈ 5.5 eV (820 km s–1) for Si XIV; the X-ray spectrum is reasonably well fit by a plasma model with a Gaussian emission measure distribution that peaks at log T(K) = 7.16, has a width σ = 0.48, an Fe abundance equal to 0.44 times solar, and other metal (primarily Ne, Mg, and Si) abundances equal to 0.76 times solar; and for a distance d = 100 pc, the total emission measure EM = 8.0 × 1053 cm–3 and the 0.5-10 keV luminosity L X = 1.1 × 1031 erg s–1. Second, based on the f/(i + r) flux ratios of the forbidden (f), intercombination (i), and recombination (r) lines of the Heα triplets of N VI, O VII, and Ne IX measured by Itoh et al. in the XMM-Newton Reflection Grating Spectrometer spectrum and those of O VII, Ne IX, Mg XI, and Si XIII in the Chandra HETG spectrum, either the electron density of the plasma increases with temperature by over three orders of magnitude, from n e ≈ 6 × 1010 cm–3 for N VI [log T(K) ≈ 6] to n e ≈ 1 × 1014 cm–3 for Si XIII [log T(K) ≈ 7], and/or the plasma is significantly affected by photoexcitation. Third, the radial velocity of the X-ray emission lines varies on the white dwarf spin phase, with two oscillations per spin cycle and an amplitude K ≈ 160 km s–1. These results appear to be inconsistent with the recent models of Itoh et al., Ikhsanov, and Venter & Meintjes of an extended, low-density source of X-rays in AE Aqr, but instead support earlier models in which the dominant source of X-rays is of high density and/or in close proximity to the white dwarf.
A model of regulatory dynamics with threshold-type state-dependent delay

We model intracellular regulatory dynamics with threshold-type state-dependent delay and investigate the effect of the state-dependent diffusion time. A general model which is an extension of the classical differential equation models with constant or zero time delays is developed to study the stability of steady state, the occurrence and stability of periodic oscillations in regulatory dynamics. Using the method of multiple time scales, we compute the normal form of the general model and show that the state-dependent diffusion time may lead to both supercritical and subcritical Hopf bifurcations. Numerical simulations of the prototype model of Hes1 regulatory dynamics are given to illustrate the general results.
The Inverse Galois Problem for p-adic fields

We describe a method for counting the number of extensions of $\mathbb{Q}_p$ with a given Galois group $G$, founded upon the description of the absolute Galois group of $\mathbb{Q}_p$ due to Jannsen and Wingberg. Because this description is only known for odd $p$, our results do not apply to $\mathbb{Q}_2$. We report on the results of counting such extensions for $G$ of order up to $2000$ (except those divisible by $512$), for $p=3,5,7,11,13$. In particular, we highlight a relatively short list of minimal $G$ that do not arise as Galois groups. Motivated by this list, we prove two theorems about the inverse Galois problem for $\mathbb{Q}_p$: one giving a necessary condition for $G$ to be realizable over $\mathbb{Q}_p$ and the other giving a sufficient condition.
Wavelet representations and Fock space on positive matrices

Abstract We show that every biorthogonal wavelet determines a representation by operators on Hilbert space satisfying simple identities, which captures the established relationship between orthogonal wavelets and Cuntz-algebra representations in that special case. Each of these representations is shown to have tractable finite-dimensional co-invariant doubly cyclic subspaces. Further, motivated by these representations, we introduce a general Fock-space Hilbert space construction which yields creation operators containing the Cuntz–Toeplitz isometries as a special case.
Large area metalenses: design, characterization, and mass manufacturing.

