Results for "Michael Tovar"

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Laue three dimensional neutron diffractionFeb 08 2019This article presents a measurement technique and data analysis tool to perform 3D grain distribution mapping and indexing of oligocrystalline samples using neutrons: Laue three-dimensional neutron diffraction (Laue3DND). The approach builds on forward ... More
Brane world in Non-Riemannian GeometryDec 12 2012We carefully investigate the modified Einstein's field equation in a four dimensional (3-brane) arbitrary manifold embedded in a five dimensional Non-Riemannian bulk spacetime with a noncompact extra dimension. In this context the Israel-Darmois matching ... More
Double Exchange in Electron Doped Ca1-xYxMnO3 ManganitesOct 19 2000Sep 13 2001We have studied structural, magnetic and transport properties as a function of temperature and magnetic field in the electron doped manganite YxCa1-xMnO3, for 0<x<0.25. We found that in the paramagnetic regime, the magnetic susceptibility, \chi, deviates ... More
Dzyaloshinskii-Moriya interactions in valence bond systemsSep 01 2008Oct 22 2008We investigate the effect of Dzyaloshinskii-Moriya interactions on the low temperature magnetic susceptibility for a system whose low energy physics is dominated by short-range valence bonds (singlets). Our general perturbative approach is applied to ... More
Magnetic polarons in Ca_(1-x)Y_xMnO_3Aug 17 2001Experimental evidence show that in the magnetoresistive manganite Ca_(1-x) Y_xMnO_3, ferromagnetic (FM) polarons arises in an antiferromagnetic (AF) background, as a result of the doping with Yttrium. This hypothesis is supported in this work by classical ... More
Towards a Realistic Simulation Framework for Vehicular Platooning ApplicationsApr 05 2019Cooperative vehicle platooning applications increasingly demand realistic simulation tools to ease their validation and to bridge the gap between development and real-world deployment. However, their complexity and cost often hinder its validation in ... More
Discovery of potential collaboration networks from open knowledge sourcesNov 08 2017Scientific publishing conveys the outputs of an academic or research activity, in this sense; it also reflects the efforts and issues in which people engage. To identify potential collaborative networks one of the simplest approaches is to leverage the ... More
Wheeler-DeWitt quantization and singularitiesJan 17 2015We consider a Bohmian approach to the Wheeler-DeWitt quantization of the Friedmann-Lemaitre-Robertson-Walker model and investigate the question whether or not there are singularities, in the sense that the universe reaches zero volume. We find that for ... More
Very long-range attractive and repulsive forces in Model Colloidal DispersionsDec 08 2018Experiments with polymer latex solutions show the coexistence of order-disorder structures of macroions. Because of the large macroions' sizes, this order-disorder phase coexistence imply the existence of very long-range attractive and repulsive forces, ... More
LCD: Low Latency Command Dissemination for A Platoon of VehiclesJan 18 2018In a vehicular platoon, a lead vehicle that is responsible for managing the platoon's moving directions and velocity periodically disseminates control commands to following vehicles based on vehicle-to-vehicle communications. However, reducing command ... More
Full Optical Fiber Link Characterization with the BSS-LassoJun 08 2018Dec 29 2018Manipulation of the detected backscattered Rayleigh signal inside the bandwidth of a frequency-swept optical sub-carrier propagating into an optical fiber permits an efficient localization of faults through a Fourier operator. When the bandwidth is restricted, ... More
Overcharging: The Crucial Role of Excluded VolumeNov 19 2001Aug 05 2002In this Letter we investigate the mechanism for overcharging of a single spherical colloid in the presence of aqueous salts within the framework of the primitive model by molecular dynamics (MD) simulations as well as integral-equation theory. We find ... More
The electrical double layer for a fully asymmetric electrolyte around a spherical colloid: an integral equation studyDec 17 2004The hypernetted chain/mean spherical approximation (HNC/MSA) integral equation is obtained and solved numerically for a totally asymmetric primitive model electrolyte around a spherical macroparticle. The ensuing radial distribution functions show a very ... More
Alignment-free characterization of polarizing beamsplittersMar 17 2019Traditional methods for measurement of Polarizing Beamsplitter (PBS) parameters, especially the extinction ratio, require highly polarized light sources, alignment procedures and/or experimental parameters that change over time, such as polarization rotations. ... More
