cssi/SciSciGPT-SciSciNet huggingface dataset:
FJRW-Rings and Mirror Symmetry

The Landau-Ginzburg Mirror Symmetry Conjecture states that for an invertible quasi-homogeneous singularity W and its maximal group G of diagonal symmetries, there is a dual singularity WT such that the orbifold A-model of W/G is isomorphic to the B-model of WT. The Landau-Ginzburg A-model is the Frobenius algebra \({\fancyscript{H}_{W,G}}\) constructed by Fan, Jarvis, and Ruan, and the B-model is the orbifold Milnor ring of WT. We verify the Landau-Ginzburg Mirror Symmetry Conjecture for Arnol’d’s list of unimodal and bimodal quasi-homogeneous singularities with G the maximal diagonal symmetry group, and include a discussion of eight axioms which facilitate the computation of FJRW-rings.
Quantum Gravity as a Fermi Liquid

We present a reformulation of loop quantum gravity with a cosmological constant and no matter as a Fermi-liquid theory. When the topological sector is deformed and large gauge symmetry is broken, we show that the Chern–Simons state reduces to Jacobson’s degenerate sector describing 1+1 dimensional propagating fermions with nonlocal interactions. The Hamiltonian admits a dual description which we realize in the simple BCS model of superconductivity. On one hand, Cooper pairs are interpreted as wormhole correlations at the de Sitter horizon; their number yields the de Sitter entropy. On the other hand, BCS is mapped into a deformed conformal field theory reproducing the structure of quantum spin networks. When area measurements are performed, Cooper-pair insertions are activated on those edges of the spin network intersecting the given area, thus providing a description of quantum measurements in terms of excitations of a Fermi sea to superconducting levels. The cosmological constant problem is naturally addressed as a nonperturbative mass-gap effect of the true Fermi-liquid vacuum.
Belief propagation and loop series on planar graphs

We discuss a generic model of Bayesian inference with binary variables defined on edges of a planar graph. The Loop Calculus approach of Chertkov and Chernyak (2006 Phys. Rev. E 73 065102(R) [cond-mat/0601487]; 2006 J. Stat. Mech. P06009 [cond-mat/0603189]) is used to evaluate the resulting series expansion for the partition function. We show that, for planar graphs, truncating the series at single-connected loops reduces, via a map reminiscent of the Fisher transformation (Fisher 1961 Phys. Rev. 124 1664), to evaluating the partition function of the dimer-matching model on an auxiliary planar graph. Thus, the truncated series can be easily re-summed, using the Pfaffian formula of Kasteleyn (1961 Physics 27 1209). This allows us to identify a big class of computationally tractable planar models reducible to a dimer model via the Belief Propagation (gauge) transformation. The Pfaffian representation can also be extended to the full Loop Series, in which case the expansion becomes a sum of Pfaffian contributions, each associated with dimer matchings on an extension to a subgraph of the original graph. Algorithmic consequences of the Pfaffian representation, as well as relations to quantum and non-planar models, are discussed.
Radius-to-frequency Mapping and FRB Frequency Drifts

We build a model of radius-to-frequency mapping in magnetospheres of neutron stars and apply it to frequency drifts observed in Fast Radio Bursts. We assume that an emission patch propagates along the dipolar magnetic field lines producing coherent emission with frequency, direction and polarization defined by the local magnetic field. The observed temporal evolution of the frequency depends on relativistic effects of time contraction and the curvature of the magnetic field lines. The model generically produces linear scaling of the drift rate, $\dot{\omega} \propto - \omega$, matching both numerically and parametrically the rates observed in FBRs; a more complicated behavior of $\dot{\omega} $ is also possible. Fast rotating magnetospheres produce higher drifts rates for similar viewing parameters than the slowly rotating ones. In the case of repeaters same source may show variable drift pattens depending on the observing phase. We expect rotational of polarization position angle through a burst, though by smaller amount than in radio pulsars. All these findings compare favorably with properties of FBRs, strengthening their possible loci in the magnetospheres of neutron stars.
Homogeneous 3-Dimensional Permutation Structures

We provide a classification of the homogeneous 3-dimensional permutation structures, i.e. homogeneous structures in a language of 3 linear orders, partially answering a 2002 question of Cameron. We also arrive at a natural description of all known homogeneous finite-dimensional permutation structures by modifying the language used in the construction from [Samuel Braunfeld, Electronic Journal of Combinatorics, 2016], completing the catalog begun there.
Bi-stochastic kernels via asymmetric affinity functions

Abstract In this short letter we present the construction of a bi-stochastic kernel p for an arbitrary data set X that is derived from an asymmetric affinity function α. The affinity function α measures the similarity between points in X and some reference set Y. Unlike other methods that construct bi-stochastic kernels via some convergent iteration process or through solving an optimization problem, the construction presented here is quite simple. Furthermore, it can be viewed through the lens of out of sample extensions, making it useful for massive data sets.
A dispersion relation for the density of states with application to the Casimir effect

