cssi/SciSciGPT-SciSciNet huggingface dataset:
An extension of cosmological dynamics with York time

It has been suggested that the York parameter T (effectively the scalar extrinsic curvature of a spatial hypersurface) may play the role of a fundamental time parameter. In a flat, forever expanding cosmology the York parameter remains always negative, taking values $$T=-\infty $$ at the big bang and approaching some finite non-positive value as $$t\rightarrow \infty $$ , t being the usual cosmological time coordinate. Based on previous results concerning a simple, spatially flat cosmological model with a scalar field, we provide a temporal extension of this model to include ‘times’ $$T>0$$ , an epoch not covered by the cosmological time coordinate t, and discuss the dynamics of this ‘other side’ and its significance. We argue that the extension is necessary if a consistent quantisation scheme is to exist. Furthermore, we investigate which types of potentials lead to smooth transitions, paying particular attention to currently favoured inflaton potentials.
Uniform Approximation of a Maxwellian Thermostat by Finite Reservoirs.

We study a system of M particles in contact with a large but finite reservoir of \({N \gg M}\) particles within the framework of the Kac master equation modeling random collisions. The reservoir is initially in equilibrium at temperature \({T=\beta^{-1}}\). We show that for large N, this evolution can be approximated by an effective equation in which the reservoir is described by a Maxwellian thermostat at temperature T. This approximation is proven for a suitable \({L^2}\) norm as well as for the Gabetta–Toscani–Wennberg (GTW) distance and is uniform in time.
A MACHINE LEARNING TECHNIQUE TO IDENTIFY TRANSIT SHAPED SIGNALS

We describe a new metric that uses machine learning to determine if a periodic signal found in a photometric time series appears to be shaped like the signature of a transiting exoplanet. This metric uses dimensionality reduction and k-nearest neighbors to determine whether a given signal is sufficiently similar to known transits in the same data set. This metric is being used by the Kepler Robovetter to determine which signals should be part of the Q1–Q17 DR24 catalog of planetary candidates. The Kepler Mission reports roughly 20,000 potential transiting signals with each run of its pipeline, yet only a few thousand appear to be sufficiently transit shaped to be part of the catalog. The other signals tend to be variable stars and instrumental noise. With this metric, we are able to remove more than 90% of the non-transiting signals while retaining more than 99% of the known planet candidates. When tested with injected transits, less than 1% are lost. This metric will enable the Kepler mission and future missions looking for transiting planets to rapidly and consistently find the best planetary candidates for follow-up and cataloging.
Brane boxes and branes on singularities

Brane Box Models of intersecting NS and D5 branes are mapped to D3 branes at 3/Γ singularities and viceversa, in a setup which gives rise to N = 1 supersymmetric gauge theories in four dimensions. The Brane Box Models are constructed on a two-torus. The map is interpreted as T-duality along the two directions of the torus. Some Brane Box Models contain NS fivebranes winding around (p,q) cycles in the torus, and our method provides the geometric T-dual to such objects. An amusing aspect of the mapping is that T-dual configurations are calculated using D = 4 N = 1 field theory data. The mapping to the singularity picture allows the geometrical interpretation of all the marginal couplings in finite field theories. This identification is further confirmed using the AdS/CFT correspondence for orbifold theories. The AdS massless fields coupling to the marginal operators in the boundary appear as stringy twisted sectors of S5/Γ. The mapping for theories which are non-finite requires the introduction of fractional D3 branes in the singularity picture.
High spatial frequency laser induced periodic surface structure formation in germanium by mid-IR femtosecond pulses

Formation of high spatial frequency laser induced periodic surface structures (HSFL) in germanium by 90 fs mid-IR pulses at a 1 kHz repetition rate with wavelengths between λ = 2 and 3.6 μm was studied with varying angle of incidence and polarization. The period of these structures varied from λ/3 to λ/8. A modified surface-scattering model including Drude excitation and the optical Kerr effect explains the spatial period scaling of HSFL across the mid-IR wavelengths. Transmission electron microscopy shows the presence of a 30 nm amorphous layer above the structure of crystalline germanium. Various mechanisms including two photon absorption and defect-induced amorphization are discussed as probable causes for the formation of this layer.
Find Unique Usages: Helping Developers Understand Common Usages

When working in large and complex codebases, developers face challenges using Find Usages to understand how to reuse classes and methods. To better understand these challenges, we conducted a small exploratory study with 4 participants. We found that developers often wasted time reading long lists of similar usages or prematurely focused on a single usage. Based on these findings, we hypothesized that clustering usages by the similarity of their surrounding context might enable developers to more rapidly understand how to use a function. To explore this idea, we designed and implemented Find Unique Usages, which extracts usages, computes a diff between pairs of usages, generates similarity scores, and uses these scores to form usage clusters. To evaluate this approach, we conducted a controlled experiment with 12 participants. We found that developers with Find Unique Usages were significantly faster, completing their task in 35% less time.
Stability of matter–antimatter molecules

