cssi/SciSciGPT-SciSciNet huggingface dataset:
Sub-Ramsey Numbers for Arithmetic Progressions

Let the integers 1, . . . ,n be assigned colors. Szemeredi's theorem implies that if there is a dense color class then there is an arithmetic progression of length three in that color. We study the conditions on the color classes forcing totally multicolored arithmetic progressions of length 3.Let f(n) be the smallest integer k such that there is a coloring of {1, . . . ,n} without totally multicolored arithmetic progressions of length three and such that each color appears on at most k integers. We provide an exact value for f(n) when n is sufficiently large, and all extremal colorings. In particular, we show that f(n)=8n/17+O(1). This completely answers a question of Alon, Caro and Tuza.
A master bosonization duality

We conjecture a new sequence of dualities between Chern-Simons gauge theories simultaneously coupled to fundamental bosons and fermions. These dualities reduce to those proposed by Aharony when the number of bosons or fermions is zero. Our conjecture passes a number of consistency checks. These include the matching of global symmetries and consistency with level/rank duality in massive phases.
Reflectionless excitation of arbitrary photonic structures: a general theory

We outline a recently developed theory of impedance-matching, or reflectionless excitation of arbitrary finite photonic structures in any dimension. It describes the necessary and sufficient conditions for perfectly reflectionless excitation to be possible, and specifies how many physical parameters must be tuned to achieve this. In the absence of geometric symmetries the tuning of at least one structural parameter will be necessary to achieve reflectionless excitation. The theory employs a recently identified set of complex-frequency solutions of the Maxwell equations as a starting point, which are defined by having zero reflection into a chosen set of input channels, and which are referred to as R-zeros. Tuning is generically necessary in order to move an R-zero to the real-frequency axis, where it becomes a physical steady-state solution, referred to as a Reflectionless Scattering Mode (RSM). Except in single-channel systems, the RSM corresponds to a particular input wavefront, and any other wavefront will generally not be reflectionless. In a structure with parity and time-reversal symmmetry or with parity-time symmetry, generically a subset of R-zeros is real, and reflectionless states exist without structural tuning. Such systems can exhibit symmetry-breaking transitions when two RSMs meet, which corresponds to a recently identified kind of exceptional point at which the shape of the reflection and transmission resonance lineshape is flattened.
Energy-throughput tradeoff in sustainable Cloud-RAN with energy harvesting

In this paper, we investigate joint beamforming for energy-throughput tradeoff in a sustainable cloud radio access network system, where multiple base stations (BSs) powered by independent renewable energy sources will collaboratively transmit wireless information and energy to the data receiver and the energy receiver simultaneously. In order to obtain the optimal joint beamforming design over a finite time horizon, we formulate an optimization problem to maximize the throughput of the data receiver while guaranteeing sufficient RF charged energy of the energy receiver. Although such problem is non-convex, it can be relaxed into a convex form and upper bounded by the optimal value of the relaxed problem. We further prove tightness of the upper bound by showing the optimal solution to the relaxed problem is rank one. Motivated by the optimal solution, an efficient online algorithm is also proposed for practical implementation. Finally, extensive simulations are performed to verify the superiority of the proposed joint beamforming strategy to other beamforming designs.
The bispectrum in the Effective Field Theory of Large Scale Structure

We study the bispectrum in the Effective Field Theory of Large Scale Structure, consistently accounting for the effects of short-scale dynamics. We begin by proving that, as long as the theory is perturbative, it can be formulated to arbitrary order using only operators that are local in time. We then derive all the new operators required to cancel the UV-divergences and obtain a physically meaningful prediction for the one-loop bispectrum. In addition to new, subleading stochastic noises and the viscosity term needed for the one-loop power spectrum, we find three new effective operators. The three new parameters can be constrained by comparing with N-body simulations. The best fit is precisely what is suggested by the structure of UV-divergences, hence justifying a formula for the EFTofLSS bispectrum whose only fitting parameter is already fixed by the power spectrum. This result predicts the bispectrum of N-body simulations up to kmax≈0.22 h Mpc−1 at 0z=, an improvement by nearly a factor of two as compared to one-loop standard perturbation theory.
Periodic Minimizers in 1D Local Mean Field Theory

There are not many physical systems where it is possible to demonstate rigorously that energy minimizers are periodic. Using reflection positivity techniques we prove, for a class of mesoscopic free-energies representing 1D systems with competing interactions, that all minimizers are either periodic, with zero average, or of constant sign. Examples of both phenomena are given. This extends our previous work where such results were proved for the ground states of lattice systems with ferromagnetic nearest neighbor interactions and dipolar type antiferromagnetic long range interactions.
Building a hydrodynamics code with kinetic theory