Abstract The trace of a function of a Schrodinger operator minus the same for the Laplacian can be expressed in terms of the determinant of its scattering matrix. The naive formula for this determinant is divergent. Using a dispersion relation, we find another expression for it which is convergent, but needs one piece of information beyond the scattering matrix: the spatial integral of the potential. Except for this ‘anomaly’, we can express the Casimir energy of a compact body in terms of its optical scattering matrix, without assuming any rotational symmetry for its shape.
STRUCTURE COMPUTATION AND DISCRETE LOGARITHMS IN FINITE ABELIAN p-GROUPS

We present a generic algorithm for computing discrete logarithms in a finite abelian p-group H, improving the Pohlig—Hellman algorithm and its generalization to noncyclic groups by Teske. We then give a direct method to compute a basis for H without using a relation matrix. The problem of computing a basis for some or all of the Sylow p-subgroups of an arbitrary finite abelian group G is addressed, yielding a Monte Carlo algorithm to compute the structure of G using O(|G| 1/2 ) group operations. These results also improve generic algorithms for extracting pth roots in G.
Studying particle acceleration from driven magnetic reconnection at the termination shock of a relativistic striped wind using particle-in-cell simulations

A rotating pulsar creates a surrounding pulsar wind nebula (PWN) by steadily releasing an energetic wind into the interior of the expanding shockwave of supernova remnant or interstellar medium. At the termination shock of a PWN, the Poynting-flux- dominated relativistic striped wind is compressed. Magnetic reconnection is driven by the compression and converts magnetic energy into particle kinetic energy and accelerating particles to high energies. We carrying out particle-in-cell (PIC) simulations to study the shock structure as well as the energy conversion and particle acceleration mechanism. By analyzing particle trajectories, we find that many particles are accelerated by Fermi-type mechanism. The maximum energy for electrons and positrons can reach hundreds of TeV.
A Non-local Model of the Propagation of Action Potentials in Myelinated Neurons

Myelinated neurons are characterized by the presence of myelin, a multilaminated wrapping around the axons formed by specialized neuroglial cells. Myelin acts as an electrical insulator and therefore, in myelinated neurons, the action potentials do not propagate within the axons but happen only at the nodes of Ranvier which are gaps in the axonal myelination. Recent advancements in brain science have shown that the shapes, timings, and propagation speeds of these so-called saltatory action potentials are controlled by various biochemical interactions among neurons, glial cells and the extracellular space. Given the complexity of brain’s structure and processes, the work hypothesis made in this paper is that non-local effects are involved in the optimal propagation of action potentials. A non- local model of the action potentials propagation in myelinated neurons is proposed that involves spatial derivatives of fractional order. The effects of non- locality on the distribution of the membrane potential are investigated using numerical simulations.
HIGH ENERGY COSMIC RAYS, GAMMA RAYS AND NEUTRINOS FROM AGN

The author reviews a model for the emission of high energy cosmic rays, gamma-rays and neutrinos from AGN (Active Galactic Nuclei) that he has proposed since 1985. Further discussion of the knee energy phenomenon of the cosmic ray energy spectrum requires the existence of a heavy particle with mass in the knee energy range. A possible method of detecting such a particle in the Pierre Auger Project is suggested. Also presented is a relation between the spectra of neutrinos and gamma-rays emitted from AGN. This relation can be tested by high energy neutrino detectors such as ICECUBE, the Mediterranean Sea Detector and possibly by the Pierre Auger Project.
Cohomological obstruction theory for Brauer classes and the period-index problem

Let U be a connected scheme of finite ´ etale cohomological dimensi on in which every finite set of points is contained in an affine open subsch eme. Suppose that � is a class in H 2 (U´,Gm)tors. For each positive integer m, the K-theory of �-twisted sheaves is used to identify obstructions tobeing representable by an Azumaya algebra of rank m 2 . Theindex of �, denoted eti(�), is the least positive integer such that all the obstructions vanish. Let per(�) be the order of � in H 2 (U´,Gm)tors. Methods from stable homotopy theory give an upper bound on theindex that depends on the period ofand the ´ etale cohomological dimension of U ; this bound is expressed in terms of the exponents of the stable homotopy groups of spheres and the exponents of the stable homotopy groups of B (Z/(per(�))). As a corollary, if U is the spectrum of a field of finite cohomo- logical dimension d, then eti(�)jper(�) b d 2 c , where b d 2 c is the integer part of d 2 , whenever per(�) is divided neither by the characteristic of k nor by any primes that are small relative to d.
Modeling Mid-Ultraviolet Spectra. I. Temperatures of Metal-poor Stars* **