Abstract We examine the stability of matter–antimatter molecules by reducing the four-body problem into a simpler two-body problem with residual interactions. We find that matter–antimatter molecules with constituents m 1 + , m 2 - , m ¯ 2 + , m ¯ 1 - possess bound states if their constituent mass ratio m1/m2 is greater than about 4. This stability condition suggests that the binding of matter–antimatter molecules is a rather common phenomenon. We evaluate the binding energies and eigenstates of matter–antimatter molecules μ + e - - e + μ - , π + e - - e + π - , K + e - - e + K - , ( pe - ) - e + p ¯ , ( p μ - ) - μ + p ¯ , and (K+μ−) − (μ+K−), which satisfy the stability condition. We estimate the molecular annihilation lifetimes in their s states.
A Circuit-Theoretic Approach to State Estimation

Traditional state estimation (SE) methods that are based on nonlinear minimization of the sum of localized measurement error functionals are known to suffer from non-convergence and large residual errors. In this paper we propose an equivalent circuit formulation (ECF)-based SE approach that inherently considers the complete network topology and associated physical constraints. We analyze the mathematical differences between the two approaches and show that our approach produces a linear state-estimator that is mathematically a quadratic programming (QP) problem with closed-form solution. Furthermore, this formulation imposes additional topology-based constraints that provably shrink the feasible region and promote convergence to a more physically meaningful solution. From a probabilistic viewpoint, we show that our method applies prior knowledge into the estimate, thus converging to a more physics-based estimate than the traditional observation-driven maximum likelihood estimator (MLE). Importantly, incorporation of the entire system topology and underlying physics, while being linear, makes ECF-based SE advantageous for large-scale systems.
Exploring Lattice Methods for Cold Fermionic Atoms

There has been a surge of experimental effort recently in cooling trapped fermionic atoms to quantum degeneracy. By varying an external magnetic field, interactions between atoms can be made arbitrarily strong. When the S wave scattering length becomes comparable to and larger than the interparticle spacing, standard mean field analysis breaks down. In this case the system exhibits a type of universality, and J-W. Chen and D.B. Kaplan [Phys. Rev. Lett. 92 (2004) 257002] recently showed how this system can be studied from first principles using lattice field theory. This poster presents the first results of exploratory simulations. The existence of a continuum limit is checked and the pairing condensate is studied as a function of the external source strength over a range of temperatures. Preliminary results show simulations can locate the critical temperature.
UNVEILING SU AURIGAE IN THE NEAR-INFRARED: NEW HIGH SPATIAL RESOLUTION RESULTS USING ADAPTIVE OPTICS

We present new results on the circumstellar nebulosity around SU Aurigae, a T Tauri star of about 2 M⊙ and 5 Myr old at 152 pc in the J, H, and K bands using high-resolution adaptive optics imaging (030) with the Penn State Near-IR Imager and Spectrograph at the 100 inch (2.5 m) Mount Wilson telescope. A comparison with Hubble Space Telescope STIS optical (0.2–1.1 μm) images shows that the orientation of the circumstellar nebulosity in the near-IR extends from position angle 210° to 270° in the H and K bands and up to 300° in the J band. We call the circumstellar nebulosity seen between 210° and 270° an "IR nebulosity." We find that the IR nebulosity (which extends up to 35 in the J band and 25 in the K band) is due to scattered light from the central star. The IR nebulosity is either a cavity formed by the stellar outflows or part of the circumstellar disk. We present a schematic three-dimensional geometric model of the disk and jet of SU Aur based on STIS and our near-IR observations. According to this model, the IR nebulosity is part of the circumstellar disk seen at high inclination angles. The extension of the IR nebulosity is consistent with estimates of the disk diameter of 50–400 AU in radius, from earlier millimeter K-band interferometric observations and SED fittings.
Superconducting Neuromorphic Computing Using Quantum Phase-Slip Junctions

Superconducting circuits based on quantum phase-slip junctions (QPSJs) can conduct quantized charge pulses, which naturally resemble action potentials generated by biological neurons. A corresponding synaptic circuit, which works as a weighted connection between two neurons, can also be realized by circuits comprised of QPSJs and magnetic Josephson junctions (MJJs) as a means of charge modulation for quantized charge propagation. In this paper, we present basic neuromorphic computing circuitry components, such as neuron and synaptic circuits, based on superconducting QPSJs and MJJs. Using a SPICE model developed for QPSJs, neuron and synaptic circuits were simulated in WRSPICE to demonstrate possible operation. We provide estimates for QPSJ energy dissipation and operation speed based on calculations using simple models. Some of the challenges for implementation of this technology are also briefly discussed.
A regularity result for the incompressible magnetohydrodynamics equations with free surface boundary

We consider the three-dimensional incompressible magnetohydrodynamics (MHD) equations in a bounded domain with small volume and free moving surface boundary. We establish a priori estimate for solutions with minimal regularity assumptions on the initial data in Lagrangian coordinates. In particular, due to the lack of the Cauchy invariance for MHD equations, the smallness assumption on the fluid domain is required to compensate a loss of control of the flow map. Moreover, we show that the magnetic field has certain regularizing effect which allows us to control the vorticity of the fluid and that of the magnetic field. To the best of our knowledge this is the first result that focuses on the low regularity solution for incompressible free-boundary MHD equations.
Sensitivity estimation for calculated phase equilibria

