Results for "Matthew T. Fishman"

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Compression of Correlation Matrices and an Efficient Method for Forming Matrix Product States of Fermionic Gaussian StatesApr 29 2015Here we present an efficient and numerically stable procedure for compressing a correlation matrix into a set of local unitary single-particle gates, which leads to a very efficient way of forming the matrix product state (MPS) approximation of a pure ... More
Wavefunction positivization via automatic differentiationJun 11 2019We introduce a procedure to systematically search for a local unitary transformation that maps a wavefunction with a non-trivial sign structure into a positive-real form. The transformation is parametrized as a quantum circuit compiled into a set of one ... More
Spin Rotation Technique for Non-Collinear Magnetic Systems: Application to the Generalized Villain ModelJan 15 2009Feb 10 2009This work develops a new generalized technique for determining the static and dynamic properties of any non-collinear magnetic system. By rotating the spin operators into the local spin reference frame, we evaluate the zeroth, first, and second order ... More
The Spin State and Spectroscopic Modes of Multiferroic BiFeO3Feb 18 2013Feb 19 2013Spectroscopic modes provide the most sensitive probe of the very weak interactions responsible for the properties of the long-wavelength cycloid in the multiferroic phase of \BF below $\TN \approx 640$ K. Three of the four modes measured by THz and Raman ... More
Spin-Wave Instabilities and Non-Collinear Magnetic Phases of a Geometrically-Frustrated Triangular-Lattice AntiferromagnetJan 15 2009This paper examines the relation between the spin-wave instabilities of collinear magnetic phases and the resulting non-collinear phases for a geometrically-frustrated triangular-lattice antiferromagnet in the high spin limit. Using a combination of phenomenological ... More
Probabilistic analysis of the phase space flow for linear programmingOct 31 2001Feb 24 2004The phase space flow of a dynamical system leading to the solution of Linear Programming (LP) problems is explored as an example of complexity analysis in an analog computation framework. An ensemble of LP problems with $n$ variables and $m$ constraints ... More
Critical Anisotropies of a Geometrically-Frustrated Triangular-Lattice AntiferromagnetFeb 02 2009This work examines the critical anisotropy required for the local stability of the collinear ground states of a geometrically-frustrated triangular-lattice antiferromagnet (TLA). Using a Holstein-Primakoff expansion, we calculate the spin-wave frequencies ... More
Theory of 2$δ$-kicked Quantum RotorsOct 17 2005We examine the quantum dynamics of cold atoms subjected to {\em pairs} of closely spaced $\delta$-kicks from standing waves of light, and find behaviour quite unlike the well-studied quantum kicked rotor (QKR). Recent experiments [Jones et al, {\em Phys. ... More
Probabilistic analysis of a differential equation for linear programmingOct 29 2001Apr 07 2003In this paper we address the complexity of solving linear programming problems with a set of differential equations that converge to a fixed point that represents the optimal solution. Assuming a probabilistic model, where the inputs are i.i.d. Gaussian ... More
Schmidt's Game on Certain FractalsJun 13 2006Nov 10 2010We construct (\alpha ,\beta) and \alpha -winning sets in the sense of Schmidt's game, played on the support of certain measures (very friendly and awfully friendly measures) and show how to derive the Hausdorff dimension for some. In particular we prove ... More
Schmidt's game, Badly Approximable Linear Forms and FractalsSep 11 2008We prove that for every two natural numbers M and N, if Tau is a Borel, finite, absolutely friendly measure on a compact set K of R^MN, then the intersection of K and BA(M,N) is a winning set in Schmidt's game sense played on K, where BA(M,N) is the set ... More
Double Exchange in a Magnetically Frustrated SystemApr 12 2004This work examines the magnetic order and spin dynamics of a double-exchange model with competing ferromagnetic and antiferromagnetic Heisenberg interactions between the local moments. The Heisenberg interactions are periodically arranged in a Villain ... More
