cssi/SciSciGPT-SciSciNet huggingface dataset:
A New Channel for the Detection of Planetary Systems through Microlensing. I. Isolated Events due to Planet Lenses

We propose and evaluate the feasibility of a new strategy to search for planets via microlensing observations. This new strategy is designed to detect planets in "wide" orbits, i.e., with orbital separation, a, greater than ~1.5RE. Planets in wide orbits may provide the dominant channel for the discovery of planets via microlensing, particularly low-mass (e.g., Earth-mass) planets. This paper concentrates on events in which a single planet serves as a lens, leading to an isolated event of short duration. We point out that a distribution of events due to lensing by stars with wide-orbit planets is necessarily accompanied by a distribution of shorter duration events. The fraction of events in the latter distribution is proportional to the average value of q1/2, where q is the ratio between planet and stellar masses. The position of the peak or peaks also provides a measure of the mass ratios typical of planetary systems. We study detection strategies that can optimize our ability to discover isolated short-duration events due to lensing by planets and find that monitoring employing sensitive photometry is particularly useful. If planetary systems similar to our own are common, even modest changes in detection strategy should lead to the discovery a few isolated events of short duration every year. We therefore also address the issue of the contamination due to stellar populations of any microlensing signal due to low-mass MACHOs. We describe how, even for isolated events of short duration, it will be possible to test the hypothesis that the lens was a planet instead of a low-mass MACHO, if the central star of the planetary system contributes a measurable fraction of the baseline flux.
Simulation with Fluctuating and Singular Rates

In this paper we present a method to generate independent samples for a general random variable, either continuous or discrete. The algorithm is an extension of the Acceptance-Rejection method, and it is particularly useful for kinetic simulation in which the rates are fluctuating in time and have singular limits, as occurs for example in simulation of recombination interactions in a plasma. Although it depends on some additional requirements, the new method is easy to implement and rejects less samples than the Acceptance-Rejection method.
Scaling and Balancing for High-Performance Computation of Optimal Controls

It is well known that proper scaling can increase the efficiency of computational problems. In this paper, we define and show that a balancing technique can substantially improve the computational ...
The isoperimetric problem in Riemannian optical geometry

In general relativity, spatial light rays of static spherically symmetric spacetimes are geodesics of surfaces in Riemannian optical geometry. In this paper, we apply results on the isoperimetric problem to show that length-minimizing curves subject to an area constraint are circles, and discuss implications for the photon spheres of Schwarzschild, Reissner-Nordstrom, as well as continuous mass models solving the Tolman-Oppenheimer-Volkoff equation. Moreover, we derive an isoperimetric inequality for gravitational lensing in Riemannian optical geometry, using curve shortening flow and the Gauss-Bonnet theorem.
Asymptotic structure in substitution tiling spaces

Every sufficiently regular non-periodic space of tilings of $\mathbb {R}^d$ has at least one pair of distinct tilings that are asymptotic under translation in all the directions of some open $(d-1)$ -dimensional hemisphere. If the tiling space comes from a substitution, there is a way of defining a location on such tilings at which asymptoticity ‘starts’. This leads to the definition of the branch locus of the tiling space: this is a subspace of the tiling space, of dimension at most $d-1$ , that summarizes the ‘asymptotic in at least a half-space’ behavior in the tiling space. We prove that if a $d$ -dimensional self-similar substitution tiling space has a pair of distinct tilings that are asymptotic in a set of directions that contains a closed $(d-1)$ -hemisphere in its interior, then the branch locus is a topological invariant of the tiling space. If the tiling space is a two-dimensional self-similar Pisot substitution tiling space, the branch locus has a description as an inverse limit of an expanding Markov map on a zero- or one-dimensional simplicial complex.
Asymmetric Magnetic Reconnection in Weakly Ionized Chromospheric Plasmas

Realistic models of magnetic reconnection in the solar chromosphere must take into account that the plasma is partially ionized and that plasma conditions within any two magnetic flux bundles undergoing reconnection may not be the same. Asymmetric reconnection in the chromosphere may occur when newly emerged flux interacts with pre-existing, overlying flux. We present 2.5D simulations of asymmetric reconnection in weakly ionized, reacting plasmas where the magnetic field strengths, ion and neutral densities, and temperatures are different in each upstream region. The plasma and neutral components are evolved separately to allow non-equilibrium ionization. As in previous simulations of chromospheric reconnection, the current sheet thins to the scale of the neutral?ion mean free path and the ion and neutral outflows are strongly coupled. However, the ion and neutral inflows are asymmetrically decoupled. In cases with magnetic asymmetry, a net flow of neutrals through the current sheet from the weak-field (high-density) upstream region into the strong-field upstream region results from a neutral pressure gradient. Consequently, neutrals dragged along with the outflow are more likely to originate from the weak-field region. The Hall effect leads to the development of a characteristic quadrupole magnetic field modified by asymmetry, but the X-point geometry expected during Hall reconnection does not occur. All simulations show the development of plasmoids after an initial laminar phase.
Elastic Microplane Formulation for Transversely Isotropic Materials