The development of a consistent framework for Calphad model sensitivity is necessary for the rational reduction of uncertainty via new models and experiments. In the present work, a sensitivity theory for Calphad was developed, and a closed‐form expression for the log‐likelihood gradient and Hessian of a multi‐phase equilibrium measurement was presented. The inherent locality of the defined sensitivity metric was mitigated through the use of Monte Carlo averaging. A case study of the Cr–Ni system was used to demonstrate visualizations and analyses enabled by the developed theory. Criteria based on the classical Cramer–Rao bound were shown to be a useful diagnostic in assessing the accuracy of parameter covariance estimates from Markov Chain Monte Carlo. The developed sensitivity framework was applied to estimate the statistical value of phase equilibria measurements in comparison with thermochemical measurements, with implications for Calphad model uncertainty reduction.
High-performance nanoscale topological energy transduction.

The realization of high-performance, small-footprint, on-chip inductors remains a challenge in radio-frequency and power microelectronics, where they perform vital energy transduction in filters and power converters. Modern planar inductors consist of metallic spirals that consume significant chip area, resulting in low inductance densities. We present a novel method for magnetic energy transduction that utilizes ferromagnetic islands (FIs) on the surface of a 3D time-reversal-invariant topological insulator (TI) to produce paradigmatically different inductors. Depending on the chemical potential, the FIs induce either an anomalous or quantum anomalous Hall effect in the topological surface states. These Hall effects direct current around the FIs, concentrating magnetic flux and producing a highly inductive device. Using a novel self-consistent simulation that couples AC non-equilibrium Green functions to fully electrodynamic solutions of Maxwell’s equations, we demonstrate excellent inductance densities up to terahertz frequencies, thus harnessing the unique properties of topological materials for practical device applications.
Minimal Models for Nonreciprocal Amplification Using Biharmonic Drives

Detection and efficient readout of weak signals in the quantum regime are critical aspects of quantum information processing. Current measurement protocols rely on amplifiers plus signal routers (circulators or isolators), but bulk is problematic for any scalable architecture. The authors present minimal, efficient schemes to design nonreciprocal quantum-limited amplifiers for simultaneous routing and boosting of signals. This could lead to significantly simpler measurement chains, which is especially relevant in the face of increasingly complex multi-qubit experiments.
Adverse Childhood Experiences Ontology for Mental Health Surveillance, Research, and Evaluation: Advanced Knowledge Representation and Semantic Web Techniques.

Background: Adverse Childhood Experiences (ACEs), a set of negative events and processes that a person might encounter during childhood and adolescence, have been proven to be linked to increased risks of a multitude of negative health outcomes and conditions when children reach adulthood and beyond. Objective: To better understand the relationship between ACEs and their relevant risk factors with associated health outcomes and to eventually design and implement preventive interventions, access to an integrated coherent dataset is needed. Therefore, we implemented a formal ontology as a resource to allow the mental health community to facilitate data integration and knowledge modeling and to improve ACEs’ surveillance and research. Methods: We use advanced knowledge representation and semantic Web tools and techniques to implement the ontology. The current implementation of the ontology is expressed in the description logic ALCRIQ(D), a sublogic of Web Ontology Language (OWL 2). Results: The ACEs Ontology has been implemented and made available to the mental health community and the public via the BioPortal repository. Moreover, multiple use-case scenarios have been introduced to showcase and evaluate the usability of the ontology in action. The ontology was created to be used by major actors in the ACEs community with different applications, from the diagnosis of individuals and predicting potential negative outcomes that they might encounter to the prevention of ACEs in a population and designing interventions and policies. Conclusions: The ACEs Ontology provides a uniform and reusable semantic network and an integrated knowledge structure for mental health practitioners and researchers to improve ACEs’ surveillance and evaluation.
Atmospheric Circulation, Chemistry, and Infrared Spectra of Titan-like Exoplanets around Different Stellar Types

With the discovery of ever smaller and colder exoplanets, terrestrial worlds with hazy atmospheres must be increasingly considered. Our Solar System's Titan is a prototypical hazy planet, whose atmosphere may be representative of a large number of planets in our Galaxy. As a step towards characterizing such worlds, we present simulations of exoplanets that resemble Titan, but orbit three different stellar hosts: G-, K-, and M-dwarf stars. We use general circulation and photochemistry models to explore the circulation and chemistry of these Titan-like planets under varying stellar spectra, in all cases assuming a Titan-like insolation. Due to the strong absorption of visible light by atmospheric haze, the redder radiation accompanying later stellar types produces more isothermal stratospheres, stronger meridional temperature gradients at mbar pressures, and deeper and stronger zonal winds. In all cases, the planets' atmospheres are strongly superrotating, but meridional circulation cells are weaker aloft under redder starlight. The photochemistry of hydrocarbon and nitrile species varies with stellar spectra, with variations in the FUV/NUV flux ratio playing an important role. Our results tentatively suggest that column haze production rates could be similar under all three hosts, implying that planets around many different stars could have similar characteristics to Titan's atmosphere. Lastly, we present theoretical emission spectra. Overall, our study indicates that, despite important and subtle differences, the circulation and chemistry of Titan-like exoplanets are relatively insensitive to differences in host star. These findings may be further probed with future space-based facilities, like WFIRST, LUVOIR, HabEx, and OST.
Disassociation energies for the finite-density N-body problem