The Collinear Magnetic Phases of the Geometrically-Frustrated Antiferromagnet CuFeO$_2$: The Importance of StackingJul 24 2008The correct stacking of hexagonal layers is used to obtain accurate estimates for the exchange and anisotropy parameters of the geometrically-frustrated antiferromagnet CuFeO$_2$. Those parameters are highly constrained by the stability of a collinear ... More
Fractional $\hbar$-scaling for quantum kicked rotors without cantoriFeb 28 2007Oct 19 2007Previous studies of quantum delta-kicked rotors have found momentum probability distributions with a typical width (localization length $L$) characterized by fractional $\hbar$-scaling, ie $L \sim \hbar^{2/3}$ in regimes and phase-space regions close ... More
Identifying the Magnetoelectric Modes of Multiferroic BiFeO$_3$Sep 27 2012We have identified three of the four magnetoelectric modes of multiferroic BiFeO$_3$ measured using THz spectroscopy. Excellent agreement with the observed peaks is obtained by including the effects of easy-axis anisotropy along the direction of the electric ... More
Variational optimization algorithms for uniform matrix product statesJan 24 2017Apr 19 2019We combine the Density Matrix Renormalization Group (DMRG) with Matrix Product State tangent space concepts to construct a variational algorithm for finding ground states of one dimensional quantum lattices in the thermodynamic limit. A careful comparison ... More
Faster Methods for Contracting Infinite 2D Tensor NetworksNov 16 2017Dec 02 2018We revisit the corner transfer matrix renormalization group (CTMRG) method of Nishino and Okunishi for contracting two-dimensional (2D) tensor networks and demonstrate that its performance can be substantially improved by determining the tensors using ... More
A General Relativistic Magnetohydrodynamics Simulation of Jet FormationMar 01 2004Feb 04 2005We have performed a fully three-dimensional general relativistic magnetohydrodynamic (GRMHD) simulation of jet formation from a thin accretion disk around a Schwarzschild black hole with a free-falling corona. The initial simulation results show that ... More
Spin rotation, spin filtering, and spin transfer in directional tunneling through non-centrosymmetric semiconductor barriersJul 08 2008Jan 13 2009We consider spin-dependent tunneling through a gallium arsenide barrier, a material which has no inversion symmetry. We are dealing with free electrons, with one effective mass and a spin-splitting in the barrier material. When we take into account both ... More
Are Abell Clusters Correlated with Gamma-Ray Bursts?Feb 21 1997A recent study has presented marginal statistical evidence that gamma-ray burst sources are correlated with Abell clusters, based on analyses of bursts in the BATSE 3B catalog. Using precise localization information from the 3rd Interplanetary Network, ... More
Metal-insulator transitions in cyclotron resonance of periodic nanostructures due to avoided band crossingsAug 15 2000A recently found metal-insulator transition in a model for cyclotron resonance in a two-dimensional periodic potential is investigated by means of spectral properties of the time evolution operator. The previously found dynamical signatures of the transition ... More
Magnetic dispersion and anisotropy in multiferroic BiFeO3Mar 23 2012Jun 25 2012We have determined the full magnetic dispersion relations of multiferroic BiFeO3. In particular, two excitation gaps originating from magnetic anisotropies have been clearly observed. The direct observation of the gaps enables us to accurately determine ... More
Optical diode effect in the room-temperature multiferroic BiFeO$_3Apr 30 2015Multiferroics permit the magnetic control of the electric polarization and electric control of the magnetization. These static magnetoelectric (ME) effects are of enormous interest: The ability to read and write a magnetic state current-free by an electric ... More
Identifying the multiferroic phase of doped CuFeO_2 using inelastic neutron scatteringJun 02 2010We report inelastic neutron scattering measurements that provide a distinct dynamical "fingerprint" for the multiferroic ground state of 3.5% Ga-doped CuFeO_2. The complex ground state is stabilized by the displacement of the oxygen atoms, which are also ... More
A Resonant-Mode Model of Pulsar Radio EmissionOct 15 2003It is argued that the polar gap and flux tube in the pulsar magnetosphere act as a resonant cavity/waveguide system which is excited by oscillations in the primary beam current and accelerating potential. The modes will be converted, probably scattered, ... More