Long-range overcharging and long-range charge reversal in model colloidal dispersionsDec 01 2017Most theoretical and simulation studies on charged particles suspensions are at infinite dilution conditions. Hence these studies have been focused on the electrolyte structure around an isolated central particle (or elctrode), where phenomena as charge ... More
Mixed-criticality Scheduling with Dynamic Redistribution of Shared CacheApr 28 2017The design of mixed-criticality systems often involvespainful tradeoffs between safety guarantees and performance.However, the use of more detailed architectural modelsin the design and analysis of scheduling arrangements for mixedcriticalitysystems can ... More
Charge disproportionation in YNiO$_{3}$ : ESR and susceptibility studyNov 28 2002We present a study of the magnetic properties of YNiO$_{3}$ in the paramagnetic range, above and below the metal-insulator (MI) transition. The dc susceptibility, $\chi_{dc}$ (measured up to 1000 K) is a decreasing function of T for $T >$150 K (the N\'{e}el ... More
Feasibility of non-invasive optical blood-glucose detection using overtone circular dichroismJan 22 2016Diabetes is one of the most debilitating and costly diseases currently plaguing humanity. It is a leading cause of death and dismemberment in the world, and we know how to treat it. Accurate, continuous monitoring and control of blood glucose levels via ... More
Open Mobile API: Accessing the UICC on Android DevicesJan 12 2016This report gives an overview of secure element integration into Android devices. It focuses on the Open Mobile API as an open interface to access secure elements from Android applications. The overall architecture of the Open Mobile API is described ... More
On Covert Acoustical Mesh Networks in AirJun 04 2014Covert channels can be used to circumvent system and network policies by establishing communications that have not been considered in the design of the computing system. We construct a covert channel between different computing systems that utilizes audio ... More
Root Refinement for Real PolynomialsApr 07 2011Jun 12 2013We consider the problem of approximating all real roots of a square-free polynomial $f$. Given isolating intervals, our algorithm refines each of them to a width of $2^{-L}$ or less, that is, each of the roots is approximated to $L$ bits after the binary ... More
A natural probability measure derived from Stern's diatomic sequenceJun 01 2017Mar 15 2018Stern's diatomic sequence with its intrinsic repetition and refinement structure between consecutive powers of $2$ gives rise to a rather natural probability measure on the unit interval. We construct this measure and show that it is purely singular continuous, ... More
An algorithm for quantifying dependence in multivariate data setsJul 04 2012Sep 27 2012We describe an algorithm to quantify dependence in a multivariate data set. The algorithm is able to identify any linear and non-linear dependence in the data set by performing a hypothesis test for two variables being independent. As a result we obtain ... More
Logic Programming with Graph Automorphism: Integrating naut with Prolog (Tool Description)Jul 17 2016Aug 01 2016This paper presents the plnauty~library, a Prolog interface to the nauty graph-automorphism tool. Adding the capabilities of nauty to Prolog combines the strength of the "generate and prune" approach that is commonly used in logic programming and constraint ... More
Slow Steady-Shear of Plastic Bead RaftsOct 12 2004Experimental measurements of the response of a two dimensional system of plastic beads subjected to steady shear are reported. The beads float at the surface of a fluid substrate and are subjected to a slow, steady-shear in a Couette geometry. The flow ... More
Asymmetric response of a jammed plastic bead raftMay 18 2006Fluctuation-dissipation relations have received significant attention as a potential method for defining an effective temperature in nonequilibrium systems. The successful development of an effective temperature would be an important step in the application ... More
Examples of nonpolygonal limit shapes in i.i.d. first-passage percolation and infinite coexistence in spatial growth modelsSep 13 2010Mar 13 2013We construct an edge-weight distribution for i.i.d. first-passage percolation on $\mathbb{Z}^2$ whose limit shape is not a polygon and whose extreme points are arbitrarily dense in the boundary. Consequently, the associated Richardson-type growth model ... More