This paper considers the energy required for collections of finite-density bodies to undergo escape under internal gravitational interactions alone. As the level of the system energy is increased, there are different combinations of components that can escape, until the total energy becomes positive, when the entire system can undergo mutual disruption. The results are also defined for bodies modeled as a continuum. These results provide rigorous constraints for the disruption of rubble-pile asteroids when only considering gravitational interaction effects, with the energy provided by rotation of an initial collection of the system. These issues are considered for discrete particles in the N-body problem and for size distributions of discrete particles in the continuum limit.
Magnetism and the Invisible Man: The mysteries of coronal cavities

Magnetism defines the complex and dynamic solar corona. Twists and tangles in coronal magnetic fields build up energy and ultimately erupt, hurling plasma into interplanetary space. These coronal mass ejections (CMEs) are transient riders on the ever-outflowing solar wind, which itself possesses a three-dimensional morphology shaped by the global coronal magnetic field. Coronal magnetism is thus at the heart of any understanding of the origins of space weather at the Earth. However, we have historically been limited by the difficulty of directly measuring the magnetic fields of the corona, and have turned to observations of coronal plasma to trace out magnetic structure. This approach is complicated by the fact that plasma temperatures and densities vary among coronal magnetic structures, so that looking at any one wavelength of light only shows part of the picture. In fact, in some regimes it is the lack of plasma that is a significant indicator of the magnetic field. Such a case is the coronal cavity: a dark, elliptical region in which strong and twisted magnetism dwells. I will elucidate these enigmatic features by presenting observations of coronal cavities in multiple wavelengths and from a variety of observing vantages, including unprecedented coronal magnetic field measurements now being obtained by the Coronal Multichannel Polarimeter (CoMP). These observations demonstrate the presence of twisted magnetic fields within cavities, and also provide clues to how and why cavities ultimately erupt as CMEs.
Well-posedness and derivative blow-up for a dispersionless regularized shallow water system

We study local-time well-posedness and breakdown for solutions of regularized Saint-Venant equations (regularized classical shallow water equations) recently introduced by Clamond and Dutykh. The system is linearly non-dispersive, and smooth solutions conserve an H 1-equivalent energy. No shock discontinuities can occur, but the system is known to admit weakly singular shock-profile solutions that dissipate energy. We identify a class of small-energy smooth solutions that develop singularities in the first derivatives in finite time.
An $L^p$ theory of sparse graph convergence I: limits, sparse random graph models, and power law distributions

We introduce and develop a theory of limits for sequences of sparse graphs based on Lp graphons, which generalizes both the existing L1 theory of dense graph limits and its extension by Bollobas and Riordan to sparse graphs without dense spots. In doing so, we replace the no dense spots hypothesis with weaker assumptions, which allow us to analyze graphs with power law degree distributions. This gives the rst broadly applicable limit theory for sparse graphs with unbounded average degrees. In this paper, we lay the foundations of the Lp theory of graphons, characterize convergence, and develop corresponding random graph models, while we prove the equivalence of several alternative metrics in a companion paper.
Continuous image distortion by astrophysical thick lenses

Image distortion due to weak gravitational lensing is examined using a non-perturbative method of integrating the geodesic deviation and optical scalar equations along the null geodesics connecting the observer to a distant source. The method we develop continuously changes the shape of the pencil of rays from the source to the observer with no reference to lens planes in astrophysically relevant scenarios. We compare the projected area and the ratio of semi-major to semi-minor axes of the observed elliptical image shape for circular sources from the continuous, thick-lens method with the commonly assumed thin-lens approximation. We find that for truncated singular isothermal sphere and NFW models of realistic galaxy clusters, the commonly used thin-lens approximation is accurate to better than 1 part in 104 in predicting the image area and axes ratios. For asymmetric thick lenses consisting of two massive clusters separated along the line of sight in redshift up to Δz = 0.2, we find that modeling the image distortion as two clusters in a single lens plane does not produce relative errors in image area or axes ratio more than 0.5%.
Diffusion in a rough potential: Dual-scale structure and regime crossovers.