Trilobites, butterflies, and other exotic specimens of long-range Rydberg moleculesFeb 27 2019This Ph.D. tutorial discusses ultra-long-range Rydberg molecules, the exotic bound states of a Rydberg atom and one or more ground state atoms immersed in the Rydberg electron's wave function. This novel chemical bond is distinct from an ionic or covalent ... More
Terahertz spectroscopy of spin waves in multiferroic BiFeO$_3$ in high magnetic fieldsFeb 11 2013May 24 2013We have studied the magnetic field dependence of far-infrared active magnetic modes in a single ferroelectric domain \BFO/ crystal at low temperature. The modes soften close to the critical field of 18.8\,T along the [001] (pseudocubic) axis, where the ... More
Using Charge Asymmetries to Measure Single Top Quark Production at the LHCMar 11 2005Electroweak production of single top quarks is an as-yet-unverified prediction of the Standard model, potentially sensitive to new physics. Two of the single top quark productions channels have significant charge asymmetries at the LHC, while the much ... More
The Generalized Asymptotic Equipartition Property: Necessary and Sufficient ConditionsNov 16 2007Suppose a string $X_1^n=(X_1,X_2,...,X_n)$ generated by a memoryless source $(X_n)_{n\geq 1}$ with distribution $P$ is to be compressed with distortion no greater than $D\geq 0$, using a memoryless random codebook with distribution $Q$. The compression ... More
Speeding up low-mass planetary microlensing simulations and modelling: the Caustic Region Of INfluenceNov 05 2013Nov 25 2014Extensive simulations of planetary microlensing are necessary both before and after a survey is conducted: before to design and optimize the survey and after to understand its detection efficiency. The major bottleneck in such computations is the computation ... More
Riesz s-Equilibrium Measures on d-Dimensional Fractal Sets as s Approaches dMay 13 2009Let $A$ be a compact set in $\Rp$ of Hausdorff dimension $d$. For $s\in(0,d)$, the Riesz $s$-equilibrium measure $\mu^{s,A}$ is the unique Borel probability measure with support in $A$ that minimizes $$ \Is(\mu):=\iint\Rk{x}{y}{s}d\mu(y)d\mu(x)$$ over ... More
Integration on product spaces and GL_n of a valuation field over a local fieldDec 13 2007We present elements of a theory of translation-invariant integration on finite dimensional vector spaces and on GL_n over a valuation field with local field as residue field. We then discuss the case of an arbitrary algebraic group. This extends the work ... More
Integration on valuation fields over local fieldsDec 13 2007We present elements of a theory of translation-invariant integration, measure, and harmonic analysis on a valuation field with local field as residue field. This extends the work of Fesenko. Applications to zeta integrals for two-dimensional local fields ... More
A Dynamic Programming Approach for Approximate Uniform Generation of Binary Matrices with Specified MarginsJun 04 2009Jan 25 2013Consider the collection of all binary matrices having a specific sequence of row and column sums and consider sampling binary matrices uniformly from this collection. Practical algorithms for exact uniform sampling are not known, but there are practical ... More
Conservative Hypothesis Tests and Confidence Intervals using Importance SamplingApr 16 2010Apr 08 2011Importance sampling is a common technique for Monte Carlo approximation, including Monte Carlo approximation of p-values. Here it is shown that a simple correction of the usual importance sampling p-values creates valid p-values, meaning that a hypothesis ... More
Homotopy Loday Algebras and Symplectic $2$-ManifoldsApr 09 2018Using the technique of higher derived brackets developed by Voronov, we construct a homotopy Loday algebra in the sense of Ammar and Poncin associated to any symplectic $2$-manifold. The algebra we obtain has a particularly nice structure, in that it ... More
Duchamp: a 3D source finder for spectral-line dataJan 13 2012This paper describes the Duchamp source finder, a piece of software designed to find and describe sources in 3-dimensional, spectral-line data cubes. Duchamp has been developed with HI (neutral hydrogen) observations in mind, but is widely applicable ... More
A sequence of discrete minimal energy configurations that does not converge in the weak-star topologySep 20 2011We demonstrate a set A and a value of s for which the sequence of N-point discrete minimal Riesz s-energy configurations on A does not have an asymptotic distribution in the weak-star sense as N tends to infinity.
