cssi/SciSciGPT-SciSciNet huggingface dataset:
Deep Sinogram Completion With Image Prior for Metal Artifact Reduction in CT Images

Computed tomography (CT) has been widely used for medical diagnosis, assessment, and therapy planning and guidance. In reality, CT images may be affected adversely in the presence of metallic objects, which could lead to severe metal artifacts and influence clinical diagnosis or dose calculation in radiation therapy. In this article, we propose a generalizable framework for metal artifact reduction (MAR) by simultaneously leveraging the advantages of image domain and sinogram domain-based MAR techniques. We formulate our framework as a sinogram completion problem and train a neural network (SinoNet) to restore the metal-affected projections. To improve the continuity of the completed projections at the boundary of metal trace and thus alleviate new artifacts in the reconstructed CT images, we train another neural network (PriorNet) to generate a good prior image to guide sinogram learning, and further design a novel residual sinogram learning strategy to effectively utilize the prior image information for better sinogram completion. The two networks are jointly trained in an end-to-end fashion with a differentiable forward projection (FP) operation so that the prior image generation and deep sinogram completion procedures can benefit from each other. Finally, the artifact-reduced CT images are reconstructed using the filtered backward projection (FBP) from the completed sinogram. Extensive experiments on simulated and real artifacts data demonstrate that our method produces superior artifact-reduced results while preserving the anatomical structures and outperforms other MAR methods.
The intrinsic neonatal hippocampal network: rsfMRI findings

Many adults cannot voluntarily recall memories before the ages of 3-5, a phenomenon referred to as "infantile amnesia." The development of the hippocampal network likely plays a significant part in the emergence of the ability to form long-lasting memories. In adults, the hippocampus has specialized and privileged connections with certain cortical networks, which presumably facilitate its involvement in memory encoding, consolidation, and retrieval. Is the hippocampus already specialized in these cortical connections at birth? And are the topographical principles of connectivity (e.g., long-axis specialization) present at birth? We analyzed resting-state hippocampal connectivity in neonates scanned within 1 wk of birth (Developmental Human Connectome Project) and compared it with that of adults (Human Connectome Project). We explored the connections of the whole hippocampus and its long-axis specialization to seven canonical cortical networks. We found that the neonatal hippocampal networks show clear immaturity at birth: adults showed hippocampal connectivity that was unique for each cortical network, whereas neonates showed no differentiation in hippocampal connectivity across these networks. Furthermore, neonates lacked long-axis specialization (i.e., along the anterior-posterior axis) of the hippocampus in its differential connectivity patterns to the cortical networks. This immaturity in connectivity may contribute to immaturity in memory formation in the first years of life.NEW & NOTEWORTHY Although both animal data and human data suggest that the hippocampus is immature at birth, to date, there are no direct assessments of human hippocampal functional connectivity (FC) very early in life. Our study explores the FC of the hippocampus to the cortex at birth, allowing insight into the development of human memory systems. In particular, we find that adults and neonates exhibit vastly different hippocampal connectivity profiles-a finding that likely has large developmental implications.
Evaluating the Potential of Drone Swarms in Nonverbal HRI Communication

Human-to-human communications are enriched with affects and emotions, conveyed, and perceived through both verbal and nonverbal communication. It is our thesis that drone swarms can be used to communicate information enriched with effects via nonverbal channels: guiding, generally interacting with, or warning a human audience via their pattern of motions or behavior. And furthermore that this approach has unique advantages such as flexibility and mobility over other forms of user interface.In this paper, we present a user study to understand how human participants perceived and interpreted swarm behaviors of micro-drone Crazyflie quadcopters flying three different flight formations to bridge the psychological gap between front-end technologies (drones) and the human observers’ emotional perceptions. We ask the question whether a human observer would in fact consider a swarm of drones in their immediate vicinity to be nonthreatening enough to be a vehicle for communication, and whether a human would intuit some communication from the swarm behavior, despite the lack of verbal or written language.Our results show that there is statistically significant support for the thesis that a human participant is open to interpreting the motion of drones as having intent and to potentially interpret their motion as communication. This supports the potential use of drone swarms as a communication resource, emergency guidance situations, policing of public events, tour guidance, etc.
Dynamic Pricing of Relocating Resources in Large Networks

Motivated by applications in shared vehicle systems, we study dynamic pricing of resources that relocate over a network of locations. Customers with private willingness to pay sequentially request ...
The source of lattice rotation in rotating lattice single (RLS) crystals

Abstract Laser heating can be used to produce single crystal architectures in glass with a lattice that rotates at a constant rate. Such metamaterials can offer properties that are disallowed by conventional crystal structures. To establish the mechanism of this lattice rotation, we used transmission electron microscopy (TEM) to directly observe and characterize dislocations in Sb2S3 crystal lines fabricated in Sb-S-I glass as a model system. The lattice rotation calculated from the density and Burgers vectors of edge dislocations agrees with lattice rotation values experimentally determined by electron backscatter diffraction (EBSD) and selected area diffraction patterns (SADP). These results provide the first direct proof of the dislocation mechanism of lattice rotation in rotating lattice single (RLS) crystals, and very likely other forms of growth actuated bending, twisting and noncrystallographic branching as seen in spherulites.
Finding duality for Riesz bases of exponentials on multi-tiles