Diffusion in a “rough” potential parameterized by a reaction coordinate q is relevant to a wide spectrum of problems ranging from protein folding and charge transport in complex media to colloidal stabilization and self-assembly. This work studies the case of a potential having a coarse-scale structure with characteristic energy barrier ΔU and period l and fine-scale “roughness” of magnitude ΔU′ ≲ ΔU and small period l′ ≪ l. The numerical solution of the Smoluchowski equation and analytical predictions from Kramers theory document distinct regimes at different distances |Δq| = |q − qE| from stable equilibrium at q = qE. The physical diffusivity D prescribed by dissipative effects can be observed farther than a distance |Δq′| ∝ (ΔU′/l′ + ΔU/l). Rescaling the physical diffusivity to account for the fine-scale “roughness” is strictly valid when |Δq| |Δq| > ΔqIII and exponential decay over time for |Δq| < ΔqIII ∝ 1/l. The effective diffusivity derived in this work is sensitive to the coarse- and fine-scale energy barriers and periods and for l′/l → 0 and ΔU′/kBT ≫ 1 agrees closely with mean first-passage time estimates currently employed, which depend solely on the fine-scale energy barrier.Diffusion in a “rough” potential parameterized by a reaction coordinate q is relevant to a wide spectrum of problems ranging from protein folding and charge transport in complex media to colloidal stabilization and self-assembly. This work studies the case of a potential having a coarse-scale structure with characteristic energy barrier ΔU and period l and fine-scale “roughness” of magnitude ΔU′ ≲ ΔU and small period l′ ≪ l. The numerical solution of the Smoluchowski equation and analytical predictions from Kramers theory document distinct regimes at different distances |Δq| = |q − qE| from stable equilibrium at q = qE. The physical diffusivity D prescribed by dissipative effects can be observed farther than a distance |Δq′| ∝ (ΔU′/l′ + ΔU/l). Rescaling the physical diffusivity to account for the fine-scale “roughness” is strictly valid when |Δq| < ΔqI ∝ (ΔU′/l′ − ΔU/l). Farther than a critical distance ΔqII ∝ ΔU/l, the diffusion process is free of coarse-scale metastable states, which facilitates determi...
On the Bateman-Horn conjecture for polynomials over large finite fields

We prove an analogue of the classical Bateman–Horn conjecture on prime values of polynomials for the ring of polynomials over a large finite field. Namely, given non-associate, irreducible, separable and monic (in the variable ) polynomials , we show that the number of of degree such that all , are irreducible is where is the generic degree of for and is the number of factors into which splits over . Our proof relies on the classification of finite simple groups. We will also prove the same result for non-associate, irreducible and separable (over ) polynomials not necessarily monic in under the assumptions that is greater than the number of geometric points of multiplicity greater than two on the (possibly reducible) affine plane curve defined by the equation (this number is always bounded above by , where denotes the total degree in ) and where is the generic degree of for .
The gap of Fredkin quantum spin chain is polynomially small

We prove a new result on the spectral gap and mixing time of a Markov chain with Glauber dynamics on the space of Dyck paths (i.e., Catalan paths) and their generalization, which we call colored Dyck paths. The proof uses the comparison theorem of Diaconis and Saloff-Coste and our previous results. Let $2n$ be the number of spins. We prove that the gap of the Fredkin quantum spin chain Hamiltonian [6, 20], is $\Theta(n^{-c})$ with $c\ge2$. Our results on the spectral gap of the Markov chain are used to prove a lower bound of $O(n^{-15/2})$ on the energy of first excited state above the ground state of the Fredkin quantum spin chain. We prove an upper bound of $O(n^{-2})$ using the universality of Brownian motion and convergence of Dyck random walks to Brownian excursions. Lastly, the 'unbalanced' ground state energies are proved to be polynomially small in $n$ by mapping the Hamiltonian to an effective hopping Hamiltonian with next nearest neighbor interactions and analytically solving its ground state.
The evaluation of non-topological components in Berry phase and momentum relaxation time in a gapped 3D topological insulator

The zero gap surface states of a 3D-topological insulator host Dirac fermions with spin locked to the momentum. The gap-less Dirac fermions exhibit electronic behaviour different from those predicted in conventional materials. While calculations based on a simple linear dispersion can account for observed experimental patterns, a more accurate description of the physics of these systems and a better agreement between experimental data theoretical results can be obtained by including higher order terms in the Hamiltonian. In this work, in presence of a time reversal symmetry breaking external magnetic field and higher order warping term, alteration to the topologically ordained Berry phase of , momentum relaxation time, and the magneto-conductivity tensors is established. The relation between scattering times and the deviations to topological Berry phase of is also emphasized.
Correlated Frequency-Changes of Trapped Vertical p-mode Oscillations and kHz QPOs