Pressure-Induced Enhancement of the Magnetic Anisotropy in Mn(N(CN)$_{2}$)$_{2}$Dec 07 2014Using dc and ac magnetometry, the pressure dependence of the magnetization of the three-dimensional antiferromagnetic coordination polymer Mn(N(CN)$_{2}$)$_{2}$ was studied up to 12 kbar and down to 8K. The magnetic transition temperature, $T_c$, increases ... More
Magnetic Interaction in the Geometrically Frustrated Triangular Lattice Antiferromagnet $\rm CuFeO_2$Aug 09 2007Oct 08 2007The spin wave excitations of the geometrically frustrated triangular lattice antiferromagnet (TLA) $\rm CuFeO_2$ have been measured using high resolution inelastic neutron scattering. Antiferromagnetic interactions up to third nearest neighbors in the ... More
Is transport in time-dependent random potentials universal ?Mar 30 2012The growth of the average kinetic energy of classical particles is studied for potentials that are random both in space and time. Such potentials are relevant for recent experiments in optics and in atom optics. It is found that for small velocities uniform ... More
Effective noise theory for the Nonlinear Schrödinger Equation with disorderAug 30 2011Feb 07 2012For the Nonlinear Shr\"odinger Equation with disorder it was found numerically that in some regime of the parameters Anderson localization is destroyed and subdiffusion takes place for a long time interval. It was argued that the nonlinear term acts as ... More
Dynamics of an ion chain in a harmonic potentialJul 26 2004Cold ions in anisotropic harmonic potentials can form ion chains of various sizes. Here, the density of ions is not uniform, thus the eigenmodes are not phononic-like waves. We study chains of N>>1 ions and evaluate analytically the long wavelength modes ... More
Relaxation and Diffusion for the Kicked RotorOct 28 1999The dynamics of the kicked-rotor, that is a paradigm for a mixed system, where the motion in some parts of phase space is chaotic and in other parts is regular is studied statistically. The evolution (Frobenius-Perron) operator of phase space densities ... More
Intrinsic approximation for fractals defined by rational iterated function systems - Mahler's research suggestionAug 10 2012Jul 26 2014Following K. Mahler's suggestion for further research on intrinsic approximation on the Cantor ternary set, we obtain a Dirichlet type theorem for the limit sets of rational iterated function systems. We further investigate the behavior of these approximation ... More
Variations on Dirichlet's theoremMar 07 2015We give a necessary and sufficient condition for the following property of an integer $d\in\mathbb N$ and a pair $(a,A)\in\mathbb R^2$: There exist $\kappa > 0$ and $Q_0\in\mathbb N$ such that for all $\mathbf x\in \mathbb R^d$ and $Q\geq Q_0$, there ... More
Scaling Properties of Weak Chaos in Nonlinear Disordered LatticesJul 23 2010Sep 16 2010The Discrete Nonlinear Schroedinger Equation with a random potential in one dimension is studied as a dynamical system. It is characterized by the length, the strength of the random potential and by the field density that determines the effect of nonlinearity. ... More
The Ulysses Supplement to the BATSE 4Br Catalog of Cosmic Gamma-Ray BurstsDec 01 1998We present Interplanetary Network localization information for 147 gamma-ray bursts observed by the Burst and Transient Source Experiment between the end of the 3rd BATSE catalog and the end of the 4th BATSE catalog, obtained by analyzing the arrival ... More
The Ulysses Supplement to the BATSE 3B Catalog of Cosmic Gamma-Ray BurstsNov 30 1998We present Interplanetary Network localization information for 218 gamma-ray bursts in the 3rd BATSE catalog, obtained by analyzing the arrival times of these bursts at the Ulysses and Compton Gamma-Ray Observatory (CGRO) spacecraft. For any given burst ... More
Semiclassical analysis of Bose-Hubbard dynamicsSep 17 2014In this work the two site Bose-Hubbard model is studied analytically in the limit of weak coupling u and large number of particles N . The semiclassical approximation where \frac{1}{N} plays the role of Planck's constant was used and perturbation theory ... More
Field dependence of the Spin State and Spectroscopic Modes of Multiferroic BiFeO$_3$Apr 15 2013Jul 26 2013The spectroscopic modes of multiferroic BiFeO$_3$ provide detailed information about the very small anisotropy and Dzyaloshinskii-Moriya (DM) interactions responsible for the long-wavelength, distorted cycloid below $\TN = 640$ K. A microscopic model ... More