Optical components, such as lenses, have traditionally been made in the bulk form by shaping glass or other transparent materials. Recent advances in metasurfaces provide a new basis for recasting optical components into thin, planar elements, having similar or better performance using arrays of subwavelength-spaced optical phase-shifters. The technology required to mass produce them dates back to the mid-1990s, when the feature sizes of semiconductor manufacturing became considerably denser than the wavelength of light, advancing in stride with Moore’s law. This provides the possibility of unifying two industries: semiconductor manufacturing and lens-making, whereby the same technology used to make computer chips is used to make optical components, such as lenses, based on metasurfaces. Using a scalable metasurface layout compression algorithm that exponentially reduces design file sizes (by 3 orders of magnitude for a centimeter diameter lens) and stepper photolithography, we show the design and fabrication of metasurface lenses (metalenses) with extremely large areas, up to centimeters in diameter and beyond. Using a single two-centimeter diameter near-infrared metalens less than a micron thick fabricated in this way, we experimentally implement the ideal thin lens equation, while demonstrating high-quality imaging and diffraction-limited focusing.
D4M 3.0: Extended database and language capabilities

The D4M tool was developed to address many of today's data needs. This tool is used by hundreds of researchers to perform complex analytics on unstructured data. Over the past few years, the D4M toolbox has evolved to support connectivity with a variety of new database engines, including SciDB. D4M-Graphulo provides the ability to do graph analytics in the Apache Accumulo database. Finally, an implementation using the Julia programming language is also now available. In this article, we describe some of our latest additions to the D4M toolbox and our upcoming D4M 3.0 release. We show through benchmarking and scaling results that we can achieve fast SciDB ingest using the D4M-SciDB connector, that using Graphulo can enable graph algorithms on scales that can be memory limited, and that the Julia implementation of D4M achieves comparable performance or exceeds that of the existing MATLAB® implementation.
SPH simulation of fuel drop impact on heated surfaces

Abstract The interaction of liquid drops and heated surfaces is of great importance in many applications. This paper describes a numerical method, based on smoothed particle hydrodynamics (SPH), for simulating n-heptane drop impact on a heated surface. The SPH method uses numerical Lagrangian particles, which obey the laws of fluid dynamics, to describe the fluid flows. By incorporating the Peng–Robinson equation of state, the present SPH method can directly simulate both the liquid and vapor phases and the phase change process between them. The numerical method was validated by two experiments on drop impact on heated surfaces at low impact velocities. The numerical method was then used to predict drop-wall interactions at various temperatures and velocities. The model was able to predict the different outcomes, such as rebound, spread, splash, breakup, and the Leidenfrost phenomenon, consistent with the physical understanding.
Binary asteroid encounters with terrestrial planets: Timescales and effects

Many asteroids that make close encounters with terrestrial planets are in a binary configuration. Here, we calculate the relevant encounter timescales and investigate the effects of encounters on a binary's mutual orbit. We use a combination of analytical and numerical approaches with a wide range of initial conditions. Our test cases include generic binaries with close, moderate, and wide separations, as well as seven well-characterized near-Earth binaries. We find that close approaches (<10 Earth radii) occur for almost all binaries on 1-10 million year timescales. At such distances, our results suggest substantial modifications to a binary's semimajor axis, eccentricity, and inclination, which we quantify. Encounters within 30 Earth radii typically occur on sub-million year timescales and significantly affect the wider binaries. Important processes in the lives of near-Earth binaries, such as tidal and radiative evolution, can be altered or stopped by planetary encounters.
COSMIC REIONIZATION ON COMPUTERS: THE FAINT END OF THE GALAXY LUMINOSITY FUNCTION

Using numerical cosmological simulations completed under the “Cosmic Reionization On Computers” project, I explore theoretical predictions for the faint end of the galaxy UV luminosity functions at $$z\gtrsim 6$$. A commonly used Schechter function approximation with the magnitude cut at $${M}_{{\rm{cut}}}\sim -13$$ provides a reasonable fit to the actual luminosity function of simulated galaxies. When the Schechter functional form is forced on the luminosity functions from the simulations, the magnitude cut $${M}_{{\rm{cut}}}$$ is found to vary between -12 and -14 with a mild redshift dependence. Here, an analytical model of reionization from Madau et al., as used by Robertson et al., provides a good description of the simulated results, which can be improved even further by adding two physically motivated modifications to the original Madau et al. equation.
IMAGING OF THE CCS 22.3 GHz EMISSION IN THE TAURUS MOLECULAR CLOUD COMPLEX