Abstract It is known [6] , [14] , [19] that if Ω ⊂ R d belongs to a class of k-tiling domains when translated by a lattice Λ, there exists a Riesz basis of exponentials for L 2 ( Ω ) constructed using k translates of the dual lattice Λ ⁎ . In this paper, we give an explicit construction of the corresponding biorthogonal dual Riesz basis. We also extend the iterative reconstruction algorithm introduced in [11] to this setting.
Anisotropic Stars II: Stability

We investigate the stability of self-gravitating spherically symmetric anisotropic spheres under radial perturbations. We consider both the Newtonian and the full general-relativistic perturbation treatment. In the general-relativistic case, we extend the variational formalism for spheres with isotropic pressure developed by Chandrasekhar. We find that, in general, when the tangential pressure is greater than the radial pressure, the stability of the anisotropic sphere is enhanced when compared to isotropic configurations. In particular, anisotropic spheres are found to be stable for smaller values of the adiabatic index γ.
Solving the radial Dirac equations: a numerical odyssey

We discuss, in a pedagogical way, how to solve for relativistic wavefunctions from the radial Dirac equations. We first solve the equations for a linear Lorentz scalar potential, Vs(r), that provides for confinement of a quark; the case of massless u and d quarks is necessarily relativistic. We use an iterative 'shooting and matching' procedure to find the eigenenergies and the upper and lower component wavefunctions. Solutions for the massive quarks (s, c, and b) are also presented. We then consider the Coulomb potential [Vv(r), 0]. We re-derive, numerically, the (analytically well-known) relativistic hydrogen atom eigenenergies and wavefunctions, and later extend that to the cases of heavier one-electron atoms and muonic atoms. Finally, we solve for a combination of the Vs and Vv potentials, when both potentials are linearly confining and Vv has a color Coulombic component. We establish when these potentials give a vanishing spin?orbit interaction (as is approximately the case in quark models of the baryonic spectrum).
Two-loop superstrings IV: The cosmological constant and modular forms

Abstract The slice-independent gauge-fixed superstring chiral measure in genus 2 derived in the earlier papers of this series for each spin structure is evaluated explicitly in terms of theta-constants. The slice-independence allows an arbitrary choice of superghost insertion points q1,q2 in the explicit evaluation, and the most effective one turns out to be the split gauge defined by Sδ(q1,q2)=0. This results in expressions involving bilinear theta-constants M . The final formula in terms of only theta-constants follows from new identities between M and theta-constants which may be interesting in their own right. The action of the modular group Sp(4, Z ) is worked out explicitly for the contribution of each spin structure to the superstring chiral measure. It is found that there is a unique choice of relative phases which insures the modular invariance of the full chiral superstring measure, and hence a unique way of implementing the GSO projection for even spin structure. The resulting cosmological constant vanishes, not by a Riemann identity, but rather by the genus 2 identity expressing any modular form of weight 8 as the square of a modular form of weight 4. The degeneration limits for the contribution of each spin structure are determined, and the divergences, before the GSO projection, are found to be the ones expected on physical grounds.
The limiting spectral distribution in terms of spectral density

For a large class of symmetric random matrices with correlated entries, selected from stationary random fields of centered and square integrable variables, we show that the limiting distribution of eigenvalue counting measure always exists and we describe it via an equation satisfied by its Stieltjes transform. No rate of convergence to zero of correlations is imposed, therefore the process is allowed to have long memory. In particular, if the symmetrized matrices are constructed from stationary Gaussian random fields which have spectral density, the result of this paper gives a complete solution to the limiting eigenvalue distribution. More generally, for matrices whose entries are functions of independent and identically distributed random variables the result also holds.
Teaching an Old Ball New Tricks: Another Look at Energetics, Motion Detectors, and a Bouncing Rubber Ball.

Abouncing rubber ball under a motion sensor is a classic of introductory physics labs. It is often used to measure the acceleration due to gravity, and can also demonstrate conservation of energy. By observing that the ball rises to a lower height upon each bounce, posing the question “What is the main source of energy loss?” and requiring students to construct their own measured values for velocity from position data, a rich lab experience can be created that results in good student discussions of proper analysis of data and implementation of models. The payoff is student understanding that seemingly small differences in definitions can lead to very different conclusions.
Initial stage of cavitation in liquids and its observation by Rayleigh scattering

A theory is developed for the initial stage of cavitation in the framework of Zel'dovich–Fisher theory of nucleation in the field of negative pressure, while taking into account the surface tension dependence on the nanopore radius. A saturation mechanism is proposed that limits the exponential dependence of the nucleation rate on the energy required to create nanopores. An estimate of the saturated density of nanopores at the nucleation stage is obtained. It is shown that Rayleigh scattering can detect nanopores arising at the initial stage of cavitation development.
Near-horizon BMS symmetries as fluid symmetries