We report on the development of a test-particle based kinetic Monte Carlo code for large systems and its application to simulate matter in the continuum regime. Our code combines advantages of the Direct Simulation Monte Carlo and the Point-of-Closest-Approach methods to solve the collision integral of the Boltzmann equation. With that, we achieve a high spatial accuracy in simulations while maintaining computational feasibility when applying a large number of test-particles. The hybrid setup of our approach allows us to study systems which move in and out of the hydrodynamic regime, with low and high particle densities. To demonstrate our code's ability to reproduce hydrodynamic behavior we perform shock wave simulations and focus here on the Sedov blast wave test. The blast wave problem describes the evolution of a spherical expanding shock front and is an important verification problem for codes which are applied in astrophysical simulation, especially for approaches which aim to study core-collapse supernovae.
Improving vertebra segmentation through joint vertebra-rib atlases

Accurate spine segmentation allows for improved identification and quantitative characterization of abnormalities of the vertebra, such as vertebral fractures. However, in existing automated vertebra segmentation methods on computed tomography (CT) images, leakage into nearby bones such as ribs occurs due to the close proximity of these visibly intense structures in a 3D CT volume. To reduce this error, we propose the use of joint vertebra-rib atlases to improve the segmentation of vertebrae via multi-atlas joint label fusion. Segmentation was performed and evaluated on CTs containing 106 thoracic and lumbar vertebrae from 10 pathological and traumatic spine patients on an individual vertebra level basis. Vertebra atlases produced errors where the segmentation leaked into the ribs. The use of joint vertebra-rib atlases produced a statistically significant increase in the Dice coefficient from 92.5 ± 3.1% to 93.8 ± 2.1% for the left and right transverse processes and a decrease in the mean and max surface distance from 0.75 ± 0.60mm and 8.63 ± 4.44mm to 0.30 ± 0.27mm and 3.65 ± 2.87mm, respectively.
Spheres, charges, instantons, and bootstrap: A five-dimensional odyssey

We combine supersymmetric localization and the conformal bootstrap to study five-dimensional superconformal field theories. To begin, we classify the admissible counter-terms and derive a general relation between the five-sphere partition function and the conformal and flavor central charges. Along the way, we discover a new superconformal anomaly in five dimensions. We then propose a precise triple factorization formula for the five-sphere partition function, that incorporates instantons and is consistent with flavor symmetry enhancement. We numerically evaluate the central charges for the rank-one Seiberg and Morrison-Seiberg theories, and find strong evidence for their saturation of bootstrap bounds, thereby determining the spectra of long multiplets in these theories. Lastly, our results provide new evidence for the F-theorem and possibly a C-theorem in five-dimensional superconformal theories.
Volatile Delivery to Planets from Water-rich Planetesimals around Low Mass Stars

Most models of volatile delivery to accreting terrestrial planets assume that the carriers for water are similar in water content to the carbonaceous chondrites in our solar system. Here we consider how the water content of planetesimals may be higher in many planetary systems, as they could lack the short-lived radionuclides that drove water loss in carbonaceous chondrites in our solar system. Using N-body simulations, we explore how planetary accretion would be different if bodies beyond the water line contained a water-mass fraction consistent with chemical equilibrium calculations, and more similar to comets, as opposed to the more traditional water-depleted values. We apply this model to consider planet formation around stars of different masses and identify trends in the properties of habitable zone planets and planetary system architecture that could be tested by ongoing exoplanet census data collection. Comparison of such data with the model-predicted trends will serve to evaluate how well the N-body simulations and the initial conditions used in studies of planetary accretion can be used to understand this stage of planet formation.
Shaping coherent x-rays with binary optics

Diffractive lenses fabricated by lithographic methods are one of the most popular image forming optics in the x-ray regime. Most commonly, binary diffractive optics, such as Fresnel zone plates, are used due to their ability to focus at high resolution and to manipulate the x-ray wavefront. We report here a binary zone plate design strategy to form arbitrary illuminations for coherent multiplexing, structured illumination, and wavefront shaping experiments. Given a desired illumination, we adjust the duty cycle, harmonic order, and zone placement to vary both the amplitude and phase of the wavefront at the lens. This enables the binary lithographic pattern to generate arbitrary structured illumination optimized for a variety of applications such as holography, interferometry, ptychography, imaging, and others.
A STEREO Survey of Magnetic Cloud Coronal Mass Ejections Observed at Earth in 2008–2012

We identify coronal mass ejections (CMEs) associated with magnetic clouds (MCs) observed near Earth by the Wind spacecraft from 2008 to mid-2012, a time period when the two STEREO spacecraft were well positioned to study Earth-directed CMEs. We find 31 out of 48 Wind MCs during this period can be clearly connected with a CME that is trackable in STEREO imagery all the way from the Sun to near 1 AU. For these events, we perform full 3-D reconstructions of the CME structure and kinematics, assuming a flux rope morphology for the CME shape, considering the full complement of STEREO and SOHO imaging constraints. We find that the flux rope orientations and sizes inferred from imaging are not well correlated with MC orientations and sizes inferred from the Wind data. However, velocities within the MC region are reproduced reasonably well by the image-based reconstruction. Our kinematic measurements are used to provide simple prescriptions for predicting CME arrival times at Earth, provided for a range of distances from the Sun where CME velocity measurements might be made. Finally, we discuss the differences in the morphology and kinematics of CME flux ropes associated with different surface phenomena (flares, filament eruptions, or no surface activity).
Injectivity radii of hyperbolic integer homology 3-spheres