Interface dynamics in discrete forward-backward diffusion equationsApr 05 2013We study the motion of phase interfaces in a diffusive lattice equation with bistable nonlinearity and derive a free boundary problem with hysteresis to describe the macroscopic evolution in the parabolic scaling limit. The first part of the paper deals ... More
Group analysis of differential equations and generalized functionsDec 28 1999We present an extension of the methods of classical Lie group analysis of differential equations to equations involving generalized functions (in particular: distributions). A suitable framework for such a generalization is provided by Colombeau's theory ... More
What the characters of irreducible subrepresentations of Jordan cells can tell us about LCFTJul 22 2013Jan 04 2014In this article, we review some aspects of logarithmic conformal field theories which can be inferred from the characters of irreducible submodules of indecomposable modules. We will mainly consider the W(2,2p-1,2p-1,2p-1) series of triplet algebras and ... More
A Worst-case Bound for Topology Computation of Algebraic CurvesApr 08 2011Computing the topology of an algebraic plane curve $\mathcal{C}$ means to compute a combinatorial graph that is isotopic to $\mathcal{C}$ and thus represents its topology in $\mathbb{R}^2$. We prove that, for a polynomial of degree $n$ with coefficients ... More
Comparison between step strains and slow steady shear in a bubble raftDec 20 2004We report on a comparison between stress relaxations after an applied step strain and stress relaxations during slow, continuous strain in a bubble raft. A bubble raft serves as a model two-dimensional foam and consists of a single layer of bubbles on ... More
Evaluation of Contactless Smartcard AntennasJul 23 2015This report summarizes the results of our evaluation of antennas of contactless and dual interface smartcards and our ideas for user-switchable NFC antennas. We show how to disassemble smartcards with contactless capabilities in order to obtain the bare ... More
A Variant of K-theory: K_{+-}Feb 11 2003We describe a variant of K-theory for spaces with involution, built from vector bundles which are sent to their negative under the involution.
The periodic Floer homology of a Dehn twistOct 04 2004May 02 2005The periodic Floer homology of a surface symplectomorphism, defined by the first author and M. Thaddeus, is the homology of a chain complex which is generated by certain unions of periodic orbits, and whose differential counts certain embedded pseudoholomorphic ... More
CPT and Other Symmetries in String/M TheorySep 20 2004Feb 05 2005We initiate a search for non-perturbative consistency conditions in M theory. Some non-perturbative conditions are already known in Type I theories; we review these and search for others. We focus principally on possible anomalies in discrete symmetries. ... More
Linear programming methods for exponential dominationJan 19 2018For a graph $G,$ we consider $D \subset V(G)$ to be a porous exponential dominating set if $1 \le \sum_{d \in D}$ $\left( \tfrac{1}{2} \right)^{dist(d,v) -1}$ for every $v \in V(G),$ where $dist(d,v)$ denotes the length of the shortest $dv$ path. The ... More
Scaling of the diffraction measure of $k$-free integers near the originMar 30 2019Asymptotics are derived for the scaling of the total diffraction intensity for the set of $k$-free integers near the origin, which is a measure for the degree of patch fluctuations.
On exponential domination of the consecutive circulant graphDec 14 2017For a graph $G,$ we consider $D \subset V(G)$ to be a porous exponential dominating set if $1\le \sum_{d \in D}$ $\left( \frac{1}{2} \right)^{\text{dist}(d,v) -1}$ for every $v \in V(G),$ where dist$(d,v)$ denotes the length of the smallest $dv$ path. ... More
The role of blood circulatory system in thermal regulation of animals explained by entropy production analysisAug 16 2013A novel model of thermal regulation of homoeothermic animals has been implemented. The model is based on a non-equilibrium thermodynamic approach which introduces entropy balance and the rate of entropy generation as a formulation of The Second Law. The ... More
Hysteresis and phase transitions in a lattice regularization of an ill-posed forward-backward diffusion equationOct 18 2016We consider a lattice regularization for an ill-posed diffusion equation with trilinear constitutive law and study the dynamics of phase interfaces in the parabolic scaling limit. Our main result guarantees for a certain class of single-interface initial ... More