Relaxation and Noise in Chaotic SystemsApr 29 2002For a class of idealized chaotic systems (hyperbolic systems) correlations decay exponentially in time. This result is asymptotic and rigorous. The decay rate is related to the Ruelle-Pollicott resonances. Nearly all chaotic model systems, that are studied ... More
Excitation of Small Quantum Systems by High-Frequency FieldsMay 20 1996The excitation by a high frequency field of multi--level quantum systems with a slowly varying density of states is investigated. A general approach to study such systems is presented. The Floquet eigenstates are characterized on several energy scales. ... More
Spectral Statistics of Rectangular Billiards with Localized PerturbationsNov 28 2001Oct 02 2002The form factor $K(\tau)$ is calculated analytically to the order $\tau^3$ as well as numerically for a rectangular billiard perturbed by a $\delta$-like scatterer with an angle independent diffraction constant, $D$. The cases where the scatterer is at ... More
The possibility of a metal insulator transition in antidot arrays induced by an external drivingAug 13 1999It is shown that a family of models associated with the kicked Harper model is relevant for cyclotron resonance experiments in an antidot array. For this purpose a simplified model for electronic motion in a related model system in presence of a magnetic ... More
The Microscopic Model of BiFeO$_3$Aug 16 2017Many years and great effort have been spent constructing the microscopic model for the room temperature multiferroic BiFeO3 However, earlier models implicitly assumed that the cycloidal wavevector q was confined to one of the three-fold symmetric axis ... More
Magnetic Susceptibility of the Double-Exchange Model in the RKKY LimitJun 27 2006The magnetic susceptibility and Edwards-Anderson order parameter q of the spin-glass-like (SGL) phase of the double-exchange model are evaluated in the weak-coupling or RKKY limit. Dynamical mean-field theory is used to show that q=M(T/Tsg)^2, where M ... More
Multiscale time averaging, ReloadedJul 04 2012Aug 15 2013We develop a rigorously controlled multi-time scale averaging technique; the averaging is done on a finite time interval, properly chosen, and then, via iterations and normal form transformations, the time intervals are scaled to arbitrary order. Here, ... More
Eigenmodes and thermodynamics of a Coulomb chain in a harmonic potentialFeb 18 2004The density of ions trapped in a harmonic potential in one dimension is not uniform. Consequently the eigenmodes are not phonons. We calculate the long wavelength modes in the continuum limit, and evaluate the density of states in the short wavelength ... More
Diffusion For Ensembles of Standard MapsSep 17 2014Aug 18 2015Two types of random evolution processes are studied for ensembles of the standard map with driving parameter $K$ that determines its degree of stochasticity. For one type of processes the parameter $K$ is chosen at random from a Gaussian distribution ... More
Collapses and revivals of matter wavesAug 27 2014Jan 27 2015Quantum collapses and revivals are fascinating manifestations of interference. Of particular interest in recent years are macroscopic quantum interference effects in Bose-Einstein condensates. In this letter such effects will be studied for the two site ... More
Statistical Properties of the one dimensional Anderson model relevant for the Nonlinear Schrödinger Equation in a random potentialJun 05 2012The statistical properties of overlap sums of groups of four eigenfunctions of the Anderson model for localization as well as combinations of four eigenenergies are computed. Some of the distributions are found to be scaling functions, as expected from ... More
Spin Dynamics of a Canted Antiferromagnet in a Magnetic FieldFeb 25 2004Jun 17 2004The spin dynamics of a canted antiferromagnet with a quadratic spin-wave dispersion near $\vq =0$ is shown to possess a unique signature. When the anisotropy gap is negligible, the spin-wave stiffness $\dsw (\vq, B) = (\omega_{\vq}-B)/q^2$ depends on ... More
Localized Perturbations of Integrable SystemsNov 28 2001The statistics of energy levels of a rectangular billiard, that is perturbed by a strong localized potential, are studied analytically and numerically, when this perturbation is at the center or at a typical position. Different results are found for these ... More