We construct hyperbolic integer homology 3–spheres where the injectivity radius is arbitrarily large for nearly all points of the manifold. As a consequence, there exists a sequence of closed hyperbolic 3–manifolds that Benjamini–Schramm converge to H whose normalized Ray–Singer analytic torsions do not converge to the L –analytic torsion of H . This contrasts with the work of Abert et al who showed that Benjamini– Schramm convergence forces convergence of normalized Betti numbers. Our results shed light on a conjecture of Bergeron and Venkatesh on the growth of torsion in the homology of arithmetic hyperbolic 3–manifolds, and we give experimental results which support this and related conjectures.
The Ricci Flow on Noncommutative Two-Tori

In this paper we construct a version of Ricci flow for noncommutative two-tori, based on a spectral formulation in terms of the eigenvalues and eigenfunction of the Laplacian and recent results on the Gauss–Bonnet theorem for noncommutative tori.
PROTON, ELECTRON, AND ION HEATING IN THE FAST SOLAR WIND FROM NONLINEAR COUPLING BETWEEN ALFVÉNIC AND FAST-MODE TURBULENCE

In the parts of the solar corona and solar wind that experience the fewest Coulomb collisions, the component proton, electron, and heavy ion populations are not in thermal equilibrium with one another. Observed differences in temperatures, outflow speeds, and velocity distribution anisotropies are useful constraints on proposed explanations for how the plasma is heated and accelerated. This paper presents new predictions of the rates of collisionless heating for each particle species, in which the energy input is assumed to come from magnetohydrodynamic (MHD) turbulence. We first created an empirical description of the radial evolution of Alfven, fast-mode, and slow-mode MHD waves. This model provides the total wave power in each mode as a function of distance along an expanding flux tube in the high-speed solar wind. Next, we solved a set of cascade advection-diffusion equations that give the time-steady wavenumber spectra at each distance. An approximate term for nonlinear coupling between the Alfven and fast-mode fluctuations is included. For reasonable choices of the parameters, our model contains enough energy transfer from the fast mode to the Alfven mode to excite the high-frequency ion cyclotron resonance. This resonance is efficient at heating protons and other ions in the direction perpendicular to the background magnetic field, and our model predicts heating rates for these species that agree well with both spectroscopic and in situ measurements. Nonetheless, the high-frequency waves comprise only a small part of the total Alfvenic fluctuation spectrum, which remains highly two dimensional as is observed in interplanetary space.
Variational approach to unsupervised learning

Deep belief networks are used extensively for unsupervised stochastic learning on large datasets. Compared to other deep learning approaches their layer-by-layer learning makes them highly scalable. Unfortunately, the principles by which they achieve efficient learning are not well understood. Numerous attempts have been made to explain their efficiency and applicability to a wide class of learning problems in terms of principles drawn from cognitive psychology, statistics, information theory, and more recently physics, but quite often these imported principles lack strong scientific foundation. Here we demonstrate how one can arrive at convolutional deep belief networks as potential solution to unsupervised learning problems without making assumptions about the underlying framework. To do this, we exploit the notion of symmetry that is fundamental in machine learning, physics and other fields, utilizing the particular form of the functional renormalization group in physics.
Asymptotic distribution for the birthday problem with multiple coincidences, via an embedding of the collision process†

We study the random variable B(c, n), which counts the number of balls that must be thrown into n equally-sized bins in order to obtain c collisions. The asymptotic expected value of B(1, n) is the well-known appearing in the solution to the birthday problem; the limit distribution and asymptotic moments of B(1, n) are also well known. We calculate the distribution and moments of B(c, n) asymptotically as n goes to ∞ and c = O(n). We have two main tools: an embedding of the collision process — realizing the process as a deterministic function of the standard Poisson process — and a central limit result by Renyi. © 2015 Wiley Periodicals, Inc. Random Struct. Alg., 2015
Ideal multipole ion traps from planar ring electrodes

We present designs for multipole ion traps based on a set of planar, annular, concentric electrodes which require only rf potentials to confine ions. We illustrate the desirable properties of the traps by considering a few simple cases of confined ions. We predict that mm-scale surface traps may have trap depths as high as tens of electron volts when parameters of a magnitude common in the field are chosen. Under similar conditions, micromotion amplitudes in a 2D ion crystal as low as tens of nanometers could be realized. Several example traps are studied, and the scaling of those properties with voltage, frequency, and trap scale, for small numbers of ions, is derived. Applications of these traps include quantum information science, frequency metrology, and cold ion–atom collisions.
On the Compared Accuracy and Reliability of Spectroscopic and Photometric Redshift Measurements