AbstractWe have examined the frequencies of trapped two-armed (m = 2) nearly verticaloscillations (vertical p-mode) in vertically isothermal disks with toroidal magneticﬁelds. The magnetic ﬁelds are stratiﬁed so that the Alfv´en speed, c A , is constant inthe vertical direction. We have particularly focused our attention on how frequenciesof the fundamental mode (n r = 0) and ﬁrst overtone (n r = 1) in the radial directionchange with correlation, when theratioc 2A /cs changes, c s beingthe isothermal acousticspeed. The results show that in the case where the oscillations are fundamentalmode (n=1) in the vertical direction, the correlated frequency changes of the above-mentioned oscillations seem towell describe, withstandard values ofthe mass andspinof the central sources, the frequency correlation of kHz QPOs observed in neutron-starX-ray binaries.Key words:accretion, accrection disks — quasi-periodic oscillations — verticalp-mode oscillations — waves — X-rays; stars1. IntroductionMany authors now think that the kilo-hertz quasi-periodic oscillations (kHz QPOs) ob-served in low-mass X-ray binaries (LMXBs) are some kinds of disk oscillations in a strong gravi-tational ﬁeld. Understanding their origin is of importance, since it will become a promising toolto evaluate the mass and spin of the central sources as well as the disk structure surrounding thesources. Many models of kHz QPOs related to disk oscillations and waves have been proposed.None of them, however, can suﬃciently well describe the observed frequency correlation of thetwin kHz QPOs (Lin et al. 2010).As one of possible models of kHz QPOs, for example, we proposed a disk-oscillationmodel in deformed disks (Kato and Fukue 2006), based on the fact that in deformed disks aset of oscillations with positive and negative wave energies are excited resonantly (Kato 2004,1
Physical versus mathematical billiards: From regular dynamics to chaos and back

In standard (mathematical) billiards, a point particle moves uniformly in a billiard table with elastic reflections off the boundary. We show that in transition from mathematical billiards to physical billiards, where a finite-size hard sphere moves at the same billiard table, virtually anything may happen. Namely, a nonchaotic billiard may become chaotic and vice versa. Moreover, both these transitions may occur softly, i.e., for any (arbitrarily small) positive value of the radius of a physical particle, as well as by a “hard” transition when radius of the physical particle must exceed some critical strictly positive value. Such transitions may change a phase portrait of a mathematical billiard locally as well as globally. These results are somewhat unexpected because for standard examples of billiards, their dynamics remains absolutely the same after replacing a point particle by a finite-size (“physical”) particle. Moreover, we show that a character of dynamics may change several times when the size of particle is increasing.
The matching polytope does not admit fully-polynomial size relaxation schemes

The groundbreaking work of Rothvos [2014] established that every linear program expressing the matching polytope has an exponential number of inequalities (formally the matching polytope has exponential extension complexity). We generalize this result by deriving strong bounds on the polyhedral inapproximability of the matching polytope: for fixed 0
Hamiltonian mechanics is conservation of information entropy

Abstract In this work we show the equivalence between Hamiltonian mechanics and conservation of information entropy. We will show that distributions with coordinate independent values for information entropy require that the manifold on which the distribution is defined is charted by conjugate pairs (i.e. it is a symplectic manifold). We will also show that further requiring that the information entropy is conserved during the evolution yields Hamilton's equations.
Kronecker PCA based spatio-temporal modeling of video for dismount classification

We consider the application of KronPCA spatio-temporal modeling techniques 1, 2 to the extraction of spatiotemporal features for video dismount classification. KronPCA performs a low-rank type of dimensionality reduction that is adapted to spatio-temporal data and is characterized by the T frame multiframe mean μ and covariance ∑ of p spatial features. For further regularization and improved inverse estimation, we also use the diagonally corrected KronPCA shrinkage methods we presented in. 1 We apply this very general method to the modeling of the multivariate temporal behavior of HOG features extracted from pedestrian bounding boxes in video, with gender classification in a challenging dataset chosen as a specific application. The learned covariances for each class are used to extract spatiotemporal features which are then classified, achieving competitive classification performance.
THE DISTRIBUTION OF ALPHA ELEMENTS IN ULTRA-FAINT DWARF GALAXIES

The Milky Way ultra-faint dwarf (UFD) galaxies contain some of the oldest, most metal-poor stars in the universe. We present [Mg/Fe], [Si/Fe], [Ca/Fe], [Ti/Fe], and mean [α/Fe] abundance ratios for 61 individual red giant branch stars across eight UFDs. This is the largest sample of alpha abundances published to date in galaxies with absolute magnitudes MV > –8, including the first measurements for Segue 1, Canes Venatici II, Ursa Major I, and Leo T. Abundances were determined via medium-resolution Keck/DEIMOS spectroscopy and spectral synthesis. The sample spans the metallicity range –3.4 <[Fe/H] < –1.1. With the possible exception of Segue 1 and Ursa Major II, the individual UFDs show on average lower [α/Fe] at higher metallicities, consistent with enrichment from Type Ia supernovae. Thus, even the faintest galaxies have undergone at least a limited level of chemical self-enrichment. Together with recent photometric studies, this suggests that star formation in the UFDs was not a single burst, but instead lasted at least as much as the minimum time delay of the onset of Type Ia supernovae (~100 Myr) and less than ~2 Gyr. We further show that the combined population of UFDs has an [α/Fe] abundance pattern that is inconsistent with a flat, Galactic halo-like alpha abundance trend, and is also qualitatively different from that of the more luminous CVn I dSph, which does show a hint of a plateau at very low [Fe/H].
Hyperledger fabric: a distributed operating system for permissioned blockchains