The Bondi-van der Burg-Metzner-Sachs (BMS) group is the asymptotic symmetry group of asymptotically flat gravity. Recently, Donnay et al. have derived an analogous symmetry group acting on black hole event horizons. For a certain choice of boundary conditions, it is a semidirect product of Diff(S 2), the smooth diffeomorphisms of the twosphere, acting on C ∞(S 2), the smooth functions on the two-sphere. We observe that the same group appears in fluid dynamics as symmetries of the compressible Euler equations. We relate these two realizations of Diff(S 2) ⋉ C ∞(S 2) using the black hole membrane paradigm. We show that the Lie-Poisson brackets of membrane paradigm fluid charges reproduce the near-horizon BMS algebra. The perspective presented here may be useful for understanding the BMS algebra at null infinity.
COLD FRONTS AND GAS SLOSHING IN GALAXY CLUSTERS WITH ANISOTROPIC THERMAL CONDUCTION

Cold fronts in cluster cool cores should be erased on short timescales by thermal conduction, unless protected by magnetic fields that are 'draped' parallel to the front surfaces, suppressing conduction perpendicular to the sloshing fronts. We present a series of MHD simulations of cold front formation in the core of a galaxy cluster with anisotropic thermal conduction, exploring a parameter space of conduction strengths parallel and perpendicular to the field lines. Including conduction has a strong effect on the temperature distribution of the core and the appearance of the cold fronts. Though magnetic field lines are draping parallel to the front surfaces, preventing conduction directly across them, the temperature jumps across the fronts are nevertheless reduced. The geometry of the field is such that the cold gas below the front surfaces can be connected to hotter regions outside via field lines along directions perpendicular to the plane of the sloshing motions and along sections of the front that are not perfectly draped. This results in the heating of this gas below the front on a timescale of a Gyr, but the sharpness of the density and temperature jumps may nevertheless be preserved. By modifying the gas density distribution below themore » front, conduction may indirectly aid in suppressing Kelvin-Helmholtz instabilities. If conduction along the field lines is unsuppressed, we find that the characteristic sharp jumps seen in Chandra observations of cold front clusters do not form. Therefore, the presence of cold fronts in hot clusters is in contradiction with our simulations with full Spitzer conduction. This suggests that the presence of cold fronts in hot clusters could be used to place upper limits on conduction in the bulk of the intracluster medium. Finally, the combination of sloshing and anisotropic thermal conduction can result in a larger flux of heat to the core than either process in isolation. While still not sufficient to prevent a cooling catastrophe in the very central (r {approx} 5 kpc) regions of the cool core (where something else is required, such as active galactic nucleus feedback), it reduces significantly the mass of gas that experiences a cooling catastrophe outside those small radii.« less
Contextual Text Style Transfer

We introduce a new task, Contextual Text Style Transfer - translating a sentence into a desired style with its surrounding context taken into account. This brings two key challenges to existing style transfer approaches: (I) how to preserve the semantic meaning of target sentence and its consistency with surrounding context during transfer; (ii) how to train a robust model with limited labeled data accompanied by context. To realize high-quality style transfer with natural context preservation, we propose a Context-Aware Style Transfer (CAST) model, which uses two separate encoders for each input sentence and its surrounding context. A classifier is further trained to ensure contextual consistency of the generated sentence. To compensate for the lack of parallel data, additional self-reconstruction and back-translation losses are introduced to leverage non-parallel data in a semi-supervised fashion. Two new benchmarks, Enron-Context and Reddit-Context, are introduced for formality and offensiveness style transfer. Experimental results on these datasets demonstrate the effectiveness of the proposed CAST model over state-of-the-art methods across style accuracy, content preservation and contextual consistency metrics.
Moment-Matching-Based Conjugacy Approximation for Bayesian Ranking and Selection

We study the conjugacy approximation models in the context of Bayesian ranking and selection with unknown correlations. Under the assumption of normal-inverse-Wishart prior distribution, the posterior distribution remains a normal-inverse-Wishart distribution thanks to the conjugacy property when all alternatives are sampled at each step. However, this conjugacy property no longer holds if only one alternative is sampled at a time, an appropriate setting when there is a limited budget on the number of samples. We propose two new conjugacy approximation models based on the idea of moment matching. Both of them yield closed-form Bayesian prior updating formulas. We apply these updating formulas in Bayesian ranking and selection using the knowledge gradient method and show the superiority of the proposed conjugacy approximation models in applications of wind farm placement and computer model calibration.
Characterizing the Stellar Population of NGC 1980