We present a comparison between the catalog of spectroscopic redshifts in the Hubble Deep Field (HDF) recently published by Cohen and collaborators and the redshifts that our group has measured for the same objects using photometric techniques. This comparison is performed in order to fully characterize the errors associated with the photometric redshift technique. The compilation of spectroscopic redshifts incorporates previously published results, corrections to previously published wrong values, and new data, and it includes over 140 objects in the HDF proper. It represents the deepest, cleanest, most complete spectroscopic catalog ever compiled. We particularly study each and every object for which our redshift and the one measured by Cohen and collaborators seem to disagree. In most of those cases, the photometric evidence we put forth is strong enough to call for a careful review of the spectroscopic values, since the spectroscopic values seem to be in error. We show that it is possible to characterize the systematic errors associated with our technique, which when combined with the well-measured photometric errors allow us to obtain complete information on the redshift of each galaxy and its associated confidence interval, regardless of its apparent magnitude. One of the main conclusions of this study is that, to date, all the redshifts from our published catalog that have been checked have been shown to be correct (within the stated confidence limits). This implies that our set of spectrophotometric galaxy templates is a fair representation of the galaxy population at all redshifts (0 < z < 6) and magnitudes (R < 24) explored thus far. On the other hand, spectroscopy of faint sources is subject to unknown and uncharacterized systematic errors. These errors will in turn be transmitted to any photometric redshift technique that uses spectroscopic samples in its calibration. Our analysis proves that photometric redshift techniques can and must be used to extend the range of applicability (in redshift, signal-to-noise, and apparent magnitude) of the spectroscopic redshift measurements.
Four-fermion interaction from torsion as dark energy

The observed small, positive cosmological constant may originate from a four-fermion interaction generated by the spin-torsion coupling in the Einstein–Cartan–Sciama–Kibble gravity if the fermions are condensing. In particular, such a condensation occurs for quark fields during the quark-gluon/hadron phase transition in the early Universe. We study how the torsion-induced four-fermion interaction is affected by adding two terms to the Dirac Lagrangian density: the parity-violating pseudoscalar density dual to the curvature tensor and a spinor-bilinear scalar density which measures the nonminimal coupling of fermions to torsion.
Container solutions for HPC Systems: A Case Study of Using Shifter on Blue Waters

Software container solutions have revolutionized application development approaches by enabling lightweight platform abstractions within the so-called "containers." Several solutions are being actively developed in attempts to bring the benefits of containers to high-performance computing systems with their stringent security demands on the one hand and fundamental resource sharing requirements on the other.In this paper, we discuss the benefits and short-comings of such solutions when deployed on real HPC systems and applied to production scientific applications. We highlight use cases that are either enabled by or significantly benefit from such solutions. We discuss the efforts by HPC system administrators and support staff to support users of these type of workloads on HPC systems not initially designed with these workloads in mind focusing on NCSA's Blue Waters system.
COOLING AND HEATING FUNCTIONS OF PHOTOIONIZED GAS

Cooling functions of cosmic gas are a crucial ingredient for any study of gas dynamics and thermodynamics in the interstellar and intergalactic medium. As such, they have been studied extensively in the past under the assumption of collisional ionization equilibrium. However, for a wide range of applications, the local radiation field introduces a non-negligible, often dominant, modification to the cooling and heating functions. In the most general case, these modifications cannot be described in simple terms, and would require a detailed calculation with a large set of chemical species using a radiative transfer code (the well-known code Cloudy, for example). We show, however, that for a sufficiently general variation in the spectral shape and intensity of the incident radiation field, the cooling and heating functions can be approximated as depending only on (1) the photodissociation rate of molecular hydrogen, (2) the hydrogen photo-ionization rate, and (3) the photo-ionization rate of OVIII;more complex and more accurate approximations also exist. Such dependence is easy to tabulate and implement in cosmological or galactic-scale simulations, thus economically accounting for an important but rarely-included factor in the evolution of cosmic gas. We also show a few examples where the radiation environment has a large effect,more » the most spectacular of which is a quasar that suppresses gas cooling in its host halo without any mechanical or non-radiative thermal feedback.« less
Characterization of the Reflectivity of Various Black Materials

We present total and specular reflectance measurements of various materials that are commonly (and uncommonly) used to provide baffling and/or to minimize the effect of stray light in optical systems. More specifically, we investigate the advantage of using certain black surfaces and their role in suppressing stray light on detectors in optical systems. We measure the total reflectance of the samples over a broad wavelength range (250 < λ < 2500 nm) that is of interest to astronomical instruments in the ultraviolet, visible, and near-infrared regimes. Additionally, we use a helium-neon laser to measure the specular reflectance of the samples at various angles. Finally, we compare these two measurements and derive the specular fraction for each sample.
Visual Chirality

How can we tell whether an image has been mirrored? While we understand the geometry of mirror reflections very well, less has been said about how it affects distributions of imagery at scale, despite widespread use for data augmentation in computer vision. In this paper, we investigate how the statistics of visual data are changed by reflection. We refer to these changes as ``visual chirality,'' after the concept of geometric chirality---the notion of objects that are distinct from their mirror image. Our analysis of visual chirality reveals surprising results, including low-level chiral signals pervading imagery stemming from image processing in cameras, to the ability to discover visual chirality in images of people and faces. Our work has implications for data augmentation, self-supervised learning, and image forensics.
Possible Production of Solar Spicules by Microfilament Eruptions