Thioxoethenylidene (CCS) is an abundant interstellar molecule and a good tracer of high density and evolutionary stage of dense molecular clouds. It is also a suitable candidate for Zeeman splitting observations for its high splitting factor and narrow thermal line widths. We report here Expanded Very Large Array 22.3 GHz observations of three dense molecular cores TMC-1, TMC-1C, and L1521B in the Taurus molecular cloud complex to image the CCS 21-10 transition. For all three sources, the clumpy CCS emission is most likely tracing the starless cores. However, these compact structures account for only ~1%-13% of the integrated emission detected in single-dish observations, indicating the presence of significant large-scale diffuse emission in favorable conditions for producing CCS.
Torsion points and isogenies on CM elliptic curves

Let $\mathcal{O}$ be an order in the imaginary quadratic field $K$. For positive integers $M \mid N$, we determine the least degree of an $\mathcal{O}$-CM point on the modular curve $X(M,N)_{/K(\zeta_M)}$ and also on the modular curve $X(M,N)_{/\mathbb{Q}(\zeta_M)}$: that is, we treat both the case in which the complex multiplication is rationally defined and the case in which we do not assume that the complex multiplication is rationally defined. To prove these results we establish several new theorems on rational cyclic isogenies of CM elliptic curves. In particular, we extend a result of Kwon that determines the set of positive integers $N$ for which there is an $\mathcal{O}$-CM elliptic curve $E$ admitting a cyclic, $\mathbb{Q}(j(E))$-rational $N$-isogeny.
VStore: A Data Store for Analytics on Large Videos

We present VStore, a data store for supporting fast, resource-efficient analytics over large archival videos. VStore manages video ingestion, storage, retrieval, and consumption. It controls video formats along the video data path. It is challenged by i) the huge combinatorial space of video format knobs; ii) the complex impacts of these knobs and their high profiling cost; iii) optimizing for multiple resource types. It explores an idea called backward derivation of configuration: in the opposite direction along the video data path, VStore passes the video quantity and quality expected by analytics backward to retrieval, to storage, and to ingestion. In this process, VStore derives an optimal set of video formats, optimizing for different resources in a progressive manner. VStore automatically derives large, complex configurations consisting of more than one hundred knobs over tens of video formats. In response to queries, VStore selects video formats catering to the executed operators and the target accuracy. It streams video data from disks through decoder to operators. It runs queries as fast as 362x of video realtime.
Genus Bounds for Harmonic Group Actions on Finite Graphs

This paper develops graph analogues of the genus bounds for the maximal size of an automorphism group of a compact Riemann surface of genus $g\ge 2$. Inspired by the work of M. Baker and S. Norine on harmonic morphisms between finite graphs, we motivate and define the notion of a harmonic group action. Denoting by M(g) the maximal size of such a harmonic group action on a graph of genus $g\ge 2$, we prove that $4(g-1)\le M(g)\le 6(g-1)$, and these bounds are sharp in the sense that both are attained for infinitely many values of g. Moreover, we show that the values $4(g-1)$ and $6(g-1)$ are the only values taken by the function $M(g)$.
A comparison between the metric dimension and zero forcing number of trees and unicyclic graphs

The metric dimension dim(G) of a graph G is the minimum number of vertices such that every vertex of G is uniquely determined by its vector of distances to the chosen vertices. The zero forcing number Z(G) of a graph G is the minimum cardinality of a set S of black vertices (whereas vertices in V(G)S are colored white) such that V(G) is turned black after finitely many applications of “the color-change rule”: a white vertex is converted black if it is the only white neighbor of a black vertex. We show that dim(T) ≤ Z(T) for a tree T, and that dim(G) ≤ Z(G)+1 if G is a unicyclic graph; along the way, we characterize trees T attaining dim(T) = Z(T). For a general graph G, we introduce the “cycle rank conjecture”. We conclude with a proof of dim(T) − 2 ≤ dim(T + e) ≤ dim(T) + 1 for $$e \in E\left( {\bar T} \right)$$ .
Developments in Topological Gravity