Effects of interactions on the dynamics of driven cold atomsApr 10 2014Aug 27 2014The quantum fidelity was introduced by Peres to study some fingerprints of classically chaotic behavior in the quantum dynamics of the corresponding systems. In the present paper the signatures of classical dynamics near elliptic points and of interactions ... More
The Localization Length of Stationary States in the Nonlinear Schreodinger EquationMay 16 2007Sep 16 2007For the nonlinear Schreodinger equation (NLSE), in presence of disorder, exponentially localized stationary states are found. In the present Letter it is demonstrated analytically that the localization length is typically independent of the strength of ... More
Transport in time-dependent random potentialsMar 30 2012The classical dynamics in stationary potentials that are random both in space and time is studied. It can be intuitively understood with the help of Chirikov resonances that are central in the theory of Chaos, and explored quantitatively in the framework ... More
Spin Dynamics of Double-Exchange Manganites with Magnetic FrustrationFeb 12 2004This work examines the effects of magnetic frustration due to competing ferromagnetic and antiferromagnetic Heisenberg interactions on the spin dynamics of the double-exchange model. When the local moments are non-colinear, a charge-density wave forms ... More
Pinning, Rotation, and Metastability of BiFeO$_3$ Cycloidal Domains in a Magnetic FieldSep 05 2017Sep 07 2017Earlier models for the room-temperature multiferroic BiFeO3 implicitly assumed that a very strong anisotropy restricts the domain wavevectors q to the three-fold symmetric axis normal to the static polarization P. However, recent measurements demonstrate ... More
Unconventional height functions in simultaneous Diophantine approximationJan 31 2014Apr 13 2016Simultaneous Diophantine approximation is concerned with the approximation of a point $\mathbf x\in\mathbb R^d$ by points $\mathbf r\in\mathbb Q^d$, with a view towards jointly minimizing the quantities $\|\mathbf x - \mathbf r\|$ and $H(\mathbf r)$. ... More
Orientation Dependence of the Critical Magnetic Field for Multiferroic BiFeO$_3$Jul 26 2013Multiferroic BiFeO3 undergoes a transition from a distorted spiral phase to a G-type antiferromagnet above a critical field H_c that depends on the orientation m of the field. We show that H_c(m) has a maximum when oriented along a cubic diagonal parallel ... More
A generalized Lieb-Liniger modelAug 09 2015Nov 19 2015In 1963, Lieb and Liniger solved exactly a one dimensional model of bosons interacting by a repulsive \delta-potential and calculated the ground state in the thermodynamic limit. In the present work, we extend this model to a potential of three \delta-functions, ... More
Slowly changing potential problems in Quantum Mechanics: Adiabatic Theorems, Ergodic Theorems, and ScatteringJan 06 2015We employ the recently developed multi-time scale averaging method to study the large time behavior of slowly changing (in time) Hamiltonians. We treat some known cases in a new way, such as the Zener problem, and we give another proof of the Adiabatic ... More
Extrinsic Diophantine approximation on manifolds and fractalsJun 03 2014Jan 10 2015Fix $d\in\mathbb N$, and let $S\subseteq\mathbb R^d$ be either a real-analytic manifold or the limit set of an iterated function system (for example, $S$ could be the Cantor set or the von Koch snowflake). An $extrinsic$ Diophantine approximation to a ... More
Linear algebraic techniques for spanning tree enumerationMar 12 2019Kirchhoff's Matrix-Tree Theorem asserts that the number of spanning trees in a finite graph can be computed from the determinant of any of its reduced Laplacian matrices. In many cases, even for well-studied families of graphs, this can be computationally ... More
Linear algebraic techniques for weighted spanning tree enumerationFeb 27 2019The weighted spanning tree enumerator of a graph $G$ with weighted edges is the sum of the products of edge weights over all the spanning trees in $G$. In the special case that all of the edge weights equal $1$, the weighted spanning tree enumerator counts ... More