We examine Big Bear Solar Observatory (BBSO) Goode Solar Telescope (GST) high spatial resolution (006), high-cadence (3.45 s), Hα-0.8 A images of central-disk solar spicules, using data of Samanta et al. We compare with coronal-jet chromospheric-component observations of Sterling et al. Morphologically, bursts of spicules, referred to as "enhanced spicular activities" by Samanta et al., appear as scaled-down versions of the jet's chromospheric component. Both the jet and the enhanced spicular activities appear as chromospheric-material strands, undergoing twisting-type motions of ~20–50 km s−1 in the jet and ~20–30 km s−1 in the enhanced spicular activities. Presumably, the jet resulted from a minifilament-carrying magnetic eruption. For two enhanced spicular activities that we examine in detail, we find tentative candidates for corresponding erupting microfilaments, but not the expected corresponding base brightenings. Nonetheless, the enhanced-spicular-activities' interacting mixed-polarity base fields, frequent-apparent-twisting motions, and morphological similarities to the coronal jet's chromospheric-temperature component, suggest that erupting microfilaments might drive the enhanced spicular activities but be hard to detect, perhaps due to Hα opacity. Degrading the BBSO/GST-image resolution with a 10-FWHM smoothing function yields enhanced spicular activities resembling the "classical spicules" described by, e.g., Beckers. Thus, a microfilament eruption might be the fundamental driver of many spicules, just as a minifilament eruption is the fundamental driver of many coronal jets. Similarly, a 05-FWHM smoothing renders some enhanced spicular activities to resemble previously reported "twinned" spicules, while the full-resolution features might account for spicules sometimes appearing as 2D-sheet-like structures.
Non simply-laced symmetry algebras in F-theory on singular spaces

We demonstrate how non-simply-laced gauge and flavor symmetries arise in F-theory on spaces with non-isolated singularities. The breaking from a simply-laced symmetry to one that is non-simply-laced is induced by Calabi-Yau complex structure deformation. In all examples the deformation maintains non-isolated singularities but is accompanied by a splitting of an I1 seven-brane that opens new loops in the geometry near a non-abelian seven-brane. The splitting also arises in the moduli space of a probe D3-brane, which upon traversing the new loop experiences a monodromy that acts on 3-7 string junctions on the singular space. The monodromy reduces the symmetry algebra, which is the flavor symmetry of the D3-brane and the gauge symmetry of the seven-brane, to one that is non-simply-laced. A collision of the D3-brane with the seven-brane gives rise to a 4d $$ \mathcal{N}=1 $$ SCFT with a non-simply-laced flavor symmetry.
Estimating CDM particle trajectories in the mildly non-linear regime of structure formation. Implications for the density field in real and redshift space

We obtain approximations for the CDM particle trajectories starting from Lagrangian Perturbation Theory. These estimates for the CDM trajectories result in approximations for the density in real and redshift space, as well as for the momentum density that are better than what standard Eulerian and Lagrangian perturbation theory give. For the real space density, we find that our proposed approximation gives a good cross-correlation ( > 95%) with the non-linear density down to scales almost twice smaller than the non-linear scale, and six times smaller than the corresponding scale obtained using linear theory. This allows for a speed-up of an order of magnitude or more in the scanning of the cosmological parameter space with N-body simulations for the scales relevant for the baryon acoustic oscillations. Possible future applications of our method include baryon acoustic peak reconstruction, building mock galaxy catalogs, momentum field reconstruction.
Cosmic Reionization on Computers. I. Design and Calibration of Simulations

Cosmic Reionization On Computers is a long-term program of numerical simulations of cosmic reionization. Its goal is to model fully self-consistently (albeit not necessarily from the first principles) all relevant physics, from radiative transfer to gas dynamics and star formation, in simulation volumes of up to 100 comoving Mpc, and with spatial resolution approaching 100 pc in physical units. In this method paper, we describe our numerical method, the design of simulations, and the calibration of numerical parameters. Using several sets (ensembles) of simulations in 20 h –1 Mpc and 40 h –1 Mpc boxes with spatial resolution reaching 125 pc at z = 6, we are able to match the observed galaxy UV luminosity functions at all redshifts between 6 and 10, as well as obtain reasonable agreement with the observational measurements of the Gunn-Peterson optical depth at z < 6.
A CORRELATION BETWEEN CIRCUMSTELLAR DISKS AND ROTATION IN THE UPPER SCORPIUS OB ASSOCIATION