This note aims to provide an entree to two developments in two-dimensional topological gravity — that is, intersection theory on the moduli space of Riemann surfaces — that have not yet become well...
Untwisting information from Heegaard Floer homology

The unknotting number of a knot is the minimum number of crossings one must change to turn that knot into the unknot. We work with a generalization of the unknotting number due to Mathieu–Domergue, which we call the untwisting number. The p–untwisting number is the minimum number (over all diagrams of a knot) of full twists on at most 2p strands of a knot, with half of the strands oriented in each direction, necessary to transform that knot into the unknot. In previous work, we showed that the unknotting and untwisting numbers can be arbitrarily different. In this paper, we show that a common route for obstructing low unknotting number, the Montesinos trick, does not generalize to the untwisting number. However, we use a different approach to get conditions on the Heegaard Floer correction terms of the branched double cover of a knot with untwisting number one. This allows us to obstruct several 10– and 11–crossing knots from being unknotted by a single positive or negative twist. We also use the Ozsvath–Szabo τ invariant and the Rasmussen s invariant to differentiate between the p– and q–untwisting numbers for certain p,q > 1.
High distance bridge surfaces

Given integers b , c , g and n , we construct a manifold M containing a c –component link L so that there is a bridge surface † for .M;L/ of genus g that intersects L in 2b points and has distance at least n . More generally, given two possibly disconnected surfaces S and S 0 , each with some even number (possibly zero) of marked points, and integers b , c , g and n , we construct a compact, orientable manifold M with boundary S [S 0 such that M contains a c –component tangle T with a bridge surface † of genus g that separates @M into S and S 0 , jT \ †j D 2b and T intersects S and S 0 exactly in their marked points, and † has distance at least n .
STAR FORMATION FEEDBACK AND METAL-ENRICHMENT HISTORY OF THE INTERGALACTIC MEDIUM

Using the state-of-the-art cosmological hydrodynamic simulations of the standard cold dark matter model with star formation feedback strength normalized to match the observed star formation history of the universe at z= 0-6, we compute the metal-enrichment history of the intergalactic medium (IGM). Overall we show that galactic superwind (GSW) feedback from star formation can transport metals to the IGM and that the properties of simulated metal absorbers match current observations. The distance of influence of GSW from galaxies is typically limited to about { =} 10. Most C IV and O VI absorbers are located within shocked regions of elevated temperature (T {>=} 2 x 10{sup 4} K), overdensity ({delta} {>=} 10), and metallicity ([Z/Z{sub sun}] = [ - 2.5, - 0.5]), enclosed by double shocks propagating outward. O VI absorbers have typically higher metallicity, lower density, and higher temperature than C IV absorbers. For O VI absorbers, collisional ionization dominates over the entire redshift range z= 0-6, whereas for C IV absorbers the transition occurs at moderate redshift z {approx} 3 from collisionally dominated to photoionization dominated. We find that the observed column density distributions for C IV and O VI inmore » the range log N cm{sup 2}=12-15 are reasonably reproduced by the simulations. The evolution of mass densities contained in C IV and O VI lines, {Omega}{sub CIV} and {Omega}{sub OVI}, is also in good agreement with observations, which shows a near constancy at low redshifts and an exponential drop beyond redshift z= 3-4. For both C IV and O VI, most absorbers are transient and the amount of metals probed by C IV and O VI lines of column log N cm{sup 2}=12-15 is only {approx}2% of total metal density at any epoch. While gravitational shocks from large-scale structure formation dominate the energy budget (80%-90%) for turning about 50% of the IGM to the warm-hot intergalactic medium (WHIM) by z = 0, GSW feedback shocks are energetically dominant over gravitational shocks at z{>=}1-2. Most of the so-called missing metals at z= 2-3 are hidden in a warm-hot (T = 10{sup 4.5}-10{sup 7} K) gaseous phase, heated up by GSW feedback shocks. Their mass distribution is broadly peaked at {delta}=1-10 in the IGM, outside virialized halos. Approximately 37%, 46%, 10%, and 7% of the total metals at z = 0 are in stars, WHIM, X-ray gas, and cold gas, respectively; the distributions stand at 23%, 57%, 2%, and 18% and 14%, 51%, 4%, and 31% at z = 2 and z = 4, respectively.« less
Swept Source Lidar: simultaneous FMCW ranging and nonmechanical beam steering with a wideband swept source