NGC 1980 is a young cluster that is located about 0.5 degrees south of the Orion Nebula Cluster (ONC). Recent studies by Bouy et al. and Pillitteri et al. have suggested that NGC 1980 contains an older population of stars compared to a much younger ONC, and that it belongs to a foreground population that may be located in front of the Orion A molecular gas by as much as 40 pc. In this work we present low-resolution spectra towards 148 young stars found towards the NGC 1980 region. We determine the spectral types of these stars, examine accretion signatures and measure the extinction towards them. We determine that based on these observations, the age of the population of NGC 1980 is indistinguishable from L1641, estimated to be ~3 Myr, comparable with the study by Fang et al.
Closed surface bundles of least volume

Since the set of volumes of hyperbolic 3–manifolds is well ordered, for each fixed g there is a genus–g surface bundle over the circle of minimal volume. Here, we introduce an explicit family of genus–g bundles which we conjecture are the unique such manifolds of minimal volume. Conditional on a very plausible assumption, we prove that this is indeed the case when g is large. The proof combines a soft geometric limit argument with a detailed Neumann–Zagier asymptotic formula for the volumes of Dehn fillings.
SET-ASIDES AND SUBSIDIES IN AUCTIONS

Abstract Set-asides and subsidies are used extensively in government procurement and resource sales. We analyze these policies in an empirical model of US Forest Service timber auctions. The model ...
The Low-Mass Companion to the Lithium-Depleted, Spectroscopic Binary HBC 425 (St 34)

We present high angular resolution, near-infrared imaging, and spectroscopy of a low-mass companion to the lithium-depleted, double-line spectroscopic binary HBC 425 (St 34) obtained using NIRSPEC and the Keck II adaptive optics system. Positioned ~1.23'' southeast of the primary pair, the companion, HBC 425C, is ~2.4 mag fainter at 2.2 μm. Moderate-resolution (R ~ 2500) J- and K-band spectroscopy reveals HBC 425C to have an M5.5 (± 0.5) spectral type. Comparisons with pre-main-sequence evolutionary models imply a mass of ~0.09 M⊙ and ages of 8-10 Myr, assuming the nominal distance of Taurus-Auriga (~140 pc), or ~25 Myr if placed at ~90 pc. We also present high-dispersion optical spectra of HBC 425 and HBC 425C obtained using the high-resolution echelle spectrometer (HIRES) on Keck I. We detect strong Li i λ6708 absorption in the spectrum of HBC 425C. Using curves of growth for the Li i λ6708 doublet, we estimate its abundance level to lie between log N(Li) = 1.9 and 3.1 dex. The spectrum of HBC 425 exhibits Ca ii H and K lines, He i λλ5876, 6678, and strong Balmer line emission, consistent with accretion. We place more restrictive upper limits on the surface abundance of lithium and find that HBC 425 retains less than ~0.1% of its primordial abundance. The presence of lithium in the photosphere of HBC 425C does not resolve the discrepancy between isochronal and lithium-depletion ages for the primary pair. However, if lithium were depleted relative to interstellar abundance levels, even minimally, considerable support would be gained for the more advanced age of this hierarchical triple system.
Is a simple collisionless relic dark matter particle ruled out

The central densities of dark matter (DM) halos are much lower than predicted in cold DM models of structure formation. Confirmation that they have cores with a finite central density would allow us to rule out many popular types of collisionless particles as candidates for DM. Any model that leads to cusped halos (such as cold DM) is already facing serious difficulties on small scales, and hot DM models have been excluded. Here I show that fermionic warm DM is inconsistent with the wide range of phase-space densities in the DM halos of well-observed nearby galaxies.
PHYSICAL ORIGIN OF DIFFERENCES AMONG VARIOUS MEASURES OF SOLAR MERIDIONAL CIRCULATION

We show that systematic differences between surface Doppler and magnetic element tracking measures of solar meridional flow can be explained by the effects of surface turbulent magnetic diffusion. Feature-tracking speeds are lower than plasma speeds in low and mid latitudes, because magnetic diffusion opposes poleward plasma flow in low latitudes whereas it adds to plasma flow at high latitudes. Flux-transport dynamo models must input plasma flow; the model outputs yield estimates of the surface magnetic feature tracking speed. We demonstrate that the differences between plasma speed and magnetic pattern speed in a flux-transport dynamo are consistent with the observed difference between these speeds.
Quasi-isometric classification of graph manifold groups