We present projected rotational velocities for 20 early-type (B8-A9) and 74 late-type (F2-M8) members of the {approx}5 Myr old Upper Scorpius OB Association derived from high-dispersion optical spectra obtained with the High Resolution Echelle Spectrometer on Keck I and the Magellan Inamori Kyocera Echelle on the Magellan Clay telescope. The spectroscopic sample is composed of stars and brown dwarfs with infrared signatures of circumstellar disks, both primordial and debris, and non-excess sources of comparable spectral type. We merge projected rotational velocities, accretion diagnostics, and Spitzer Space Telescope Infrared Array Camera and Multiband Imaging Photometer for Spitzer 24 {mu}m photometry to examine the relationship between rotation and circumstellar disks. The rotational velocities are strongly correlated with spectral type, a proxy for mass, such that the median vsin i for B8-A9-type stars is: 195 {+-} 70 km s{sup -1}, F2-K4: 37.8 {+-} 7.4 km s{sup -1}, K5-K9: 13.8{sup +21.3}{sub -8.2} km s{sup -1}, M0-M5: 16.52 {+-} 5.3 km s{sup -1}, and M5.5-M8: 17.72 {+-} 8.1 km s{sup -1}. We find with a probability of {>=}0.99 that M-type stars and brown dwarfs having infrared excess suggestive of circumstellar disks rotate more slowly than their non-excess counterparts. A similar correlation is present among F2-K9-typemore » stars, but only at the {approx}97% confidence level. Among the early-type (B8-A9) members, rotational velocities of the debris-disk and non-disk populations are indistinguishable. Considering the late-type (F2-M8) stars and brown dwarfs, we find a low fraction of slowly rotating, non-excess sources relative to younger star-forming regions, suggesting that most have spun up following disk dissipation. The few late-type (F2-M5) debris disk sources, which may be representative of stars that have recently dispersed their inner disks, are evenly divided between slow and moderate rotators.« less
Stationary configurations imply shift symmetry: no Bondi accretion for quintessence/k-essence

In this paper we show that, for general scalar fields, stationary configurations are possible for shift symmetric theories only. This symmetry with respect to constant translations in field space should either be manifest in the original field variables or reveal itself after an appropriate field redefinition. In particular this result implies that neither k- Essence nor Quintessence can have exact steady state / Bondi accretion onto Black Holes. We also discuss the role of field redefinitions in k-Essence theories. Here we study the transformation properties of observables and other variables in k-Essence and emphasize which of them are covariant under field redefinitions. Finally we find that stationary field configurations are necessarily linear in Killing time, provided that shift symmetry is realized in terms of these field variables.
Taylor expansions of groups and filtered-formality

Let G be a finitely generated group, and let $$\Bbbk {G}$$ be its group algebra over a field of characteristic 0. A Taylor expansion is a certain type of map from G to the degree completion of the associated graded algebra of $$\Bbbk {G}$$ which generalizes the Magnus expansion of a free group. The group G is said to be filtered-formal if its Malcev Lie algebra is isomorphic to the degree completion of its associated graded Lie algebra. We show that G is filtered-formal if and only if it admits a Taylor expansion, and derive some consequences.
Optimal polynomial based quantum eigenstate filtering with application to solving quantum linear systems

Author(s): Lin, L; Tong, Y | Abstract: We present a quantum eigenstate filtering algorithm based on quantum signal processing (QSP) and minimax polynomials. The algorithm allows us to efficiently prepare a target eigenstate of a given Hamiltonian, if we have access to an initial state with non-trivial overlap with the target eigenstate and have a reasonable lower bound for the spectral gap. We apply this algorithm to the quantum linear system problem (QLSP), and present two algorithms based on quantum adiabatic computing (AQC) and quantum Zeno effect respectively. Both algorithms prepare the final solution as a pure state, and achieves the near optimal Oe(dκlog(1/∊)) query complexity for a d-sparse matrix, where κ is the condition number, and ∊ is the desired precision. Neither algorithm uses phase estimation or amplitude amplification.
Making, probing and understanding ultracold Fermi gases

This paper summarizes the experimental frontier of ultracold fermionic gases. It is based on three lectures which one of the authors gave at the Varenna Summer School describing the experimental techniques used to study ultracold fermionic gases, and some of the results obtained so far. In many ways, the area of ultracold fermionic gases has grown out of the study of Bose-Einstein condensates. After their first experimental realizations in 1995 [1,2], the field of BEC has grown explosively. Most of the explored physics was governed by mean-field interactions, conveniently described by the Gross-Pitaevskii equation. One novel feature of trapped inhomogeneous gases was the spatially varying density, that allowed for the direct observation of the condensate, but also led to new concepts of surface effects and collective excitations which depended on the shape of the cloud. The experimental and theoretical explorations of these and other features have been a frontier area for a whole decade!
Orthogonal structure and orthogonal series in and on a double cone or a hyperboloid

We consider orthogonal polynomials on the surface of a double cone or a hyperboloid of revolution, either finite or infinite in axis direction, and on the solid domain bounded by such a surface and, when the surface is finite, by hyperplanes at the two ends. On each domain a family of orthogonal polynomials, related to the Gegebauer polynomials, is study and shown to share two characteristic properties of spherical harmonics: they are eigenfunctions of a second order linear differential operator with eigenvalues depending only on the polynomial degree, and they satisfy an addition formula that provides a closed form formula for the reproducing kernel of the orthogonal projection operator. The addition formula leads to a convolution structure, which provides a powerful tool for studying the Fourier orthogonal series on these domains. Furthermore, another family of orthogonal polynomials, related to the Hermite polynomials, is defined and shown to be the limit of the first family, and their properties are derived accordingly.
Chiral symmetry breaking in (2+1) dimensional QED