Determining the properties of remote globular clusters and elliptical galaxies using evolutionary population synthesis requires a library of reliable model stellar fluxes. Empirical libraries are limited to spectra of stars in the solar neighborhood, with nearly solar abundances and abundance ratios. We report here a rst step towards providing a flux library that includes nonsolar abundances, based on calculations from rst principles that are calibrated empirically. Because the mid-ultraviolet spectrum of an old stellar system is dominated by the contribution from its main-sequence turno stars, we have started by modeling these. We have calculated mid-ultraviolet spectra for the Sun and nine nearby, near-main-sequence stars spanning metallicities from less than 1/100 solar to greater than solar, encompassing a range of light-element abundance enhancements. We rst determined temperatures of eight of the stars by analyzing optical echelle spectra together with the mid-ultraviolet. Both could be matched at the same time only when models with no convective overshoot were adopted, and only when an approximate chromosphere was incorporated near the surface of relatively metal-rich models. Extensive modications to mid-UV line parameters were also required, notably the manual assignment of approximate identications for mid-UV lines missing from laboratory linelists. Without recourse to additional missing opacity, these measures suce to reproduce in detail almost the entire mid-UV spectrum of solar-temperature stars up to one-tenth solar metallicity, and the region from 2900 A to 3100 A throughout the entire metallicity range. Ramications for abundance determinations in individual metal-poor stars and for age-metallicity determinations of old stellar systems are briefly discussed, with emphasis on the predictive power of the calculations. 1 Based on observations obtained with the Hubble Space Telescope of Space Telescope Science Institute, under contract with the National Aeronautics and Space Administration (NASA). 2 Based on observations obtained with the Shane Telescope at Mt. Hamilton, UCO/Lick Observatory.
A Quantum Dipolar Spin Liquid

Quantum spin liquids are a class of magnetic ground states reliant on non-local entanglement. Motivated by recent advances in the control of ultracold polar molecules and the development of dipolar quantum materials, we show that dipolar interactions between S = 1/2 moments stabilize spin liquids on the triangular and kagome lattices. In the latter case, the moments spontaneously break time-reversal, forming a chiral spin liquid with robust edge modes and emergent semions. We propose a simple route toward synthesizing a dipolar Heisenberg antiferromagnet from lattice-trapped polar molecules using only a single pair of rotational states and a constant electric field. A large-scale density matrix renormalization group study of the dipolar Heisenberg model reveals evidence for quantum spin liquid ground states on both triangular and kagome lattices.
Quark model relations for b-baryon decay

Properties of b-baryon decay matrix elements (amplitudes) are derived in a nonsymmetric quark model without any use of SU(6), SU(3), or SU(2) (isotopic spin) groups. Equalities between pairs of matrix elements are derived, and $\Lambda-\Sigma$ mixing is used to calculate the branching ratio for the transition $\Lambda_b\rightarrow \Sigma^0$.
Quantifying the Effects of Prosody Modulation on User Engagement and Satisfaction in Conversational Systems

As voice-based assistants such as Alexa, Siri, and Google Assistant become ubiquitous, users increasingly expect to maintain natural and informative conversations with such systems. However, for an open-domain conversational system to be coherent and engaging, it must be able to maintain the user's interest for extended periods, without sounding "boring" or "annoying". In this paper, we investigate one natural approach to this problem of modulating response prosody, i.e., changing the pitch and cadence of the response to indicate delight, sadness or other common emotions, as well as using pre-recorded interjections. Intuitively, this approach should improve the naturalness of the conversation, but attempts to quantify the effects of prosodic modulation on user satisfaction and engagement remain challenging. To accomplish this, we report results obtained from a large-scale empirical study that measures the effects of prosodic modulation on user behavior and engagement across multiple conversation domains, both immediately aftereach turn, and at the overall conversation level. Our results indicate that the prosody modulation significantly increases both immediate and overall user satisfaction. However, since the effects vary across different domains, we verify that prosody modulations do not substitute for coherent, informative content of the responses. Together, our results provide useful tools and insights for improving the naturalness of responses in conversational systems.
2-parts of real class sizes

We investigate the structure of finite groups whose non-central real class sizes have the same $2$-part. In particular, we prove that such groups are solvable and have $2$-length one. As a consequence, we show that a finite group is solvable if it has two real class sizes. This confirms a conjecture due to G. Navarro, L. Sanus and P. Tiep.
Group incentives and rational voting

Our model describes competition between groups driven by the choices of self-interested voters within groups. Within a Poisson voting environment, parties observe aggregate support from groups and can allocate prizes or punishments to them. In a tournament style analysis, the model characterizes how contingent allocation of prizes based on relative levels of support affects equilibrium voting behavior. In addition to standard notions of pivotality, voters influence the distribution of prizes across groups. Such prize pivotality supports positive voter turnout even in non-competitive electoral settings. The analysis shows that competition for a prize awarded to the most supportive group is only stable when two groups actively support a party. However, competition among groups to avoid punishment is stable in environments with any number of groups. We conclude by examining implications for endogenous group formation and how politicians structure the allocation of rewards and punishments.
From Hardy Spaces to Quantum Jumps: a Quantum Mechanical Beginning of Time

In quantum mechanical experiments one distinguishes between the state of an experimental system and an observable measured in it. Heuristically, the distinction between states and observables is also suggested in scattering theory or when one expresses causality. We explain how this distinction can be made also mathematically. The result is a theory with asymmetric time evolution and for which decaying states are exactly unified with resonances. A consequence of the asymmetric time evolution is a beginning of time. The meaning of this beginning of time can be understood by identifying it in data from quantum jumps experiments.
A Wannier orbital based method for resonant inelastic x-ray scattering simulation