Light detection and ranging (lidar) has long been used in various applications. Solid-state beam steering mechanisms are needed for robust lidar systems. Here we propose and demonstrate a lidar scheme called "Swept Source Lidar" that allows us to perform frequency-modulated continuous-wave (FMCW) ranging and nonmechanical beam steering simultaneously. Wavelength dispersive elements provide angular beam steering, while a laser frequency is continuously swept by a wideband swept source over its whole tuning bandwidth. Employing a tunable vertical-cavity surface-emitting laser and a 1-axis mechanical beam scanner, three-dimensional point cloud data has been obtained. Swept Source Lidar systems can be flexibly combined with various beam steering elements to realize full solid-state FMCW lidar systems.
Unsupervised Discovery of Implicit Gender Bias

Despite their prevalence in society, social biases are difficult to identify, primarily because human judgements in this domain can be unreliable. We take an unsupervised approach to identifying gender bias against women at a comment level and present a model that can surface text likely to contain bias. Our main challenge is forcing the model to focus on signs of implicit bias, rather than other artifacts in the data. Thus, our methodology involves reducing the influence of confounds through propensity matching and adversarial learning. Our analysis shows how biased comments directed towards female politicians contain mixed criticisms, while comments directed towards other female public figures focus on appearance and sexualization. Ultimately, our work offers a way to capture subtle biases in various domains without relying on subjective human judgements.
Searching for exoplanets using a microresonator astrocomb

Orbiting planets induce a weak radial velocity (RV) shift in the host star that provides a powerful method of planet detection. Importantly, the RV technique provides information about the exoplanet mass, which is unavailable with the complementary technique of transit photometry. However, RV detection of an Earth-like planet in the 'habitable zone'1 requires extreme spectroscopic precision that is only possible using a laser frequency comb (LFC)2. Conventional LFCs require complex filtering steps to be compatible with astronomical spectrographs, but a new chip-based microresonator device, the Kerr soliton microcomb3-8, is an ideal match for astronomical spectrograph resolution and can eliminate these filtering steps. Here, we demonstrate an atomic/molecular line-referenced soliton microcomb as a first in-the-field demonstration of microcombs for calibration of astronomical spectrographs. These devices can ultimately provide LFC systems that would occupy only a few cubic centimetres9,10, thereby greatly expanding implementation of these technologies into remote and mobile environments beyond the research lab.
Resolution of Nearly Mass Degenerate Higgs Bosons and Production of Black Hole Systems of Known Mass at a Muon Collider

The direct s-channel coupling to Higgs bosons is 40000 times greater for muons than electrons; the coupling goes as mass squared. High precision scanning of the lighter h0 and the higher mass H0 and A0 is thus possible with a muon collider. The H0 and A0 are expected to be nearly mass degenerate and to be CP even and odd, respectively. A muon collider could resolve the mass degeneracy and make CP measurements. The origin of CP violation in the K0 and B0 meson systems might lie in the the H0/A0 Higgs bosons. If large extra dimensions exist, black holes with lifetimes of ~ 10-26 seconds could be created and observed via Hawking radiation at the LHC. Unlike proton or electron colliders, muon colliders can produce black hole systems of known mass. This opens the possibilities of measuring quantum remnants, gravitons as missing energy, and scanning production turn on. Proton colliders are hampered by parton distributions and CLIC by beamstrahlung. The ILC lacks the energy reach.
Local bounds for $L^p$ norms of Maass forms in the level aspect