Abstract We study dynamical mass generation in QED in (2+1) dimensions using Hamiltonian lattice methods. We use staggered fermions, and perform simulations with explicit dynamical fermions in the chiral limit. We demonstrate that a recently developed method to reduce the fermion sign problem can successfully be applied to this problem. Our results are in agreement with both the strong coupling expansion and with Euclidean lattice simulations.
Nonlinear mushy-layer convection with chimneys: stability and optimal solute fluxes

We model buoyancy-driven convection with chimneys ‐ channels of zero solid fraction ‐ in a mushy layer formed during directional solidification of a binary alloy in two dimensions. A large suite of numerical simulations is combined with scaling analysis in order to study the parametric dependence of the flow. Stability boundaries are calculated for states of finite-amplitude convection with chimneys, which for a narrow domain can be interpreted in terms of a modified Rayleigh number criterion based on the domain width and mushy-layer permeability. For solidification in a wide domain with multiple chimneys, it has previously been hypothesized that the chimney spacing will adjust to optimize the rate of removal of potential energy from the system. For a wide variety of initial liquid concentration conditions, we consider the detailed flow structure in this optimal state and derive scaling laws for how the flow evolves as the strength of convection increases. For moderate mushy-layer Rayleigh numbers these flow properties support a solute flux that increases linearly with Rayleigh number. This behaviour does not persist indefinitely, however, with porosity-dependent flow saturation resulting in sublinear growth of the solute flux for sufficiently large Rayleigh numbers. Finally, we consider the influence of the porosity dependence of permeability, with a cubic function and a Carman‐Kozeny permeability yielding qualitatively similar system dynamics and flow profiles for the optimal states.
Developments of Highly Multiplexed, Multi-chroic Pixels for Balloon-Borne Platforms

We present our work to develop and characterize low thermal conductance bolometers that are part of sinuous antenna multi-chroic pixels (SAMP). We use longer, thinner and meandered bolometer legs to achieve 9 pW/K thermal conductance bolometers. We also discuss the development of inductor–capacitor chips operated at 4 K to extend the multiplexing factor of the frequency domain multiplexing to 105, an increase of 60% compared to the factor currently demonstrated for this readout system. This technology development is motivated by EBEX-IDS, a balloon-borne polarimeter designed to characterize the polarization of foregrounds and to detect the primordial gravity waves through their B-mode signature on the polarization of the cosmic microwave background. EBEX-IDS will operate 20,562 transition edge sensor bolometers spread over 7 frequency bands between 150 and 360 GHz. Balloon and satellite platforms enable observations at frequencies inaccessible from the ground and with higher instantaneous sensitivity. This development improves the readiness of the SAMP and frequency domain readout technologies for future satellite applications.
Intermediate-mass black holes in galactic nuclei

We present the first homogeneous sample of ntermediate-mass black hole candidates in active galactic nuclei. Starting with broad-line active nuclei from the Sloan Digital Sky Survey, we use the linewidth-luminosity-mass scaling relation to select a sample of 19 galaxies in the mass range M_(BH) ≈ 8 × 10^4 – 10^6M_⊙. In contrast to the local active galaxy population, the host galaxies are ~ 1 mag fainter than M∗ and thus are probably late-type systems. The active nuclei are also faint, with M_g ≈ −15 to −18 mag, while the bolometric luminosities are close to the Eddington limit. The spectral properties of the sample are compared to the related class of objects known as narrow-line Seyfert 1 galaxies. We discuss the importance of our sample as observational analogues of primordial black holes, contributors to the integrated signal for future gravitational wave experiments, and as a valuable tool in the calibration of the M_(BH)−σ_* relation.
Masers and star formation

Recent observational and theoretical advances concerning astronomical masers in star forming regions are reviewed. Major masing species are considered individually and in combination. Key results are summarized with emphasis on present science and future prospects.
Best-Bet Astrophysical Neutrino Sources

Likely astrophysical sources of detectable high-energy (>>TeV) neutrinos are considered. Based on gamma-ray emission properties, the most probable sources of neutrinos are argued to be GRBs, blazars, microquasars, and supernova remnants. Di use neutrino sources are also briefly considered.
SLIP: Learning to predict in unknown dynamical systems with long-term memory

We present an efficient and practical (polynomial time) algorithm for online prediction in unknown and partially observed linear dynamical systems (LDS) under stochastic noise. When the system parameters are known, the optimal linear predictor is the Kalman filter. However, the performance of existing predictive models is poor in important classes of LDS that are only marginally stable and exhibit long-term forecast memory. We tackle this problem through bounding the generalized Kolmogorov width of the Kalman filter model by spectral methods and conducting tight convex relaxation. We provide a finite-sample analysis, showing that our algorithm competes with Kalman filter in hindsight with only logarithmic regret. Our regret analysis relies on Mendelson's small-ball method, providing sharp error bounds without concentration, boundedness, or exponential forgetting assumptions. We also give experimental results demonstrating that our algorithm outperforms state-of-the-art methods. Our theoretical and experimental results shed light on the conditions required for efficient probably approximately correct (PAC) learning of the Kalman filter from partially observed data.
Reduction of surface spin-induced electron spin relaxations in nanodiamonds