We report an algorithm for simulating oxygen K-edge RIXS for weakly correlated systems, using maximally localized Wannier functions as the basis set. The N-electron wavefunctions are formulated using single Slater determinants, and many-body effects are treated explicitly at the dipole matrix element level. The simulated results for oxygen K-edge RIXS from solid state Li2CO3 matches well with the experimental data. Aside from being efficient and reasonably accurate, this algorithm also shows potential to extend to more complex RIXS problems.
Turbulence and Mixing in the Intracluster Medium

The intracluster medium (ICM) is stably stratified in the hydrodynamic sense with the entropy s increasing outwards. However, thermal conduction along magnetic field lines fundamentally changes the stability of the ICM, leading to the “heat‐flux buoyancy instability” when dT/dr>0 and the “magnetothermal instability” when dT/dr 0 and parallel to r when dT/dr<0), without generating sustained convection. We show that after an anisotropically conducting plasma reaches this nonlinearly stable magnetic configuration, it experiences a buoyant restoring force that resists further distortions of the magnetic field. This restoring force is analogous to the buoyant restoring force experienced by a stably stratified adiabatic plasma. We argue that in order for a driving mechanism (e.g, galaxy mot...
The role of decomposition reactions in assessing first-principles predictions of solid stability

The performance of density functional theory approximations for predicting materials thermodynamics is typically assessed by comparing calculated and experimentally determined enthalpies of formation from elemental phases, ΔHf. However, a compound competes thermodynamically with both other compounds and their constituent elemental forms, and thus, the enthalpies of the decomposition reactions to these competing phases, ΔHd, determine thermodynamic stability. We evaluated the phase diagrams for 56,791 compounds to classify decomposition reactions into three types: 1. those that produce elemental phases, 2. those that produce compounds, and 3. those that produce both. This analysis shows that the decomposition into elemental forms is rarely the competing reaction that determines compound stability and that approximately two-thirds of decomposition reactions involve no elemental phases. Using experimentally reported formation enthalpies for 1012 solid compounds, we assess the accuracy of the generalized gradient approximation (GGA) (PBE) and meta-GGA (SCAN) density functionals for predicting compound stability. For 646 decomposition reactions that are not trivially the formation reaction, PBE (mean absolute difference between theory and experiment (MAD) = 70 meV/atom) and SCAN (MAD = 59 meV/atom) perform similarly, and commonly employed correction schemes using fitted elemental reference energies make only a negligible improvement (~2 meV/atom). Furthermore, for 231 reactions involving only compounds (Type 2), the agreement between SCAN, PBE, and experiment is within ~35 meV/atom and is thus comparable to the magnitude of experimental uncertainty.
Auroral radio emission from late L and T dwarfs: A new constraint on dynamo theory in the substellar regime

We have observed six late L and T dwarfs with the Karl G. Jansky Very Large Array (VLA) to investigate the presence of highly circularly polarized radio emission, associated with large-scale auroral currents. Previous surveys encompassing ~60 L6 or later targets have yielded only one detection. Our sample includes the previously detected T6.5 dwarf 2MASS 10475385+2124234, as well as five new targets selected for the presence of Hα emission and/or optical infrared photometric variability, which are possible manifestations of auroral activity. We detect 2MASS 10475385+2124234, as well as four of the five targets in our biased sample, including the strong IR-variable source SIMP J01365662+0933473 and bright Hα emitter 2MASS 12373919+6526148, reinforcing the possibility that activity at these disparate wavelengths is related. The radio emission frequency corresponds to a precise determination of the lower-bound magnetic field strength near the surface of each dwarf, and this new sample provides robust constraints on dynamo theory in the low-mass brown dwarf regime. Magnetic fields ≳2.5 kG are confirmed for five of six targets. Our results provide tentative evidence that the dynamo operating in this mass regime may be inconsistent with predicted values from a recently proposed model. Further observations at higher radio frequencies are essential for verifying this assertion.
Effects, determination, and correction of count rate nonlinearity in multi-channel analog electron detectors.

Detector counting rate nonlinearity, though a known problem, is commonly ignored in the analysis of angle resolved photoemission spectroscopy where modern multichannel electron detection schemes using analog intensity scales are used. We focus on a nearly ubiquitous “inverse saturation” nonlinearity that makes the spectra falsely sharp and beautiful. These artificially enhanced spectra limit accurate quantitative analysis of the data, leading to mistaken spectral weights, Fermi energies, and peak widths. We present a method to rapidly detect and correct for this nonlinearity. This algorithm could be applicable for a wide range of nonlinear systems, beyond photoemission spectroscopy.
Superinsulator–superconductor duality in two dimensions