Robust Execution of Contact-Rich Motion Plans by Hybrid Force-Velocity ControlMar 07 2019In hybrid force-velocity control, the robot can use velocity control in some directions to follow a trajectory, while performing force control in other directions to maintain contacts with the environment regardless of positional errors. We call this ... More
Sub-nanosecond Electro-optic Modulation of Triggered Single Photons from a Quantum DotMar 18 2011Control of single photon wave-packets is an important resource for developing hybrid quantum systems which are composed of different physical systems interacting via photons. Here we extend this control to triggered photons emitted by a quantum dot, temporally ... More
Linear algebraic techniques for spanning tree enumerationMar 12 2019Apr 16 2019Kirchhoff's Matrix-Tree Theorem asserts that the number of spanning trees in a finite graph can be computed from the determinant of any of its reduced Laplacian matrices. In many cases, even for well-studied families of graphs, this can be computationally ... More
Convergence Rate Estimates for Consensus over Random GraphsOct 21 2016Mar 21 2017Multi-agent coordination algorithms with randomized interactions have seen use in a variety of settings in the multi-agent systems literature. In some cases, these algorithms can be random by design, as in a gossip-like algorithm, and in other cases they ... More
Gross Spectral Differences between Bright and Dim Gamma-Ray BurstsAug 15 1994We find that dim gamma-ray bursts (GRBs) are softer than bright GRBs, as indicated on average by data from the Burst and Transient Source Experiment (BATSE) on board the Compton Gamma Ray Observatory. We show that this correlation is statistically significant ... More
The Interplanetary Network Supplement to the BATSE 5B Catalog of Cosmic Gamma-Ray BurstsMay 30 2006Aug 18 2011We present Interplanetary Network (IPN) localization information for 343 gamma-ray bursts observed by the Burst and Transient Source Experiment (BATSE) between the end of the 4th BATSE catalog and the end of the Compton Gamma-Ray Observatory (CGRO) mission, ... More
Magnetic quantum phase transition in an anisotropic Kondo latticeJul 21 2006Dec 03 2007The quantum phase transition between paramagnetic and antiferromagnetic phases of the Kondo lattice model with Ising anisotropy in the intersite exchange is studied within the framework of extended dynamical mean-field theory. Nonperturbative numerical ... More
Numerical renormalization-group study of the Bose-Fermi Kondo modelJan 25 2005Aug 11 2005We extend the numerical renormalization-group method to Bose-Fermi Kondo models (BFKMs), describing a local moment coupled to a conduction band and a dissipative bosonic bath. We apply the method to the Ising-symmetry BFKM with a bosonic bath spectral ... More
Carrier-induced ferromagnetism in p-Zn1-xMnxTeJul 31 2000We present a systematic study of the ferromagnetic transition induced by the holes in nitrogen doped Zn1-xMnxTe epitaxial layers, with particular emphasis on the values of the Curie-Weiss temperature as a function of the carrier and spin concentrations. ... More
Kondo physics and dissipation: A numerical renormalization-group approach to Bose-Fermi Kondo modelsSep 22 2006Sep 25 2006We extend the numerical renormalization-group method to treat Bose-Fermi Kondo models (BFKMs) describing a local moment coupled both to a conduction band and to a dissipative bosonic bath representing, e.g., lattice or spin collective excitations of the ... More
Correlation and Simpson conversion in $2 \times 2 \times 2$ contingency tablesSep 12 2018We study a generalisation of Simpson reversal (also known as Simpson's paradox or the Yule-Simpson effect) to $2 \times 2 \times 2$ contingency tables and characterise the cases for which it can and cannot occur with two combinatorial-geometric lemmas. ... More
Convergence Rate Estimates for Consensus over Random GraphsOct 21 2016Multi-agent coordination algorithms with randomized interactions have seen use in a variety of settings in the multi-agent systems literature. In some cases, these algorithms can be random by design, as in a gossip-like algorithm, and in other cases they ... More
Graded Betti numbers of cycle graphs and standard Young tableauxApr 04 2015We give a bijective proof that the Betti numbers of a minimal free resolution of the Stanley-Reisner ring of a cycle graph (viewed as a one-dimensional simplicial complex) are given by the number of standard Young tableaux of a given shape.