Stopping Active Learning based on Predicted Change of F Measure for Text ClassificationJan 26 2019During active learning, an effective stopping method allows users to limit the number of annotations, which is cost effective. In this paper, a new stopping method called Predicted Change of F Measure will be introduced that attempts to provide the users ... More
Hysteresis and phase transitions in a lattice regularization of an ill-posed forward-backward diffusion equationOct 18 2016Aug 06 2017We consider a lattice regularization for an ill-posed diffusion equation with trilinear constitutive law and study the dynamics of phase interfaces in the parabolic scaling limit. Our main result guarantees for a certain class of single-interface initial ... More
A note on Neumann problems on graphsMar 22 2018We discuss Neumann problems for self-adjoint Laplacians on (possibly infinite) graphs. Under the assumption that the heat semigroup is ultracontractive we discuss the unique solvability for non-empty subgraphs with respect to the vertex boundary and provide ... More
High temperature susceptibility in electron doped Ca1-xYxMnO3: Double Exchange vs SuperexchangeNov 12 2002We present a study of the magnetic properties of the electron doped manganites Ca1-xYxMnO3 (for 0<=x<=0.25) in the paramagnetic regime. For the less doped samples (x<=0.1) the magnetic susceptibility, c(T), follows a Curie-Weiss (CW) law only for T > ... More
R-M interactions in R2BaMO5 (R=Y or Gd and M=Cu or Zn)Feb 26 2013R2BaMO5 (R = Gd, Y and M = Cu, Zn) oxides have been studied by specific heat, dc magnetic susceptibility, and electron paramagnetic resonance (EPR). For one member of the series without magnetic moment at M, namely Gd2BaZnO5, measurements reveal long ... More
Magnetic phase transition in CoO confined to a vycor type porous glass. Neutron diffraction studyJun 20 2005Neutron diffraction studies of antiferromagnetic CoO confined to a vycor type porous glass demonstrate a continuous magnetic phase transition with a decreased N\'eel temperature and reduced magnetic moment as compared with the bulk.
Conserved charges and soliton solutions in affine Toda theoryAug 16 1994Nov 07 1994We study the conserved charges of affine Toda field theories by making use of the conformally invariant extension of these theories. We compute the values of all charges for the single soliton solutions, and show that these are related to eigenvectors ... More
Lusternik-Schnirelman theory for closed 1-formsNov 18 1998S.P.Novikov developed an analog of the Morse theory for closed 1-forms. In this paper I suggest an analog of the Lusternik - Schnirelman theory for closed 1-forms.
Homological algebra of Novikov-Shubin invariants and Morse inequalitiesJul 01 1996It is shown that the topological phenomenon "zero in the continuous spectrum", discovered by S.P.Novikov and M.A.Shubin, can be explained in terms of a homology theory on the category of finite polyhedra with values in certain abelian category. This approach ... More
Geometry of growth: Approximation theorems for L^2 invariantsMar 21 1997In this paper we study the problem of approximation of the $L^2$-topological invariants by their finite dimensional analogues. We obtain generalizations of the theorem of L\"uck, dealing with towers of finitely sheeted normal coverings. We prove approximation ... More
Executing Arbitrary Code in the Context of the Smartcard System ServiceJan 21 2016This report summarizes our findings regarding a severe weakness in implementations of the Open Mobile API deployed on several Android devices. The vulnerability allows arbitrary code coming from a specially crafted Android application package (APK) to ... More
On an extremization problem concerning Fourier coefficientsMay 30 2015Among subsets of Euclidean space with prescribed measure, for which sets is the $L^q$ norm of the Fourier transform of the indicator function maximized? Various partial results concerning this question are established, including the existence of maximizers ... More
Electroweak Baryogenesis without the Phase TransitionSep 11 1997Radiation domination at the electroweak epoch is a simplifying assumption, but one for which there is no observational basis. Treating the expansion rate as a variable, I re-examine electroweak baryogenesis in various scenarios. At a first order phase ... More
Cosmological simulations of structure formation and the Vlasov equationMay 11 2008In cosmology numerical simulations of structure formation are now of central importance, as they are the sole instrument for providing detailed predictions of current cosmological models for a whole class of important constraining observations. These ... More