We show that the fundamental groups of any two closed irreducible nongeometric graph manifolds are quasi-isometric. We also classify the quasi-isometry types of fundamental groups of graph manifolds with boundary in terms of certain finite twocolored graphs. A corollary is the quasi-isometric classification of Artin groups whose presentation graphs are trees. In particular, any two right-angled Artin groups whose presentation graphs are trees of diameter greater than 2 are quasi-isometric; further, this quasi-isometry class does not include any other right-angled Artin groups. A finitely generated group can be considered geometrically when endowed with a word metric. Up to quasi-isometric equivalence, such metrics are unique. (In this article, only finitely generated groups are considered.) Given a collection of groups G, Gromov [11] proposed the fundamental questions of identifying which groups are quasi-isometric to those in G (rigidity) and which groups in G are quasi-isometric to each other (classification). In this article, we focus on the classification question for graph manifold groups and right-angled Artin groups. A compact 3-manifold M is called geometric if M\∂M admits a geometric structure in the sense of Thurston (i.e., a complete locally homogeneous Riemannian metric of finite volume). Thurston’s geometrization conjecture (see [29], [17], [21], [23], [22]) provides that every irreducible 3-manifold of zero Euler characteristic (i.e., with boundary consisting only of tori and Klein bottles) admits a decomposition along tori and Klein bottles into geometric pieces, the minimal such decomposition being called the geometric decomposition. There is a considerable literature on quasi-isometric rigidity and classification of 3-manifold groups. The rigidity results can be briefly summarized in the following form.
AN EFFICIENT, COMPACT, AND VERSATILE FIBER DOUBLE SCRAMBLER FOR HIGH PRECISION RADIAL VELOCITY INSTRUMENTS

We present the design and test results of a compact optical fiber double-scrambler for high-resolution Doppler radial velocity instruments. This device consists of a single optic: a high-index n ∼ 2 ball lens that exchanges the near and far fields between two fibers. When used in conjunction with octagonal fibers, this device yields very high scrambling gains (SGs) and greatly desensitizes the fiber output from any input illumination variations, thereby stabilizing the instrument profile of the spectrograph and improving the Doppler measurement precision. The system is also highly insensitive to input pupil variations, isolating the spectrograph from telescope illumination variations and seeing changes. By selecting the appropriate glass and lens diameter the highest efficiency is achieved when the fibers are practically in contact with the lens surface, greatly simplifying the alignment process when compared to classical double-scrambler systems. This prototype double-scrambler has demonstrated significant performance gains over previous systems, achieving SGs in excess of 10,000 with a throughput of ∼87% using uncoated Polymicro octagonal fibers. Adding a circular fiber to the fiber train further increases the SG to >20,000, limited by laboratory measurement error. While this fiber system is designed for the Habitable-zone Planet Finder spectrograph, it is more generally applicable to other instruments in the visible and near-infrared. Given the simplicity and low cost, this fiber scrambler could also easily be multiplexed for large multi-object instruments.
Multiwavelength Observations of Massive Stellar Cluster Candidates in the Galaxy

The Galaxy appears to be richer in young, massive stellar clusters than previously known, due to advances in infrared surveys that have uncovered deeply embedded regions of star formation. Young, massive clusters can significantly impact the surrounding interstellar medium (ISM) and hence radio observations can also be an important tracer of their activity. Several hundred cluster candidates are now known by examining survey data. Here, we report on multiwavelength observations of six of these candidates in the Galaxy. We carried out 4.9 and 8.5 GHz Very Large Array observations of the radio emission associated with these clusters to obtain the physical characteristics of the surrounding gas, including the Lyman continuum photon flux and ionized gas mass. Spitzer Infrared Array Camera observations were also made of these regions, and provide details on the stellar population as well as the dust continuum and polycyclic aromatic hydrocarbon emission. When compared to the known young, massive clusters in the Galaxy, the six cluster candidates have less powerful Lyman ionizing fluxes and ionize less of the H II mass in the surrounding ISM. Therefore, these cluster candidates appear to be more consistent with intermediate-mass clusters (10{sup 3}-10{sup 4} M{sub Sun }).
Inverse Depolarization: A Potential Probe of Internal Faraday Rotation and Helical Magnetic Fields in Extragalactic Radio Jets

Motivated by recent observations that show increasing fractional linear polarization with increasing wavelength in a small number of optically thin jet features, i.e., "inverse depolarization," we present a physical model that can explain this effect and may provide a new and complementary probe of the low-energy particle population and possible helical magnetic fields in extragalactic radio jets. In our model, structural inhomogeneities in the jet magnetic field create cancellation of polarization along the line of sight. Internal Faraday rotation, which increases like wavelength squared, acts to align the polarization from the far and near sides of the jet, leading to increased polarization at longer wavelengths. Structural inhomogeneities of the right type are naturally produced in helical magnetic fields and will also appear in randomly tangled magnetic fields. We explore both alternatives and find that, for random fields, the length scale for tangling cannot be too small a fraction of the jet diameter and still be consistent with the relatively high levels of fractional polarization observed in these features. We also find that helical magnetic fields naturally produce transverse structure for inverse depolarization which may be observable even in partially resolved jets.
Information Graph Flow: A Geometric Approximation of Quantum and Statistical Systems