This contribution investigates the extension of the microplane formulation to the description of transversely isotropic materials such as shale rock, foams, unidirectional composites, and ceramics. Two possible approaches are considered: 1) the spectral decomposition of the stiffness tensor to define the microplane constitutive laws in terms of energetically orthogonal eigenstrains and eigenstresses; and 2) the definition of orientation-dependent microplane elastic moduli. It is shown that the first approach provides a rigorous way to tackle anisotropy within the microplane framework whereas the second approach represents an approximation which, however, makes the formulation of nonlinear constitutive equations much simpler. The efficacy of the second approach in modeling the macroscopic elastic behavior is compared to the thermodynamic restrictions of the anisotropic parameters showing that a significant range of elastic properties can be modeled with excellent accuracy. Further, it is shown that it provides a very good approximation of the microplane stresses provided by the first approach, with the advantage of a simpler formulation. It is concluded that the spectral stiffness decomposition represents the best approach in such cases as for modeling unidirectional composites, in which accurately capturing the elastic behavior is important. The introduction of orientation-dependent microplane elastic moduli provides a simpler framework for the modeling of transversely isotropic materials with remarked inelastic behavior, as in the case, for example, of shale rock.
Wireless Video Multicast With Cooperative and Incremental Transmission of Parity Packets

This paper introduces a novel and efficient approach for user cooperation in wireless video multicast using randomized distributed space time codes (R-DSTC), in which the sender first transmits the source packets, and the sender and receivers that have received all source packets then generate and send the parity packets simultaneously using R-DSTC. As more parity packets are delivered, more receivers can recover all source packets and join the parity packet transmission. Four variations of the proposed systems are considered. The first one requires complete channel information between the sender and all receivers and between all receivers to derive the optimal transmission rates for sending source and parity packets, and employs receiver feedback to determine when to terminate parity transmission. The other three suboptimal systems do not require full channel information and/or receiver feedback, and hence are more feasible in practice. All four versions can support significantly higher video rates and correspondingly higher quality of decoded video, than prior approaches in the literature, which require full channel information but not feedback.
Seti Detection Strategies for Single Dish Radio Telescopes

Radio Searches for Extra Terrestrial Intelligence aim at detecting artificial transmissions from extra terrestrial communicative civilizations. The lack of prior knowledge concerning these potential transmissions increase the search parameter space. Ground-based single dish radio telescopes offer high sensitivity, but standard data products are limited to power spectral density estimates.To overcome important classical energy detector limitations, two detection strategies based on asynchronous ON and OFF astronomical target observations are proposed. Statistical models are described to enable threshold selection and detection performance assessment.
tau-invariants for knots in rational homology spheres

Ozsvath and Szabo used the knot filtration on CF(S3) to define the τ–invariant for knots in the 3–sphere. We generalize their construction and define a collection of τ–invariants associated to a knot K in a rational homology sphere Y. We then show that some of these invariants provide lower bounds for the genus of a surface with boundary K properly embedded in a negative-definite 4–manifold with boundary Y.
Spectral Line Distortions in the Presence of a Close-in Planet

We discuss the interpretation of the distortions to the stellar spectral lines, with particular attention to line bisectors in the presence of an orbiting planetary companion. We present a simple model whereby light reflected by the companion can cause temporal variations to the observed line profiles. These distortions have a characteristic signature that depends on the inclination angle of the system. For the known close-in extrasolar giant planets, the expected amplitude of the effect might not be far from current detection capabilities. This method could be used to detect the presence of the companion directly, yielding the orbital inclination and hence the planetary mass. Futhermore, a detection would measure a combination of the planetary radius and albedo, from which a minimum radius may be deduced.
Scale dependent alignment between velocity and magnetic field fluctuations in the solar wind and comparisons to Boldyrev's phenomenological theory

A theory of incompressible MHD turbulence recently developed by Boldyrev predicts the existence of a scale dependent angle of alignment between velocity and magnetic field fluctuations that is proportional to the lengthscale of the fluctuations to the power 1/4. In this study, plasma and magnetic field data from the Wind spacecraft are used to investigate the angle between velocity and magnetic field fluctuations in the solar wind as a function of the timescale of the fluctuations and to look for the power law scaling predicted by Boldyrev. Because errors in the velocity vector can create large errors in the angle measurements, particularly at small scales, the angle measurements are suspected to be unreliable except at the largest inertial range scales. For the data at large scales the observed power law exponents range from 0.25 to 0.34, which are somewhat larger than Boldyrev’s prediction of 0.25. The results suggest that the angle may scale like a power law in the solar wind, at least at the largest i...
Computation of the unipotent radical of the differential Galois group for a parameterized second-order linear differential equation