Evaluating Throwing Ability in BaseballMay 22 2007Jun 01 2007We present a quantitative analysis of throwing ability for major league outfielders and catchers. We use detailed game event data to tabulate success and failure events in outfielder and catcher throwing opportunities. We attribute a run contribution ... More
Duration Distributions of Bright and Dim BATSE Gamma-Ray BurstsAug 17 1994We have measured the T90 and T50 durations of bright and dim gamma-ray bursts (GRBs) detected by the Compton Gamma Ray Observatory's Burst and Transient Source Experiment (BATSE). The T90 (T50) duration is defined as the interval over which 5\% (25\%) ... More
Detection of Signature Consistent with Cosmological Time Dilation in Gamma-Ray BurstsDec 21 1993If gamma-ray bursters are at cosmological distances - as suggested by their isotropic distribution on the sky and by their number-intensity relation - then the burst profiles will be stretched in time, by an amount proportional to the redshift, 1 + $z$. ... More
Exact Eigenfunctions of a Chaotic SystemJul 26 1997The interest in the properties of quantum systems, whose classical dynamics are chaotic, derives from their abundance in nature. The spectrum of such systems can be related, in the semiclassical approximation (SCA), to the unstable classical periodic ... More
Carrier induced ferromagnetic interactions in p-doped Zn(1-x)MnxTe epilayersOct 08 1999p-type doping of molecular-beam-epitaxy grown layers of the diluted magnetic semiconductor Zn(1-x)MnxTe is achieved by using an active nitrogen cell. The strong interaction between the localized Mn spins and the holes deeply modifies the transport properties ... More
Null Result in Gamma-Ray Burst Lensed Echo SearchMar 22 1994We have searched for gravitational-lens induced echoes between gamma-ray bursts (GRBs) in NASA's orbiting {\it Compton} Gamma Ray Observatory's Burst and Transient Source Experiment (BATSE) data. The search was conducted in two phases. In the first phase ... More
Extended Power-Law Decays in BATSE Gamma-Ray Bursts: Signatures of External Shocks?Jan 29 2002The connection between Gamma-Ray Bursts (GRBs) and their afterglows is currently not well understood. Afterglow models of synchrotron emission generated by external shocks in the GRB fireball model predict emission detectable in the gamma-ray regime ($\gax ... More
Hybrid Quantum-Classical Monte-Carlo Study of a Molecule-Based MagnetSep 05 2008Using a Monte Carlo (MC) method, we study an effective model for the Fe(II)Fe(III) bimetallic oxalates. Within a hybrid quantum-classical MC algorithm, the Heisenberg S=2 and $S'=5/2$ spins on the Fe(II) and Fe(III) sites are updated using a quantum MC ... More
The Quantum-Classical Crossover in the Adiabatic Response of Chaotic SystemsOct 10 1999The autocorrelation function of the force acting on a slow classical system, resulting from interaction with a fast quantum system is calculated following Berry-Robbins and Jarzynski within the leading order correction to the adiabatic approximation. ... More
A Spiral Spin State with Open Boundary Conditions in a Magnetic FieldApr 24 2017In order to model a spiral spin state in a thin film, we study a classical Heisenberg model with open boundary conditions. With magnetic field applied in the plane of the film, the spin state becomes ferromagnetic above a critical field that increases ... More
Localization of eigenstates in a modified Tomonaga-Luttinger modelJun 06 2000We study the localization in the Hilbert space of a modified Tomonaga-Luttinger model. For the standard version of this model, the states are found to be extended in the basis of Slater determinants, representing the eigenstates of the non-interacting ... More