Abstract For nearly a half century the dominant orthodoxy has been that the only effect of the Cooper pairing is the state with zero resistivity at finite temperatures, superconductivity. In this work we demonstrate that by the symmetry of the Heisenberg uncertainty principle relating the amplitude and phase of the superconducting order parameter, Cooper pairing can generate the dual state with zero conductivity in the finite temperature range, superinsulation. We show that this duality realizes in the planar Josephson junction arrays (JJA) via the duality between the Berezinskii–Kosterlitz–Thouless (BKT) transition in the vortex–antivortex plasma, resulting in phase-coherent superconductivity below the transition temperature, and the charge-BKT transition occurring in the insulating state of JJA and marking formation of the low-temperature charge-BKT state, superinsulation. We find that in disordered superconducting films that are on the brink of superconductor–insulator transition the Coulomb forces between the charges acquire two-dimensional character, i.e. the corresponding interaction energy depends logarithmically upon charge separation, bringing the same vortex-charge-BKT transition duality, and realization of superinsulation in disordered films as the low-temperature charge-BKT state. Finally, we discuss possible applications and utilizations of superconductivity–superinsulation duality.
Experimental Demonstration of Correlated Flux Scaling in Photoconductivity and Photoluminescence of Lead-Halide Perovskites

Despite the rapid progress in lead-halide perovskite solar cells, our understanding of the basic optoelectronic properties of these materials is still incomplete. Here the authors show a clear, universal correlation between the photoexcitation-flux dependences of photoconductivity and photoluminescence, which helps to uncover the unique photophysics of these materials. While the photoconductivity exhibits a crossover in its power law from an exponent of 1 to \textonehalf{}, the photoluminescence crosses from 2 to 1\textonehalf{}. The authors discuss phenomenological scenarios leading to this unusual situation, and propose an analytical model of competing carrier diffusion and recombination.
GAS EXCITATION IN ULIRGs: MAPS OF DIAGNOSTIC EMISSION-LINE RATIOS IN SPACE AND VELOCITY*

Emission-line spectra extracted at multiple locations across 39 ultraluminous infrared galaxies have been compiled into a spectrophotometric atlas. Line profiles of Hα, [N II], [S II], [O I], Hβ, and [O III] are resolved and fit jointly with common velocity components. Diagnostic ratios of these line fluxes are presented in a series of plots, showing how the Doppler shift, line width, gas excitation, and surface brightness change with velocity at fixed position and also with distance from the nucleus. One general characteristic of these spectra is the presence of shocked gas extending many kiloparsecs from the nucleus. In some systems, the rotation curves of the emitting gas indicate motions that suggest gas disks, which are most frequent at early merger stages. At these early merger stages, the emission line ratios indicate the presence of shocked gas, which may be triggered by the merger event. We also report the general characteristics of the integrated spectra.
Approximate Supermodularity of Kalman Filter Sensor Selection

This article considers the problem of selecting sensors in a large-scale system to minimize the error in estimating its states, more specifically, the state estimation mean-square error (MSE) and worst-case error for Kalman filtering and smoothing. Such selection problems are in general NP-hard, i.e., their solution can only be approximated in practice even for moderately large problems. Due to its low complexity and iterative nature, greedy algorithms are often used to obtain these approximations by selecting one sensor at a time choosing at each step the one that minimizes the estimation performance metric. When this metric is supermodular, this solution is guaranteed to be $(1-1/e)$ -optimal. This is, however, not the case for the MSE or the worst-case error. This issue is often circumvented by using supermodular surrogates, such as the $\log \det$ , despite the fact that minimizing the $\log \det$ is not equivalent to minimizing the MSE. Here, this issue is addressed by leveraging the concept of approximate supermodularity to derive near-optimality certificates for greedily minimizing the estimation mean-square and worst-case error. In typical application scenarios, these certificates approach the $(1-1/e)$ guarantee obtained for supermodular functions, thus demonstrating that no change to the original problem is needed to obtain guaranteed good performance.
An Evolutionary Algorithm Approach to Link Prediction in Dynamic Social Networks

Abstract Many real world, complex phenomena have underlying structures of evolving networks where nodes and links are added and removed over time. A central scientific challenge is the description and explanation of network dynamics, with a key test being the prediction of short and long term changes. For the problem of short-term link prediction, existing methods attempt to determine neighborhood metrics that correlate with the appearance of a link in the next observation period. Recent work has suggested that the incorporation of topological features and node attributes can improve link prediction. We provide an approach to predicting future links by applying the Covariance Matrix Adaptation Evolution Strategy (CMA-ES) to optimize weights which are used in a linear combination of sixteen neighborhood and node similarity indices. We examine a large dynamic social network with over 106 nodes (Twitter reciprocal reply networks), both as a test of our general method and as a problem of scientific interest in itself. Our method exhibits fast convergence and high levels of precision for the top twenty predicted links. Based on our findings, we suggest possible factors which may be driving the evolution of Twitter reciprocal reply networks.
Recoverability for Holevo's Just-as-Good Fidelity