We apply techniques from harmonic analysis to study the Lp norms of Maass forms of varying level on a quaternion division algebra. Our first result gives a candidate for the local bound for the sup norm in terms of the level, which is new when the level is not squarefree. The second result is a bound for Lp norms in the level aspect that is analogous to Sogge’s theorem on Lp norms of Laplace eigenfunctions.
System identification in dynamical sampling

We consider the problem of spatiotemporal sampling in a discrete infinite dimensional spatially invariant evolutionary process x(n) = Anx to recover an unknown convolution operator A given by a filter a?l1(?)$a \in \ell ^{1}(\mathbb {Z})$ and an unknown initial state x modeled as a vector in l2(?)$\ell ^{2}(\mathbb {Z})$. Traditionally, under appropriate hypotheses, any x can be recovered from its samples on ?$\mathbb {Z}$ and A can be recovered by the classical techniques of deconvolution. In this paper, we will exploit the spatiotemporal correlation and propose a new sampling scheme to recover A and x that allows us to sample the evolving states x,Ax,? ,AN?1x on a sub-lattice of ?$\mathbb {Z}$, and thus achieve a spatiotemporal trade off. The spatiotemporal trade off is motivated by several industrial applications (Lu and Vetterli, 2249---2252, 2009). Specifically, we show that {x(m?),Ax(m?),?,AN?1x(m?):N?2m}$\{x(m\mathbb {Z}), Ax(m\mathbb {Z}), \cdots , A^{N-1}x(m\mathbb {Z}): N \geq 2m\}$ contains enough information to recover a typical "low pass filter" a and x almost surely, thus generalizing the idea of the finite dimensional case in Aldroubi and Krishtal, arXiv:1412.1538 (2014). In particular, we provide an algorithm based on a generalized Prony method for the case when both a and x are of finite impulse response and an upper bound of their support is known. We also perform a perturbation analysis based on the spectral properties of the operator A and initial state x, and verify the results by several numerical experiments. Finally, we provide several other numerical techniques to stabilize the proposed method, with some examples to demonstrate the improvement.
Density Estimation for Projected Exoplanet Quantities

Exoplanet searches using radial velocity (RV) and microlensing (ML) produce samples of "projected" mass and orbital radius, respectively. We present a new method for estimating the probability density distribution (density) of the unprojected quantity from such samples. For a sample of n data values, the method involves solving n simultaneous linear equations to determine the weights of delta functions for the raw, unsmoothed density of the unprojected quantity that cause the associated cumulative distribution function (CDF) of the projected quantity to exactly reproduce the empirical CDF of the sample at the locations of the n data values. We smooth the raw density using nonparametric kernel density estimation with a normal kernel of bandwidth σ. We calibrate the dependence of σ on n by Monte Carlo experiments performed on samples drawn from a theoretical density, in which the integrated square error is minimized. We scale this calibration to the ranges of real RV samples using the Normal Reference Rule. The resolution and amplitude accuracy of the estimated density improve with n. For typical RV and ML samples, we expect the fractional noise at the PDF peak to be approximately 80 n –log 2. For illustrations, we apply the new method to 67 RV values given a similar treatment by Jorissen et al. in 2001, and to the 308 RV values listed at exoplanets.org on 2010 October 20. In addition to analyzing observational results, our methods can be used to develop measurement requirements—particularly on the minimum sample size n—for future programs, such as the microlensing survey of Earth-like exoplanets recommended by the Astro 2010 committee.
Mixtures of g-Priors in Generalized Linear Models

ABSTRACTMixtures of Zellner’s g-priors have been studied extensively in linear models and have been shown to have numerous desirable properties for Bayesian variable selection and model averaging. ...
Domain growth and aging scaling in coarsening disordered systems

Using extensive Monte Carlo simulations we study aging properties of two disordered systems quenched below their critical point, namely the two-dimensional random-bond Ising model and the three-dimensional Edwards-Anderson Ising spin glass with a bimodal distribution of the coupling constants. We study the two-times autocorrelation and space-time correlation functions and show that in both systems a simple aging scenario prevails in terms of the scaling variable L(t)/L(s), where L is the time-dependent correlation length, whereas s is the waiting time and t is the observation time. The investigation of the space-time correlation function for the random-bond Ising model allows us to address some issues related to superuniversality.
Exploring 2-Group Global Symmetries