On the large-scale geometry of diffeomorphism groups of $1$-manifoldsJun 13 2016We apply the framework of Rosendal to study the large-scale geometry of the topological groups $\Diff_+^k(M^1)$, consisting of orientation-preserving $C^k$-diffeomorphisms (for $1\leq k\leq\infty$) of a compact $1$-manifold $M^1$ ($=I$ or $\mathbb{S}^1$). ... More
A Glimpse at Mathematical Diffraction TheoryMar 05 2002Mathematical diffraction theory is concerned with the analysis of the diffraction measure of a translation bounded complex measure $\omega$. It emerges as the Fourier transform of the autocorrelation measure of $\omega$. The mathematically rigorous approach ... More
Neutrinoless Double Beta Decay and Neutrino MassesJun 04 2012Neutrinoless double beta decay is a promising test for lepton number violating physics beyond the standard model of particle physics. There is a deep connection between this decay and the phenomenon of neutrino masses. In particular, we will discuss the ... More
Travelling with/against the flow. Deterministic diffusive driven systemsOct 13 2008We introduce and study a deterministic lattice model describing the motion of an infinite system of oppositely charged particles under the action of a constant electric field. As an application this model represents a traffic flow of cars moving in opposite ... More
Generalized phase transitions in finite coupled map latticesNov 23 1995We investigate generalized phase transitions of type localization - delocalization from one to several Sinai-Bowen-Ruelle invariant measures in finite networks of chaotic elements (coupled map lattices) with general graphs of connections in the limit ... More
Exclusion type spatially heterogeneous processes in continuumMay 21 2011Jun 06 2011We study deterministic discrete time exclusion type spatially heterogeneous particle processes in continuum. A typical example of this sort is a traffic flow model with obstacles: traffic lights, speed bumps, spatially varying local velocities etc. Ergodic ... More
Fermions in energon fieldOct 28 2014Dec 08 2014The behavior of fermions in the gauge field created by the energon, a recently found classical solution of the non-Abelian gauge theory, is considered. The spectrum of fermions is evaluated explicitly for the case when parameters governing the energon ... More
Simple look at supersymmetric N=2 gauge theory with arbitrary gauge groupOct 24 2011A new discrete symmetry is shown to govern and simplify low-energy properties of the supersymmetric N=2 gauge theory with an arbitrary gauge group. Each element of the related symmetry group S_r, r being the rank of the gauge group, represents a permutation ... More
Thermalization and isotropization in heavy-ion collisionsDec 09 2013I review our current understanding of the processes driving the thermalization and isotropization of the quark gluon plasma (QGP) created in ultrarelativistic heavy ion collisions (URHICs). I begin by discussing the phenomenological evidence in favor ... More
The chromo-Weibel instabilityNov 28 2006Dec 04 2006I discuss the physics of non-Abelian plasmas which are locally anisotropic in momentum space. Such momentum-space anisotropies are generated by the rapid longitudinal expansion of the matter created in the first 1 fm/c of an ultrarelativistic heavy ion ... More
Thermalization and plasma instabilitiesAug 15 2006I review recent analytical and numerical advances in the study of non-equilibrium quark-gluon plasma physics. I concentrate on studies of the dynamics of plasmas which are locally anisotropic in momentum space. In contrast to locally isotropic plasmas ... More
Hard-loop dynamics of non-abelian plasma instabilitiesSep 26 2005I discuss recent advances in the understanding of non-equilibrium gauge field dynamics in plasmas which have particle distributions which are locally anisotropic in momentum space. In contrast to locally isotropic plasmas such anisotropic plasmas have ... More
Block-Transitive Designs in Affine SpacesOct 03 2009This paper deals with block-transitive $t$-$(v,k,\lambda)$ designs in affine spaces for large $t$, with a focus on the important index $\lambda=1$ case. We prove that there are no non-trivial 5-$(v,k,1)$ designs admitting a block-transitive group of automorphisms ... More
Perfect Secrecy Systems Immune to Spoofing AttacksMay 22 2012We present novel perfect secrecy systems that provide immunity to spoofing attacks under equiprobable source probability distributions. On the theoretical side, relying on an existence result for $t$-designs by Teirlinck, our construction method constructively ... More