Holevo's just-as-good fidelity is a similarity measure for quantum states that has found several applications. One of its critical properties is that it obeys a data processing inequality: the measure does not decrease under the action of a quantum channel on the underlying states. In this paper, I prove a refinement of this data processing inequality that includes an additional term related to recoverability. That is, if the increase in the measure is small after the action of a partial trace, then one of the states can be nearly recovered by the Petz recovery channel, while the other state is perfectly recovered by the same channel. The refinement is given in terms of the trace distance of one of the states to its recovered version and also depends on the minimum eigenvalue of the other state. As such, the refinement is universal, in the sense that the recovery channel depends only on one of the states, and it is explicit, given by the Petz recovery channel. Full version of this paper is accessible at arXiv:1801.02800
Dark Gauge U (1) symmetry for an alternative left–right model

An alternative left–right model of quarks and leptons, where the $$SU(2)_R$$ lepton doublet $$(\nu ,l)_R$$ is replaced with $$(n,l)_R$$ so that $$n_R$$ is not the Dirac mass partner of $$\nu _L$$ , has been known since 1987. Previous versions assumed a global $$U(1)_S$$ symmetry to allow n to be identified as a dark-matter fermion. We propose here a gauge extension by the addition of extra fermions to render the model free of gauge anomalies, and just one singlet scalar to break $$U(1)_S$$ . This results in two layers of dark matter, one hidden behind the other.
Tannakian Categories with Semigroup Actions

A theorem of Ostrowski implies that are algebraically independent over . More generally, for a linear differential or difference equation, it is an important problem to find all algebraic dependencies among a non-zero solution and particular transformations of , such as derivatives of with respect to parameters, shifts of the arguments, rescaling, etc. In this paper, we develop a theory of Tannakian categories with semigroup actions, which will be used to attack such questions in full generality, as each linear differential equation gives rise to a Tannakian category. Deligne studied actions of braid groups on categories and obtained a finite collection of axioms that characterizes such actions to apply them to various geometric constructions. In this paper, we find a finite set of axioms that characterizes actions of semigroups that are finite free products of semigroups of the form on Tannakian categories. This is the class of semigroups that appear in many applications.
The Importance of Realistic Starting Models for Hydrodynamic Simulations of Stellar Collisions

We demonstrate the necessity of using realistic stellar models taken from stellar evolution codes, as opposed to polytropes, for starting models in smoothed particle hydrodynamics calculations of collisions between main-sequence stars. Evolved stars have mean molecular weight gradients, which affect their entropy profiles and therefore affect how they react during a collision. The structure of stellar collision products of polytrope parent stars is significantly different from that of collision products of realistic parent models. These differences strongly affect the future evolution of the collision products, particularly products of collisions between unequal mass stars which have undergone significant chemical evolution. The use of polytropes as parent star models is likely to result in qualitatively mistaken results for the structure of the collision product.
Classical-quantum correspondence for fields

We map the quantum problem of a free bosonic field in a space-time dependent background into a classical problem. N degrees of freedom of a real field in the quantum theory are mapped into 2N2 classical simple harmonic oscillators with specific initial conditions. We discuss how this classical-quantum correspondence (CQC) may be used to evaluate quantum radiation and fully treat the backreaction of quantum fields on classical backgrounds. The technique has widespread application, including to the quantum evaporation of classical breathers ("oscillons").
Magnon and spin transition contribution in heat capacity of ferromagnetic Cr-doped MnTe: Experimental evidence for a paramagnetic spin-caloritronic effect

We present experimental evidence for the simultaneous existence of the magnons and spin-state transition contributions to the heat capacity in ferromagnetic (FM) Cr-doped MnTe (Tc ∼ 280 K), where the magnon heat capacity is attributed to the observed magnon-bipolar carrier-drag thermopower. The pristine antiferromagnetic (AFM) MnTe shows only a magnon-induced peak in the heat capacity near the Neel temperature, TN ∼ 307 K. However, Cr-doped MnTe shows a magnon-contributed heat capacity peak at ∼293 K with an additional peak in the deep paramagnetic domain near 780 K. Temperature-dependent magnetic susceptibility reveals that Cr-doping initially creates low-spin (LS) state Mn2+ ions into MnTe near and below TN due to a higher crystal field induced by Cr ions. Above 400 K, LS Mn2+ ions start converting into high-spin (HS) Mn2+ ions. The LS-to-HS transition of Mn2+ leads to an excess entropy and hence excess heat capacity contribution in the system. Temperature-dependent X-ray diffraction (XRD) and magnetic field-dependent susceptibility (M-H) confirmed no presence of any structural changes and magnetic polaron, respectively. Both XRD and M-H ensure that the peak of the heat capacity in the paramagnetic domain is originated solely by the spin-state transition. The heat capacity vs temperature was calculated to explain the contribution of each component, including the ones due to the phonons, magnons, spin-transition, Schottky anomaly, and lattice dilation. With the recent advances in spin-caloritronics extending the spin-based effects from magnetic to paramagnetic materials, the data from the heat capacity can play a crucial role to probe the presence of different phenomena, such as paramagnon-carrier-drag and spin-entropy thermopowers.
USING NEWTON'S LAW FOR DARK ENERGY