Fabric is a modular and extensible open-source system for deploying and operating permissioned blockchains and one of the Hyperledger projects hosted by the Linux Foundation (www.hyperledger.org). Fabric is the first truly extensible blockchain system for running distributed applications. It supports modular consensus protocols, which allows the system to be tailored to particular use cases and trust models. Fabric is also the first blockchain system that runs distributed applications written in standard, general-purpose programming languages, without systemic dependency on a native cryptocurrency. This stands in sharp contrast to existing block-chain platforms that require "smart-contracts" to be written in domain-specific languages or rely on a cryptocurrency. Fabric realizes the permissioned model using a portable notion of membership, which may be integrated with industry-standard identity management. To support such flexibility, Fabric introduces an entirely novel blockchain design and revamps the way blockchains cope with non-determinism, resource exhaustion, and performance attacks. This paper describes Fabric, its architecture, the rationale behind various design decisions, its most prominent implementation aspects, as well as its distributed application programming model. We further evaluate Fabric by implementing and benchmarking a Bitcoin-inspired digital currency. We show that Fabric achieves end-to-end throughput of more than 3500 transactions per second in certain popular deployment configurations, with sub-second latency, scaling well to over 100 peers.
Self-Supervised Knowledge Triplet Learning for Zero-Shot Question Answering

The aim of all Question Answering (QA) systems is to generalize to unseen questions. Current supervised methods are reliant on expensive data annotation. Moreover, such annotations can introduce unintended annotator bias, making systems focus more on the bias than the actual task. This work proposes Knowledge Triplet Learning (KTL), a self-supervised task over knowledge graphs. We propose heuristics to create synthetic graphs for commonsense and scientific knowledge. We propose using KTL to perform zero-shot question answering, and our experiments show considerable improvements over large pre-trained transformer language models.
Poincaré duality and periodicity

We construct periodic families of Poincare complexes, partially solving a question of Hodgson that was posed in the proceedings of the 1982 Northwestern homotopy theory conference. We also construct infinite families of Poincare complexes whose top cell falls off after one suspension but which fail to embed in a sphere of codimension one. We give a homotopy theoretic description of the four-fold periodicity in knot cobordism.
Quantum Supergroups III. Twistors

We establish direct connections at several levels between quantum groups and supergroups associated to bar-consistent anisotropic super Cartan datum by constructing an automorphism (called twistor) in the setting of covering quantum groups. The canonical bases of the halves of quantum groups and supergroups are shown to match under the twistor up to powers of \({\sqrt{-1}}\). We further show that the modified quantum group and supergroup are isomorphic over the rational function field adjoined with \({\sqrt{-1}}\), by constructing a twistor on the modified covering quantum group. An equivalence of categories of weight modules for quantum groups and supergroups follows. Le plus court chemin entre deux verites dans le domaine reel passe par le domaine complexe. —Jacques Hadamard
The perfect local Tb Theorem and twisted Martingale transforms

A local Tb Theorem provides a flexible framework for proving the boundedness of a Calder\'on-Zygmund operator T. One needs only boundedness of the operator T on systems of locally pseudo-accretive functions \{b_Q\}, indexed by cubes. We give a new proof of this Theorem in the setting of perfect (dyadic) models of Calder\'on-Zygmund operators, imposing integrability conditions on the b_Q functions that are the weakest possible. The proof is a simple direct argument, based upon a new inequality for transforms of so-called twisted martingale differences.
Motion-Based Object Segmentation Based on Dense RGB-D Scene Flow

Given two consecutive RGB-D images, we propose a model that estimates a dense three-dimensional (3D) motion field, also known as scene flow . We take advantage of the fact that in robot manipulation scenarios, scenes often consist of a set of rigidly moving objects. Our model jointly estimates the following: First, the segmentation of the scene into an unknown but finite number of objects, second, the motion trajectories of these objects, and finally, the object scene flow. We employ an hourglass, deep neural network architecture. In the encoding stage, the RGB and depth images undergo spatial compression and correlation. In the decoding stage, the model outputs three images containing a per-pixel estimate of the corresponding object center as well as object translation and rotation. This forms the basis for inferring the object segmentation and final object scene flow. To evaluate our model, we generated a new and challenging, large scale, synthetic dataset that is specifically targeted at robotic manipulation: It contains a large number of scenes with a very diverse set of simultaneously moving 3D objects and is recorded with a simulated, static RGB-D camera. In quantitative experiments, we show that we outperform state-of-the-art scene flow and motion-segmentation methods on this data set. In qualitative experiments, we show how our learned model transfers to challenging real-world scenes, visually generating better results than existing methods.
Horizon-preserving dualities and perturbations in non-canonical scalar field cosmologies

We generalize the cosmological duality between inflation and cyclic contraction under the interchange a↔H to the case of non-canonical scalar field theories with varying speed of sound. The single duality in the canonical case generalizes to a family of three dualities constructed to leave the cosmological acoustic horizon invariant. We find three classes of models: (I) DBI inflation, (II) the non-canonical generalization of cyclic contraction, and (III) a new cosmological solution with rapidly decreasing speed of sound and relatively slowly growing scale factor, which we dub stalled cosmology. We construct dual analogs to the inflationary slow roll approximation, and solve for the curvature perturbation in all three cases. Both cyclic contraction and stalled cosmology predict a strongly blue spectrum for the curvature perturbations inconsistent with observations.
Design rules for the self-assembly of a protein crystal