Efficient Two-Stage Group Testing Algorithms for DNA ScreeningJun 18 2011Group testing algorithms are very useful tools for DNA library screening. Building on recent work by Levenshtein (2003) and Tonchev (2008), we construct in this paper new infinite classes of combinatorial structures, the existence of which are essential ... More
Efficient Two-Stage Group Testing Algorithms for Genetic ScreeningJun 19 2013Efficient two-stage group testing algorithms that are particularly suited for rapid and less-expensive DNA library screening and other large scale biological group testing efforts are investigated in this paper. The main focus is on novel combinatorial ... More
Computational complexity of reconstruction and isomorphism testing for designs and line graphsJun 30 2010Graphs with high symmetry or regularity are the main source for experimentally hard instances of the notoriously difficult graph isomorphism problem. In this paper, we study the computational complexity of isomorphism testing for line graphs of $t$-$(v,k,\lambda)$ ... More
Upper bound on the rate of adaptation in an asexual populationAug 01 2011Jul 23 2013We consider a model of asexually reproducing individuals. The birth and death rates of the individuals are affected by a fitness parameter. The rate of mutations that cause the fitnesses to change is proportional to the population size, N. The mutations ... More
Fermi-Dirac integrals in terms of Zeta FunctionsSep 20 2009May 06 2011This paper shows the Fermi-Dirac Integrals expressed in terms of Riemann and Hurwitz Zeta functions. This is done by defining an auxiliar function that permits rewrite the Fermi-Dirac integral in terms of simpler and known integrals resulting in the Zeta ... More
Weight zero Eisenstein cohomology of Shimura varieties via Berkovich spacesAug 08 2012This brief article gives an alternative interpretation, based on a theorem of Berkovich, of the Eisenstein classes in the cohomology of Shimura varieties, used in forthcoming work of the author with K. W. Lan, R. Taylor, and J. Thorne.
Nonequivalence of ensembles for long-range quantum spin systems in optical latticesMar 11 2010Jun 24 2010Motivated by the anisotropic long-range nature of the interactions between cold dipolar atoms or molecules in an optical lattice, we study the anisotropic quantum Heisenberg model with Curie-Weiss-type long-range interactions. Absence of a heat bath in ... More
Monte Carlo methods in statistical physics: Mathematical foundations and strategiesJun 04 2009Monte Carlo is a versatile and frequently used tool in statistical physics and beyond. Correspondingly, the number of algorithms and variants reported in the literature is vast, and an overview is not easy to achieve. In this pedagogical review, we start ... More
Recursion relations for the partition function of the two-dimensional Ising modelMay 23 2006The partition function of the two-dimensional Ising model on a square lattice with nearest-neighbour interactions and periodic boundary conditions is investigated. Kaufman [Phys. Rev. 76, 1232--1243 (1949)] gave a solution for this function consisting ... More
Dimension dependent energy thresholds for discrete breathersJan 26 2004May 28 2004Discrete breathers are time-periodic, spatially localized solutions of the equations of motion for a system of classical degrees of freedom interacting on a lattice. We study the existence of energy thresholds for discrete breathers, i.e., the question ... More
Nonequivalence of ensembles in the Curie-Weiss anisotropic quantum Heisenberg modelMay 27 2010Jul 01 2010The microcanonical entropy s(e,m) as a function of the energy e and the magnetization m is computed analytically for the anisotropic quantum Heisenberg model with Curie-Weiss-type interactions. The result shows a number of interesting properties which ... More
Noncommutative gauge theory and renormalisabilityFeb 21 2011We review two different noncommutative gauge models generalizing approaches which lead to renormalizable scalar quantum field theories. One of them implements the crucial IR damping of the gauge field propagator in the so-called ``soft breaking'' part. ... More
Fourier transforms of irregular local hypersurface measures in R^3Sep 14 2014Aug 02 2016We prove sharp estimates for Fourier transforms of local hypersurface measures in R^3 with possibly singular density functions. These estimates are for both the normal and tangential components of the Fourier transform. The densities allowed are those ... More
Hybrid Mesons from the LatticeAug 28 2003I review lattice QCD results for hybrid mesons, including a discussion of their hadronic decays.