A model is introduced in which Newton's law is modified between matter and dark energy corpuscles (DECs). The model predicts that the DEC component is presently decelerating in its expansion at 14% of the magnitude of the matter expansion acceleration. In the future, expansion of the DEC universe will continue to decelerate.
Real-time calibration with spectator qubits

Accurate control of quantum systems requires a precise measurement of the parameters that govern the dynamics, including control fields and interactions with the environment. Parameters will drift in time and experiments interleave protocols that perform parameter estimation, with protocols that measure the dynamics of interest. Here we specialize to a system made of qubits where the dynamics correspond to a quantum computation. We propose setting aside some qubits, which we call spectator qubits, to be measured periodically during the computation, to act as probes of the changing experimental and environmental parameters. By using control strategies that minimize the sensitivity of the qubits involved in the computation, we can acquire sufficient information from the spectator qubits to update our estimates of the parameters and improve our control. As a result, we can increase the length of experiments where the dynamics of the data qubits are highly reliable. In particular, we simulate how spectator qubits can keep the error level of operations on data qubits below a 10−4 threshold in two scenarios involving coherent errors: a classical magnetic field gradient dynamically decoupled with sequences of two or four π-pulses, and laser beam instability detected via crosstalk with neighboring atoms in an ion trap.
On the quantum-mechanics of a single photon

It is shown that a Dirac(-type) equation for a rank-two bi-spinor field ψph on Minkowski (configuration) spacetime furnishes a Lorentz-covariant quantum-mechanical wave equation in position-space representation for a single free photon. This equation does not encounter any of the roadblocks that have obstructed previous attempts (by various authors) to formulate a quantum-mechanical photon wave equation. In particular, it implies that the photon wave function ψph yields conserved non-negative Born-rule-type quantum probabilities and that its probability current density four-vector transforms properly under Lorentz transformations. Moreover, the eigenvalues of the pertinent photon Dirac Hamiltonian and the vector eigenvalues of the photon momentum operator yield the familiar Einstein relations E = ℏω and p = ℏk, respectively. Furthermore, these spin-1 wave modes are automatically transversal without the need of an additional constraint on the initial data. Some comments on other proposals to set up a photon wave equation are supplied as well.
Exotic Smoothness in Four Dimensions and Euclidean Quantum Gravity

In this paper we calculate the effect of the inclusion of exotic smooth structures on typical observables in Euclidean quantum gravity. We do this in the semiclassical regime for several gravitational free-field actions and find that the results are similar, independent of the particular action that is chosen. These are the first results of their kind in dimension four, which we extend to include one-loop contributions as well. We find these topological features can have physically significant results without the need for additional exotic physics.
Astrophysical Tests of Kinematical Conformal Cosmology in Fourth-Order Conformal Weyl Gravity

In this work we analyze kinematical conformal cosmology (KCC), an alternative cosmological model based on conformal Weyl gravity (CG), and test it against current type Ia supernova (SNIa) luminosity data and other astrophysical observations. Expanding upon previous work on the subject, we revise the analysis of SNIa data, confirming that KCC can explain the evidence for an accelerating expansion of the Universe without using dark energy or other exotic components. We obtain an independent evaluation of the Hubble constant, H0 = 67:53 kms 1 Mpc 1 , very close to the current best estimates. The main KCC and CG parameters are re-evaluated and their revised values are found to be close to previous estimates. We also show that available data for the Hubble parameter as a function of redshift can be fitted using KCC and that this model does not suffer from any apparent age problem. Overall, KCC remains a viable alternative cosmological model, worthy of further investigation.
Halting Planet Migration in the Evacuated Centers of Protoplanetary Disks

Precise Doppler searches for extrasolar planets find a surfeit of planets with orbital periods of 3-4 days and no planets with orbital periods less than 3 days. The circumstellar distance R0, where small grains in a protoplanetary disk reach sublimation temperatures (~1500 K), corresponds to a period of ~6 days. Interior to R0, turbulent accretion due to magnetorotational instability may evacuate the disk center. We suggest that planets with orbital periods of 3-4 days are so common because migrating planets halt once this evacuated region contains the sites of their exterior 2 : 1 Lindblad resonances.
Proposal for a GHz count rate near-IR single-photon detector based on a nanoscale superconducting transition edge sensor

We describe a superconducting transition edge sensor based on a nanoscale niobium detector element. This device is predicted to be capable of energy-resolved near-IR single-photon detection with a GHz count rate. The increased speed and sensitivity of this device compared to traditional transition edge sensors result from the very small electronic heat capacity of the nanoscale detector element. In the present work, we calculate the predicted thermal response time and energy resolution. We also discuss approaches for achieving efficient optical coupling to the sub-wavelength detector element using a resonant near-IR antenna.
Time-Optimal Collaborative Guidance Using the Generalized Hopf Formula