Theories of protein crystallization based on spheres that form close-packed crystals predict optimal assembly within a ‘slot’ of second virial coefficients and enhanced assembly near the metastable liquid–vapor critical point. However, most protein crystals are open structures stabilized by anisotropic interactions. Here, we use theory and simulation to show that assembly of one such structure is not predicted by the second virial coefficient or enhanced by the critical point. Instead, good assembly requires that the thermodynamic driving force be on the order of the thermal energy and that interactions be made as nonspecific as possible without promoting liquid–vapor phase separation.
Implications of new CMB data for neutralino dark matter

Abstract The combination of new cosmic microwave background data with cosmological priors has determined the physical cold dark matter (cdm) density to be Ω cdm h 2 =0.13±0.01 . We find the corresponding regions of parameters in the minimal supergravity model for which the lightest neutralino is the cdm particle. We then compare with the muon anomalous magnetic moment ( a μ ) measurement, the mass of the lighter CP-even Higgs boson ( h 0 ), the trilepton search at the upgraded Fermilab Tevatron collider, and a direct search for relic neutralinos. The intersection of Ω cdm h 2 and a μ constraints selects tan β ≈40–45.
Deflating Super-puffs: Impact of Photochemical Hazes on the Observed Mass–Radius Relationship of Low-mass Planets

The observed mass-radius relationship of low-mass planets informs our understanding of their composition and evolution. Recent discoveries of low mass, large radii objects ("super-puffs") have challenged theories of planet formation and atmospheric loss, as their high inferred gas masses make them vulnerable to runaway accretion and hydrodynamic escape. Here we propose that high altitude photochemical hazes could enhance the observed radii of low-mass planets and explain the nature of super-puffs. We construct model atmospheres in radiative-convective equilibrium and compute rates of atmospheric escape and haze distributions, taking into account haze coagulation, sedimentation, diffusion, and advection by an outflow wind. We develop mass-radius diagrams that include atmospheric lifetimes and haze opacity, which is enhanced by the outflow, such that young (~0.1-1 Gyr), warm (T$_{eq}$ $\geq$ 500 K), low mass objects ($M_c$ < 4M$_{\rm Earth}$) should experience the most apparent radius enhancement due to hazes, reaching factors of three. This reconciles the densities and ages of the most extreme super-puffs. For Kepler-51b, the inclusion of hazes reduces its inferred gas mass fraction to <10%, similar to that of planets on the large radius side of the sub-Neptune radius gap. This suggests that Kepler-51b may be evolving towards that population, and that some warm sub-Neptunes may have evolved from super-puffs. Hazes also render transmission spectra of super-puffs and sub-Neptunes featureless, consistent with recent measurements. Our hypothesis can be tested by future observations of super-puffs' transmission spectra at mid-infrared wavelengths, where we predict that the planet radius will be half of that observed in the near-infrared.
Simplified vehicle–bridge interaction for medium to long-span bridges subject to random traffic load

This study introduces a simplified model for bridge–vehicle interaction for medium- to long-span bridges subject to random traffic loads. Previous studies have focused on calculating the exact response of the vehicle or the bridge based on an interaction force derived from the compatibility between two systems. This process requires multiple iterations per time step per vehicle until the compatibility is reached. When a network of vehicles is considered, the compatibility equation turns to a system of coupled equations which dramatically increases the complexity of the convergence process. In this study, we simplify the problem into two sub-problems that are decoupled: (a) a bridge subject to random excitation, and (b) individual sensing agents that are subjected to linear superposition of the bridge response and the road profile roughness. The study provides sufficient evidences to confirm that the proposed simulation approach is valid with minimal error when the bridge span is medium to long, and the spatio-temporal load pattern can be modeled as random white noise. The latter assumption is verified using a comparative study on a random traffic network. Quantitatively, the proposed approach is over 1000 times computationally more efficient when compared to the conventional approach for a 500 m long bridge, with response simulation errors below 0.1%.
Dihedral manifold approximate fibrations over the circle

Consider the cyclic group C2 of order two acting by complex-conjugation on the unit circle S1. The main result is that a finitely dominated manifold W of dimension > 4 admits a cocompact, free, discontinuous action by the infinite dihedral group D∞ if and only if W is the infinite cyclic cover of a free C2-manifold M such that M admits a C2-equivariant manifold approximate fibration to S1. The novelty in this setting is the existence of codimension-one, invariant submanifolds of M and W. Along the way, we develop an equivariant sucking principle for orthogonal actions of finite groups on Euclidean space.
Logarithmic operators and logarithmic conformal field theories

Logarithmic operators and logarithmic conformal field theories are reviewed. Prominent examples considered here include c = ?2 and c = 0 logarithmic conformal field theories. c = 0 logarithmic conformal field theories are especially interesting since they describe some of the critical points of a variety of longstanding problems involving a two dimensional quantum particle moving in a spatially random potential, as well as critical two dimensional self-avoiding random walks and percolation. Lack of classification of logarithmic conformal field theories remains a major impediment to progress towards finding complete solutions to these problems.