Given a quantum (or statistical) system with a very large number of degrees of freedom and a preferred tensor product factorization of the Hilbert space (or of a space of distributions) we describe how it can be approximated with a very low-dimensional field theory with geometric degrees of freedom. The geometric approximation procedure consists of three steps. The first step is to construct weighted graphs (we call information graphs) with vertices representing subsystems (e.g., qubits or random variables) and edges representing mutual information (or the flow of information) between subsystems. The second step is to deform the adjacency matrices of the information graphs to that of a (locally) low-dimensional lattice using the graph flow equations introduced in the paper. (Note that the graph flow produces very sparse adjacency matrices and thus might also be used, for example, in machine learning or network science where the task of graph sparsification is of a central importance.) The third step is to define an emergent metric and to derive an effective description of the metric and possibly other degrees of freedom. To illustrate the procedure we analyze (numerically and analytically) two information graph flows with geometric attractors (towards locally one- and two-dimensional lattices) and metric perturbations obeying a geometric flow equation. Our analysis also suggests a possible approach to (a non-perturbative) quantum gravity in which the geometry (a secondary object) emerges directly from a quantum state (a primary object) due to the flow of the information graphs.
An analogue of a formula for Chebotarev densities

In this paper, we show an analogue of Dawsey’s formula on Chebotarev densities for finite Galois extensions of ℚ with respect to the Riemann zeta function ζ(ms) for any integer m ≥ 2. Her formula m...
THE EXTRAGALACTIC BACKGROUND LIGHT FROM THE MEASUREMENTS OF THE ATTENUATION OF HIGH-ENERGY GAMMA-RAY SPECTRUM

The attenuation of high-energy gamma-ray spectrum due to the electron-positron pair production against the extragalactic background light (EBL) provides an indirect method to measure the EBL of the universe. We use the measurements of the absorption features of the gamma-rays from blazars as seen by the Fermi Gamma-ray Space Telescope to explore the EBL flux density and constrain the EBL spectrum, star formation rate density (SFRD), and photon escape fraction from galaxies out to z = 6. Our results are basically consistent with the existing determinations of the quantities. We find a larger photon escape fraction at high redshifts, especially at z = 3, compared to the result from recent Ly? measurements. Our SFRD result is consistent with the data from both gamma-ray burst and ultraviolet (UV) observations in the 1? level. However, the average SFRD we obtain at z 3 matches the gamma-ray data better than the UV data. Thus our SFRD result at z 6 favors the fact that star formation alone is sufficiently high enough to reionize the universe.
Tidal Dissipation in WASP-12

WASP-12 is a hot Jupiter system with an orbital period of $P= 1.1\textrm{ day}$, making it one of the shortest-period giant planets known. Recent transit timing observations by Maciejewski et al. (2016) and Patra et al. (2017) find a decreasing period with $P/|\dot{P}| = 3.2\textrm{ Myr}$. This has been interpreted as evidence of either orbital decay due to tidal dissipation or a long term oscillation of the apparent period due to apsidal precession. Here we consider the possibility that it is orbital decay. We show that the parameters of the host star are consistent with either a $M_\ast \simeq 1.3 M_\odot$ main sequence star or a $M_\ast \simeq 1.2 M_\odot$ subgiant. We find that if the star is on the main sequence, the tidal dissipation is too inefficient to explain the observed $\dot{P}$. However, if it is a subgiant, the tidal dissipation is significantly enhanced due to nonlinear wave breaking of the dynamical tide near the star's center. The subgiant models have a tidal quality factor $Q_\ast'\simeq 2\times10^5$ and an orbital decay rate that agrees well with the observed $\dot{P}$. It would also explain why the planet survived for $\simeq 3\textrm{ Gyr}$ while the star was on the main sequence and yet is now inspiraling on a 3 Myr timescale. Although this suggests that we are witnessing the last $\sim 0.1\%$ of the planet's life, the probability of such a detection is a few percent given the observed sample of $\simeq 30$ hot Jupiters in $P 1.2 M_\odot$ hosts.
Perfect Packings in Quasirandom Hypergraphs II

For each of the notions of hypergraph quasirandomness that have been studied, we identify a large class of hypergraphs F so that every quasirandom hypergraph H admits a perfect F -packing. An informal statement of a special case of our general result for 3-uniform hypergraphs is as follows. Fix an integer r ⩾ 4 and 0 p H is an n -vertex triple system with r | n and the following two properties: • for every graph G with V ( G ) = V ( H ), at least p proportion of the triangles in G are also edges of H , • for every vertex x of H , the link graph of x is a quasirandom graph with density at least p . Then H has a perfect K r (3) -packing. Moreover, we show that neither of the hypotheses above can be weakened, so in this sense our result is tight. A similar conclusion for this special case can be proved by Keevash's Hypergraph Blow-up Lemma, with a slightly stronger hypothesis on H .
Harmonic Oscillator Trap and the Phase-Shift Approximation