Presented is a new method for calculating the time-optimal guidance control for a multiple vehicle pursuit-evasion system. A joint differential game of $k$ pursuing vehicles relative to the evader is constructed, and a Hamilton–Jacobi–Isaacs equation that describes the evolution of the value function is formulated. The value function is built such that the terminal cost is the squared distance from the boundary of the terminal surface. Additionally, all vehicles are assumed to have bounded controls. Typically, a joint state space constructed in this way would have too large a dimension to be solved with existing grid-based approaches. The value function is computed efficiently in high-dimensional space, without a discrete grid, using the generalized Hopf formula. The optimal time-to-reach is iteratively solved, and the optimal control is inferred from the gradient of the value function.
THREE-DIMENSIONAL SIMULATIONS OF PURE DEFLAGRATION MODELS FOR THERMONUCLEAR SUPERNOVAE

We present a systematic study of the pure deflagration model of Type Ia supernovae (SNe Ia) using three-dimensional, high-resolution, full-star hydrodynamical simulations, nucleosynthetic yields calculated using Lagrangian tracer particles, and light curves calculated using radiation transport. We evaluate the simulations by comparing their predicted light curves with many observed SNe Ia using the SALT2 data-driven model and find that the simulations may correspond to under-luminous SNe Iax. We explore the effects of the initial conditions on our results by varying the number of randomly selected ignition points from 63 to 3500, and the radius of the centered sphere they are confined in from 128 to 384 km. We find that the rate of nuclear burning depends on the number of ignition points at early times, the density of ignition points at intermediate times, and the radius of the confining sphere at late times. The results depend primarily on the number of ignition points, but we do not expect this to be the case in general. The simulations with few ignition points release more nuclear energy E{sub nuc}, have larger kinetic energies E{sub K}, and produce more {sup 56}Ni than those with many ignition points, and differ in the distribution ofmore » {sup 56}Ni, Si, and C/O in the ejecta. For these reasons, the simulations with few ignition points exhibit higher peak B-band absolute magnitudes M{sub B} and light curves that rise and decline more quickly; their M{sub B} and light curves resemble those of under-luminous SNe Iax, while those for simulations with many ignition points are not.« less
Structure identification methods for atomistic simulations of crystalline materials

We discuss existing and new computational analysis techniques to classify local atomic arrangements in large-scale atomistic computer simulations of crystalline solids. This article includes a performance comparison of typical analysis algorithms such as common neighbor analysis (CNA), centrosymmetry analysis, bond angle analysis, bond order analysis and Voronoi analysis. In addition we propose a simple extension to the CNA method that makes it suitable for multi-phase systems. Finally, we introduce a new structure identification algorithm, the neighbor distance analysis, which is designed to identify atomic structure units in grain boundaries.
COVID-19 Kaggle Literature Organization

The world has faced the devastating outbreak of Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2), or COVID-19, in 2020. Research in the subject matter was fast-tracked to such a point that scientists were struggling to keep up with new findings. With this increase in the scientific literature, there arose a need for organizing those documents. We describe an approach to organize and visualize the scientific literature on or related to COVID-19 using machine learning techniques so that papers on similar topics are grouped together. By doing so, the navigation of topics and related papers is simplified. We implemented this approach using the widely recognized CORD-19 dataset to present a publicly available proof of concept.
Room-temperature stability of excitons and transverse-electric polarized deep-ultraviolet luminescence in atomically thin GaN quantum wells

We apply first-principles calculations to study the effects of extreme quantum confinement on the electronic, excitonic, and radiative properties of atomically thin (1–4 atomic monolayers) GaN quantum wells embedded in AlN. We determine the quasiparticle bandgaps, exciton energies and wave functions, radiative lifetimes, and Mott critical densities as a function of well and barrier thickness. Our results show that quantum confinement in GaN monolayers increases the bandgap up to 5.44 eV and the exciton binding energy up to 215 meV, indicating the thermal stability of excitons at room temperature. Exciton radiative lifetimes range from 1 to 3 ns at room temperature, while the Mott critical density for exciton dissociation is approximately 1013 cm−2. The luminescence is transverse-electric polarized, which facilitates light extraction from c-plane heterostructures. We also introduce a simple approximate model for calculating the exciton radiative lifetime based on the free-carrier bimolecular radiative recombination coefficient and the exciton radius, which agrees well with our results obtained with the Bethe–Salpeter equation predictions. Our results demonstrate that atomically thin GaN quantum wells exhibit stable excitons at room temperature for potential applications in efficient light emitters in the deep ultraviolet as well as room-temperature excitonic devices.We apply first-principles calculations to study the effects of extreme quantum confinement on the electronic, excitonic, and radiative properties of atomically thin (1–4 atomic monolayers) GaN quantum wells embedded in AlN. We determine the quasiparticle bandgaps, exciton energies and wave functions, radiative lifetimes, and Mott critical densities as a function of well and barrier thickness. Our results show that quantum confinement in GaN monolayers increases the bandgap up to 5.44 eV and the exciton binding energy up to 215 meV, indicating the thermal stability of excitons at room temperature. Exciton radiative lifetimes range from 1 to 3 ns at room temperature, while the Mott critical density for exciton dissociation is approximately 1013 cm−2. The luminescence is transverse-electric polarized, which facilitates light extraction from c-plane heterostructures. We also introduce a simple approximate model for calculating the exciton radiative lifetime based on the free-carrier bimolecular radiative reco...