Hadronic transitions from the latticeOct 03 2003I discuss strategies to determine hadronic decay couplings from lattice studies. As a check of the methods, I explore the decay of a vector meson to two pseudoscalar mesons with $N_f=2$ flavours of sea quark. Although we are working with quark masses ... More
The eta and eta' mesons from lattice QCDNov 28 2001Lattice QCD allows a first-principles study of QCD with the freedom to vary the number and masses of the quarks. I present results on the flavour singlet correlations (this illuminates OZI violating effects) for mesons. Concentrating on the pseudoscalar ... More
Glueballs and Hybrid MesonsSep 08 1992We discuss states in the meson spectrum which have explicit gluonic components. Glueballs (with no valence quarks) and hybrid mesons (with valence quarks) are both reviewed. We present in some detail lattice simulation results. ( to appear in proceedings ... More
The Jones polynomial of ribbon linksFeb 15 2008Jul 28 2008For every n-component ribbon link L we prove that the Jones polynomial V(L) is divisible by the polynomial V(O^n) of the trivial link. This integrality property allows us to define a generalized determinant det V(L) := [V(L)/V(O^n)]_(t=-1), for which ... More
Dynamical variational principles for strongly correlated electron systemsMar 30 2005The self-energy-functional approach (SFA) is discussed in the context of different variational principles for strongly correlated electron systems. Formal analogies between static and dynamical variational approaches, different types of approximation ... More
Systematics of approximations constructed from dynamical variational principlesNov 30 2005The systematics of different approximations within the self-energy-functional theory (SFT) is discussed for fermionic lattice models with local interactions. In the context of the SFT, an approximation is essentially given by specifying a reference system ... More
Non-perturbative construction of the Luttinger-Ward functionalJun 28 2004For a system of correlated electrons, the Luttinger-Ward functional provides a link between static thermodynamic quantities on the one hand and single-particle excitations on the other. The functional is useful to derive several general properties of ... More
C- and O-Rich Miras and Galactic StructureSep 12 2006This paper summarizes the conclusions of an extensive investigation of variable carbon AGB stars in our Galaxy. The zero-point of the period-M(bol) relation for Galactic C-Miras is found to be close to that in the LMC. The mean age of Galactic C-Miras ... More
SALT and RR Lyrae variables: Our Galaxy, The Magellanic Clouds and the Local GroupMay 03 2004A review is given of the possibilities for the study of the kinematics and metallicities of the old populations in galaxies of the Local Group using SALT/PFIS observations of RR Lyrae variables.
Cepheids as Distance Indicators: Some Current ProblemsOct 16 2001A general review is given of the calibration of the Cepheid distance scale, with particular reference to its use in the determination of H0. Emphasis is placed on the advantage of using a galactic calibration of the Cepheid scale, rather than relying ... More
Discontinuous Jamming Transitions in Soft MaterialsJan 16 2008Many systems in nature exhibit transitions between fluid-like states and solid-like states, or "jamming transitions". There is a strong theoretical foundation for understanding equilibrium phase transitions that involve solidification, or jamming. Other ... More
Quark masses, the Dashen phase, and gauge field topologyJun 05 2013Oct 17 2013The CP violating Dashen phase in QCD is predicted by chiral perturbation theory to occur when the up-down quark mass difference becomes sufficiently large at fixed down-quark mass. Before reaching this phase, all physical hadronic masses and scattering ... More
Anomalies and discrete chiral symmetriesSep 28 2009Oct 06 2009The quantum anomaly that breaks the U(1) axial symmetry of massless multi-flavored QCD leaves behind a discrete flavor-singlet chiral invariance. With massive quarks, this residual symmetry has a close connection with the strong CP-violating parameter ... More
Hidden symmetries in two dimensional field theoryAug 16 2005Jan 31 2006The bosonization process elegantly shows the equivalence of massless scalar and fermion fields in two space-time dimensions. However, with multiple fermions the technique often obscures global symmetries. Witten's non-Abelian bosonization makes these ... More
Isospin breaking and the chiral condensateAug 13 2005With two degenerate quarks, the chiral condensate exhibits a jump as the quark masses pass through zero. I discuss how this single transition splits into two Ising like transitions when the quarks are made non-degenerate. The order parameter is the expectation ... More
Transiting topological sectors with the overlapAug 16 2002The overlap operator provides an elegant definition for the winding number of lattice gauge field configurations. Only for a set of configurations of measure zero is this procedure undefined. Without restrictions on the lattice fields, however, the space ... More
Lattice gauge theory: A retrospectiveOct 26 2000I discuss some of the historical circumstances that drove us to use the lattice as a non-perturbative regulator. This approach has had immense success, convincingly demonstrating quark confinement and obtaining crucial properties of the strong interactions ... More