We analyze four-dimensional quantum field theories with continuous 2-group global symmetries. At the level of their charges, such symmetries are identical to a product of continuous flavor or spacetime symmetries with a 1-form global symmetry U(1) (1) , which arises from a conserved 2-form current J (2) . Rather, 2-group symmetries are characterized by deformed current algebras, with quantized structure constants, which allow two flavor currents or stress tensors to fuse into J (2) . This leads to unconventional Ward identities, which constrain the allowed patterns of spontaneous 2-group symmetry breaking and other aspects of the renormalization group flow. If J (2) is coupled to a 2-form background gauge field B(2), the 2-group current algebra modifies the behavior of B(2) under background gauge transformations. Its transformation rule takes the same form as in the Green-Schwarz mechanism, but only involves the background gauge or gravity fields that couple to the other 2-group currents. This makes it possible to partially cancel reducible ’t Hooft anomalies using Green-Schwarz counterterms for the 2-group background gauge fields. The parts that cannot be cancelled are reinterpreted as mixed, global anomalies involving U(1) (1) , which receive contributions from topological, as well as massless, degrees of freedom. Theories with 2-group symmetry are constructed by gauging an abelian flavor symmetry with suitable mixed ’t Hooft anomalies, which leads to many simple and explicit examples. Some of them have dynamical string excitations that carry U(1) (1) charge, and 2-group symmetry determines certain ’t Hooft anomalies on the world sheets of these strings. Finally, we point out that holographic theories with 2-group global symmetries have a bulk description in terms of dynamical gauge fields that participate in a conventional Green-Schwarz mechanism.
Initial Conditions for Inflation

Free scalar fields in de Sitter space have a one-parameter family of states invariant under the de Sitter group, including the standard thermal vacuum. We show that, except for the thermal vacuum, these states are unphysical when gravitational interactions are included. We apply these observations to the quantum state of the inflaton, and find that at best, dramatic fine tuning is required for states other than the thermal vacuum to lead to observable features in the CMBR anisotropy.
Temperature regulation in multicore processors using adjustable-gain integral controllers

This paper considers the problem of temperature regulation in multicore processors by dynamic voltage-frequency scaling. We propose a feedback law that is based on an integral controller with adjustable gain, designed for fast tracking convergence in the face of model uncertainties, time-varying plants, and tight computing-timing constraints. Moreover, unlike prior works we consider a nonlinear, time-varying plant model that trades off precision for simple and efficient on-line computations. Cycle-level, full system simulator implementation and evaluation illustrates fast and accurate tracking of given temperature reference values, and compares favorably with fixed-gain controllers.
A New, Bright, Short-Period, Emission Line Binary in Ophiuchus

The 11th magnitude star LS IV-08°3 has been classified previously as an OB star in the Luminous Stars survey, or alternatively as a hot subdwarf. It is actually a binary star. We present spectroscopy, spectroscopic orbital elements, and time-series photometry from observations made at the Kitt Peak National Observatory 2.1 m, Steward Observatory 2.3 m, MDM Observatory 1.3 m and 2.4 m, Hobby-Eberly 9.2 m, and Michigan State University 0.6 m telescopes. The star exhibits emission of varying strength in the cores of H and He I absorption lines. Emission is also present at 4686 A (He II) and near 4640/4650 A (N III/C III). Time-series spectroscopy collected from 2005 July to 2007 June shows coherent, periodic radial velocity variations of the Hα line, which we interpret as orbital motion with a period of 0.1952894(10) days. High-resolution spectra show that there are two emission components, one broad and one narrow, moving in antiphase, as might arise from an accretion disk and the irradiated face of the mass donor star. Less coherent, low-amplitude photometric variability is also present on a timescale similar to the orbital period. Diffuse interstellar bands indicate considerable reddening, which however is consistent with a distance of ~100-200 pc. The star is the likely counterpart of a weak ROSAT X-ray source, whose properties are consistent with accretion in a cataclysmic variable (CV) binary system. We classify LS IV-08°3 as a new member of the UX UMa subclass of CV stars.
Contact structures and reducible surgeries