The energy-spectrum of two point-like particles interacting in a 3-D isotropic Harmonic Oscillator (H.O.) trap is related to the free scattering phase-shifts \(\delta \) of the particles by a formula first published by Busch et al. It is here used to find an expression for the shift of the energy levels, caused by the interaction, rather than the perturbed spectrum itself. In the limit of high energy (large quantum number \(n\) of the H.O.) this shift (in H.O. units) is shown to be given by \(\Delta =-2\frac{\delta }{\pi }\), also exact in the limit of infinite scattering length (\(\delta =\pm \frac{\pi }{2}\)) in which case \(\Delta =\mp 1\). Numerical investigation shows that this expression otherwise differs from the exact result of Busch et al., by less than \(\frac{1}{2}\,\%\) except for \(n=0\) when it can be as large as \(\approx \)2.5 %. This result for the energy-shift is well known from another exactly solvable model, namely that of two particles interacting in a spherical infinite square-well trap (or box) of radius \(R\) in the limit \(R\rightarrow \infty \), and/or in the limit of large energy. It is in solid state physics referred to as Fumi’s theorem. It can be (and has been) used in (infinite) nuclear matter calculations to calculate the two-body effective interaction in situations where in-medium effects can be neglected. It is in this context referred to as the phase-shift approximation a term also used throughout this report.
Dependence of Biological Activity on the Surface Water Fraction of Planets

One of the unique features associated with the Earth is that the fraction of its surface covered by land is comparable to that spanned by its oceans and other water bodies. Here, we investigate how extraterrestrial biospheres depend on the ratio of the surficial land and water fractions. We find that worlds that are overwhelmingly dominated by landmasses or oceans are likely to have sparse biospheres. Our analysis suggests that major evolutionary events such as the buildup of O$_2$ in the atmosphere and the emergence of technological intelligence might be relatively feasible only on a small subset of worlds with surface water fractions ranging approximately between $30\%$ and $90\%$. We also discuss how our predictions can be evaluated by future observations, and the implications for the prevalence of microbial and technological species in the Universe.
Gauge-mediated supersymmetry breaking within the dynamical messenger sector

We consider the idea of combining the supersymmetry breaking and messenger sectors in models of gauge-mediated supersymmetry breaking. We discuss the advantages and problems of such models, and present an existence proof by constructing an explicit example. We explore in some detail the low-energy supersymmetry-breaking dynamics and the generation of supersymmetry-breaking soft masses of the standard model superpartners, and discuss many features which are likely to be shared by more realistic models with dynamical messengers.
Statistical Mechanics of Thin Spherical Shells

Scientists explore how thermal fluctuations affect the mechanics of thin amorphous spherical shells.
Light-state dominance from the conformal bootstrap

We derive forms of light-state dominance for correlators in CFTd, making precise the sense in which correlators can be approximated by the contribution of light operator exchanges. Our main result is that the four-point function of operators with dimension Δ is approximated, with bounded error, by the contribution of operators with scaling dimension below Δc > 2Δ in the appropriate OPE channel. Adapting an existing modular invariance argument, we use crossing symmetry to show that the heavy-state contribution is suppressed by a relative factor of $$ {e}^{2\varDelta -{\varDelta}_c} $$ . We extend this result to the first sheet and derivatives of the correlator. Further exploiting technical similarities between crossing and modular invariance, we prove analogous results for the 2d partition function along the way. We then turn to effective field theory in gapped theories and AdS/CFT, and make some general comments about the effect of integrating out heavy particles in the bulk. Combining our bounds with the Lorentzian OPE inversion formula we show that, under certain conditions, light-state dominance implies that integrating out heavy exchanges leads to higher-derivative couplings suppressed at large Δgap.
Noncompact manifolds that are inward tame

We continue our study of ends of non-compact manifolds, with a focus on the inward tameness condition. For manifolds with compact boundary, inward tameness, has significant implications. For example, such manifolds have stable homology at infinity in all dimensions. We show that these manifolds have 'almost perfectly semistable' fundamental group at each end. That observation leads to further analysis of group theoretic conditions at infinity, and to the notion of a 'near pseudo-collar' structure. We obtain a complete characterization of n-manifolds (n>5) admitting such a structure, thereby generalizing earlier work. We also construct examples illustrating the necessity and usefulness of new conditions introduced here. Variations on the notion of a perfect group, with corresponding versions of the Quillen Plus Construction, form an underlying theme.
KEN WILSON — THE EARLY YEARS

Ken Wilson's lifetime achievements in fundamental theoretical physics are well known and are well documented in this memorial volume. Therefore, there is no purpose in my adding yet another appreciation of his seminal work. Rather, I shall describe Ken and some of his activities at the beginning of his career, when he was junior faculty at Cornell and I was his student — one of two in the first cohort of PhDs that he mentored. (The other was Gerald Estberg, long time faculty and now retired at the University of San Diego.)
Structural and Ferromagnetic Properties of an Orthorhombic Phase of MnBi Stabilized with Rh Additions

Powerful electric motors like those in hybrid vehicles require strong permanent magnets, mostly based on rare-earth metals that are expensive and of uncertain production and supply. The family of manganese-bismuth compounds has been an attractive, but unstable, alternative---until now. The authors manage to stabilize a member of this family by alloying, showing a viable route for developing this class of rare-earth-free magnets.
On a Convex Embedding of the Euler Problem of Two Fixed Centers