Abstract We propose a new method to compute the unipotent radical R u ( H ) of the differential Galois group H associated to a parameterized second-order homogeneous linear differential equation of the form ∂ 2 ∂ x 2 Y − q Y = 0 , where q ∈ F ( x ) is a rational function in x with coefficients in a Π-field F of characteristic zero, and Π is a commuting set of parametric derivations. The procedure developed by Dreyfus reduces the computation of R u ( H ) to solving a creative telescoping problem, whose effective solution depends on the assumption that the maximal reductive quotient H / R u ( H ) is a Π-constant linear differential algebraic group. When this condition is not satisfied, one can effectively compute a new set of parametric derivations Π ′ such that the associated differential Galois group H ′ has the property that H ′ / R u ( H ′ ) is Π ′ -constant, and such that R u ( H ) is defined by the same differential equations as R u ( H ′ ) . Thus the computation of R u ( H ) is reduced to the effective computation of R u ( H ′ ) . We expect that an elaboration of this method will be successful in extending the applicability of some recent algorithms developed by Minchenko, Ovchinnikov, and Singer to compute unipotent radicals for higher order equations.
LTLf Synthesis on Probabilistic Systems

Many systems are naturally modeled as Markov Decision Processes (MDPs), combining probabilities and strategic actions. Given a model of a system as an MDP and some logical specification of system behavior, the goal of synthesis is to find a policy that maximizes the probability of achieving this behavior. A popular choice for defining behaviors is Linear Temporal Logic (LTL). Policy synthesis on MDPs for properties specified in LTL has been well studied. LTL, however, is defined over infinite traces, while many properties of interest are inherently finite. Linear Temporal Logic over finite traces (LTLf) has been used to express such properties, but no tools exist to solve policy synthesis for MDP behaviors given finite-trace properties. We present two algorithms for solving this synthesis problem: the first via reduction of LTLf to LTL and the second using native tools for LTLf. We compare the scalability of these two approaches for synthesis and show that the native approach offers better scalability compared to existing automaton generation tools for LTL.
Sparse Deep Neural Network Graph Challenge

The MIT/IEEE/Amazon GraphChallenge.org encourages community approaches to developing new solutions for analyzing graphs and sparse data. Sparse AI analytics present unique scalability difficulties. The proposed Sparse Deep Neural Network (DNN) Challenge draws upon prior challenges from machine learning, high performance computing, and visual analytics to create a challenge that is reflective of emerging sparse AI systems. The Sparse DNN Challenge is based on a mathematically well-defined DNN inference computation and can be implemented in any programming environment. Sparse DNN inference is amenable to both vertex-centric implementations and array-based implementations (e.g., using the GraphBLAS.org standard). The computations are simple enough that performance predictions can be made based on simple computing hardware models. The input data sets are derived from the MNIST handwritten letters. The surrounding I/O and verification provide the context for each sparse DNN inference that allows rigorous definition of both the input and the output. Furthermore, since the proposed sparse DNN challenge is scalable in both problem size and hardware, it can be used to measure and quantitatively compare a wide range of present day and future systems. Reference implementations have been implemented and their serial and parallel performance have been measured. Specifications, data, and software are publicly available at GraphChallenge.org.
Design of High-Performance Photon-Number-Resolving Photodetectors Based on Coherently Interacting Nanoscale Elements

A number of applications in basic science and technology would benefit from high-fidelity photon-number-resolving photodetectors. While some recent experimental progress has been made in this direc...
A generic approach to searching for Jacobians

We consider the problem of finding cryptographically suitable Jacobians. By applying a probabilistic generic algorithm to compute the zeta functions of low genus curves drawn from an arbitrary family, we can search for Jacobians containing a large subgroup of prime order. For a suitable distribution of curves, the complexity is subexponential in genus 2, and O(N1/12) in genus 3. We give examples of genus 2 and genus 3 hyperelliptic curves over prime fields with group orders over 180 bits in size, improving previous results. Our approach is particularly effective over low-degree extension fields, where in genus 2 we find Jacobians over Fp2 and trace zero varieties over Fp3 with near-prime orders up to 372 bits in size. For p = 261 1, the average time to find a group with 244-bit near-prime order is under an hour on a PC.
Multiplex Markov chains: Convection cycles and optimality

This paper proposes a multiplex generalization of Markov chains, whereby a set of Markov chain layers is coupled by a set of interlayer Markov chains. The resulting system gives rise to emergent convection cycles that are optimized, along with the convergence rate, when the transition probabilities within and between layers are balanced. The authors support these findings with spectral perturbation theory and an empirical study of frequency-multiplexed brain-activity data.