We apply results from both contact topology and exceptional surgery theory to study when Legendrian surgery on a knot yields a reducible manifold. As an application, we show that a reducible surgery on a non-cabled positive knot of genus , leading to a proof of the cabling conjecture for positive knots of genus 2. Our techniques also produce bounds on the maximum Thurston–Bennequin numbers of cables.
Crystal structure solution from experimentally determined atomic pair distribution functions

An extension of the Liga algorithm for structure solution from atomic pair distribution functions (PDFs), to handle periodic crystal structures with multiple elements in the unit cell, is described. The procedure is performed in three separate steps. First, pair distances are extracted from the experimental PDF. In the second step the Liga algorithm is used to find unit-cell sites consistent with these pair distances. Finally, the atom species are assigned over the cell sites by minimizing the overlap of their empirical atomic radii. The procedure has been demonstrated on synchrotron X-ray PDF data from 16 test samples. The structure solution was successful for 14 samples, including cases with enlarged supercells. The algorithm success rate and the reasons for the failed cases are discussed, together with enhancements that should improve its convergence and usability.
Self-scattering for Dark Matter with an excited state

Self-interacting dark matter scenarios have recently attracted much attention, as a possible means to alleviate the tension between N-body simulations and observations of the dark matter distribution on galactic and sub-galactic scales. The presence of internal structure for the dark matter—for example, a nearly-degenerate state in the spectrum that could decay, or be collisionally excited or de-excited—has also been proposed as a possible means to address these discrepancies. Such internal structure can be a source of interesting signatures in direct and indirect dark matter searches, for example providing a novel explanation for the 3.5 keV line recently observed in galaxies and galaxy clusters. We analyze a simple model of dark matter self-scattering including a nearly-degenerate excited state, and develop an accurate analytic approximation for the elastic and inelastic s-wave cross sections, which is valid outside the perturbative regime provided the particle velocity is sufficiently low (this condition is also required for the s-wave to dominate over higher partial waves). We anticipate our results will be useful in incorporating inelastic self-scattering into N-body simulations, in order to study the quantitative impact of nearly-degenerate states in the dark matter spectrum on galactic structure and dynamics, and in computing the indirect signatures ofmore » multi-state dark matter.« less
Complete Embedded Self-Translating Surfaces Under Mean Curvature Flow

We describe a construction of complete embedded self-translating surfaces under mean curvature flow by desingularizing the intersection of a finite family of grim reapers in general position.
Expansion segments in bacterial and archaeal 5S ribosomal RNAs.

The large ribosomal RNAs of eukaryotes frequently contain expansion sequences that add to the size of the rRNAs but do not affect their overall structural layout and are compatible with major ribosomal function as an mRNA translation machine. The expansion of prokaryotic ribosomal RNAs is much less explored. In order to obtain more insight into the structural variability of these conserved molecules, we herein report the results of a comprehensive search for the expansion sequences in prokaryotic 5S rRNAs. Overall, 89 expanded 5S rRNAs of 15 structural types were identified in 15 archaeal and 36 bacterial genomes. Expansion segments ranging in length from 13 to 109 residues were found to be distributed among 17 insertion sites. The strains harboring the expanded 5S rRNAs belong to the bacterial orders Clostridiales, Halanaerobiales, Thermoanaerobacterales, and Alteromonadales as well as the archael order Halobacterales. When several copies of a 5S rRNA gene are present in a genome, the expanded versions may coexist with normal 5S rRNA genes. The insertion sequences are typically capable of forming extended helices, which do not seemingly interfere with folding of the conserved core. The expanded 5S rRNAs have largely been overlooked in 5S rRNA databases.