In this article, we study a convex embedding for the Euler problem of two fixed centers for energies below the critical energy level. We prove that the doubly-covered elliptic coordinates provide a 2-to-1 symplectic embedding such that the image of the bounded component near the lighter primary of the regularized Euler problem is convex for any energy below the critical Jacobi energy. This holds true if the two primaries have equal mass, but does not hold near the heavier body.
Heat meets light on the nanoscale

We discuss the state-of-the-art and remaining challenges in the fundamental understanding and technology development for controlling light-matter interactions in nanophotonic environments in and away from thermal equilibrium. The topics covered range from the basics of the thermodynamics of light emission and absorption, to applications in solar-thermal energy generation, thermophotovoltaics, optical refrigeration, personalized cooling technologies, development of coherent incandescent light sources, and spinoptics.
Fog Data: Enhancing Telehealth Big Data Through Fog Computing

The size of multi-modal, heterogeneous data collected through various sensors is growing exponentially. It demands intelligent data reduction, data mining and analytics at edge devices. Data compression can reduce the network bandwidth and transmission power consumed by edge devices. This paper proposes, validates and evaluates Fog Data, a service-oriented architecture for Fog computing. The center piece of the proposed architecture is a low power embedded computer that carries out data mining and data analytics on raw data collected from various wearable sensors used for telehealth applications. The embedded computer collects the sensed data as time series, analyzes it, and finds similar patterns present. Patterns are stored, and unique patterns are transmited. Also, the embedded computer extracts clinically relevant information that is sent to the cloud. A working prototype of the proposed architecture was built and used to carry out case studies on telehealth big data applications. Specifically, our case studies used the data from the sensors worn by patients with either speech motor disorders or cardiovascular problems. We implemented and evaluated both generic and application specific data mining techniques to show orders of magnitude data reduction and hence transmission power savings. Quantitative evaluations were conducted for comparing various data mining techniques and standard data compression techniques. The obtained results showed substantial improvement in system efficiency using the Fog Data architecture.
The Hidden Subgroup Problem for Universal Algebras

The Hidden Subgroup Problem (HSP) is a computational problem which includes as special cases integer factorization, the discrete logarithm problem, graph isomorphism, and the shortest vector problem. The celebrated polynomial-time quantum algorithms for factorization and the discrete logarithm are restricted versions of a generic polynomial-time quantum solution to the HSP for abelian groups, but despite focused research no polynomial-time solution for general groups has yet been found. We propose a generalization of the HSP to include arbitrary algebraic structures and analyze this new problem on powers of 2-element algebras. We prove a complete classification of every such power as quantum tractable (i.e. polynomial-time), classically tractable, quantum intractable, or classically intractable. In particular, we identify a class of algebras for which the generalized HSP exhibits super-polynomial speedup on a quantum computer compared to a classical one.
Optimal Threshold Design for Quanta Image Sensor

Quanta image sensor is a binary imaging device envisioned to be the next generation image sensor after CCD and CMOS. Equipped with a massive number of single photon detectors, the sensor has a threshold $q$ above which the number of arriving photons will trigger a binary response “1”, or “0” otherwise. Existing methods in the device literature typically assume that $q = 1$ uniformly. We argue that a spatial-temporally varying threshold can significantly improve the signal-to-noise ratio of the reconstructed image. In this paper, we present an optimal threshold design framework. We make two contributions. First, we derive a set of oracle results to theoretically inform the maximally achievable performance. We show that the oracle threshold should match exactly with the underlying pixel intensity. Second, we show that around the oracle threshold there exists a set of thresholds that give asymptotically unbiased reconstructions. The asymptotic unbiasedness has a phase transition behavior which allows us to develop a practical threshold update scheme using a bisection method. Experimentally, the new threshold design method achieves better rate of convergence than existing methods.
Fermi surface pockets in electron-doped iron superconductor by Lifshitz transition

The Fermi surface pockets that lie at the corner of the two-iron Brillouin zone in heavily electron-doped iron selenide superconductors are accounted for by an extended Hubbard model over the square lattice of iron atoms that includes the principal 3d xz and 3d yz orbitals. At half filling, and in the absence of intra-orbital next-nearest neighbor hopping, perfect nesting between electron-type and hole-type Fermi surfaces at the the center and at the corner of the one-iron Brillouin zone is revealed. It results in hidden magnetic order in the presence of magnetic frustration within mean field theory. An Eliashberg-type calculation that includes spin-fluctuation exchange finds that the Fermi surfaces undergo a Lifshitz transition to electron/hole Fermi surface pockets centered at the corner of the two-iron Brillouin zone as on-site repulsion grows strong. In agreement with angle-resolved photoemission spectroscopy on iron selenide high-temperature superconductors, only the two electron-type Fermi surface pockets remain after a rigid shift in energy of the renormalized band structure by strong enough electron doping. At the limit of strong on-site repulsion, a spin-wave analysis of the hidden-magnetic-order state finds a 'floating ring' of low-energy spin excitations centered at the checkerboard wavenumber . This prediction compares favorably with recent observations of low-energy spin resonances around (π, π) in intercalated iron selenide by inelastic neutron scattering.