Nanodiamonds (NDs) hosting nitrogen-vacancy (NV) centers are promising for applications of quantum sensing. Long spin relaxation times ( T 1 and T 2) are critical for high sensitivity in quantum applications. It has been shown that fluctuations of magnetic fields due to surface spins strongly influence T 1 and T 2 in NDs. However, their relaxation mechanisms have yet to be fully understood. In this paper, we investigate the relation between surface spins and T 1 and T 2 of single-substitutional nitrogen impurity (P1) centers in NDs. The P1 centers located typically in the vicinity of NV centers are a great model system to study the spin relaxation processes of the NV centers. By employing high-frequency electron paramagnetic resonance spectroscopy, we verify that air annealing removes surface spins efficiently and significantly reduces their contribution to T 1.
How to Make the Earth Orbit the Sun in 1614

In 1614 the Jesuit astronomer Christoph Scheiner and his student, Johann Georg Locher, proposed a physical mechanism to explain how the Earth could orbit the sun. An orbit, they said, is a perpetua...
ON THE CONSERVATION OF CROSS HELICITY AND WAVE ACTION IN SOLAR-WIND MODELS WITH NON-WKB ALFVEN WAVE REFLECTION

The interaction between Alfven-wave turbulence and the background solar wind affects the cross helicity () in two ways. Non-WKB reflection converts outward-propagating Alfven waves into inward-propagating Alfven waves and vice versa, and the turbulence transfers momentum to the background flow. When both effects are accounted for, the total cross helicity is conserved. In the special case that the background density and flow speed are independent of time, the equations of cross-helicity conservation and total-energy conservation can be combined to recover a well-known equation derived by Heinemann and Olbert that has been interpreted as a non-WKB generalization of wave-action conservation. This latter equation (in contrast to cross-helicity and energy conservation) does not hold when the background varies in time.
Spin-Down Measurement of PSR J1852+0040 in Kesteven 79: Central Compact Objects as Anti-Magnetars

Using XMM-Newton and Chandra, we achieved phase-connected timing of the 105 ms X-ray pulsar PSR J1852+0040 that provides the first measurement of the spin-down rate of a member of the class of central compact objects (CCOs) in supernova remnants. We measure P-dot=(8.68+-0.09) x 10{sup -18}, and find no evidence for timing noise or variations in X-ray flux over 4.8 year. In the dipole spin-down formalism, this implies a surface magnetic field strength B{sub s} = 3.1 x 10{sup 10} G, the smallest ever measured for a young neutron star, and consistent with being a fossil field. In combination with upper limits on B{sub s} from other CCO pulsars, this is strong evidence in favor of the 'anti-magnetar' explanation for their low luminosity and lack of magnetospheric activity or synchrotron nebulae. While this dipole field is small, it can prevent accretion of sufficient fall-back material so that the observed X-ray luminosity of L{sub x} = 5.3 x 10{sup 33}(d/7.1 kpc){sup 2} erg s{sup -1} must instead be residual cooling. The spin-down luminosity of PSR J1852+0040, E-dot=3.0 x 10{sup 32} erg s{sup -1}, is an order of magnitude smaller than L{sub x} . Fitting of the X-ray spectrum to two blackbodies findsmore » small emitting radii, R{sub 1} = 1.9 km and R{sub 2} = 0.45 km, for components of kT{sub 1} = 0.30 keV and kT{sub 2} = 0.52 keV, respectively. Such small, hot regions are ubiquitous among CCOs, and are not yet understood in the context of the anti-magnetar picture because anisotropic surface temperature is usually attributed to the effects of strong magnetic fields.« less
Dynamic Stability of Equilibrium Capillary Drops

We investigate a model for contact angle motion of quasi-static capillary drops resting on a horizontal plane. We prove global in time existence and long time behavior (convergence to equilibrium) in a class of star-shaped initial data for which we show that topological changes of drops can be ruled out for all times. Our result applies to any drop which is initially star-shaped with respect to a small ball inside the drop, given that the volume of the drop is sufficiently large. For the analysis, we combine geometric arguments based on the moving-plane type method with energy dissipation methods based on the formal gradient flow structure of the problem.
ULTRA-HIGH-RESOLUTION INTENSITY STATISTICS OF A SCINTILLATING SOURCE

We derive the distribution of flux density of a compact source exhibiting strong diffractive scintillation. Our treatment accounts for arbitrary spectral averaging, spatially extended source emission, and the possibility of intrinsic variability within the averaging time, as is typical for pulsars. We also derive the modulation index and present a technique for estimating the self-noise of the distribution, which can be used to identify amplitude variations on timescales shorter than the spectral accumulation time. Our results enable a direct comparison with ultra-high-resolution observations of pulsars, particularly single-pulse studies with Nyquist-limited resolution, and can be used to identify the spatial emission structure of individual pulses at a small fraction of the diffractive scale.