Results for "Stephen Ridgway"

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Astro2020: Unlocking the Secrets of Late-Stage Stellar Evolution and Mass Loss through Radio Wavelength ImagingMar 13 2019During the late phases of evolution, low-to-intermediate mass stars like our Sun undergo periods of extensive mass loss, returning up to 80% of their initial mass to the interstellar medium. This mass loss profoundly affects the stellar evolutionary history, ... More
High Angular Resolution Astrophysics: Resolving Stellar Surface FeaturesMar 11 2019We are now in an era where we can image details on the surfaces of stars. When resolving stellar surfaces, we see that every surface is uniquely complicated. Each imaged star provides insight into not only the stellar surface structures, but also the ... More
The close circumstellar environment of Betelgeuse - Adaptive optics spectro-imaging in the near-IR with VLT/NACOJul 10 2009Context: Betelgeuse is one the largest stars in the sky in terms of angular diameter. Structures on the stellar photosphere have been detected in the visible and near-infrared as well as a compact molecular environment called the MOLsphere. Mid-infrared ... More
Properties of the CO and H$_2$O MOLsphere of the red supergiant Betelgeuse from VLTI/AMBER observationsAug 13 2014Oct 02 2014Context. Betelgeuse is the closest red supergiant (RSG); therefore, it is well suited for studying the complex processes in its atmosphere that lead to the chemical enrichment of the interstellar medium. Aims. We intend to investigate the shape and composition ... More
The close circumstellar environment of Betelgeuse - II. Diffraction-limited spectro-imaging from 7.76 to 19.50 microns with VLT/VISIRJun 24 2011Context: Mass-loss occurring in red supergiants (RSGs) is a major contributor to the enrichment of the interstellar medium in dust and molecules. The physical mechanism of this mass loss is however relatively poorly known. Betelgeuse is the nearest RSG, ... More
The Variable Sky of Deep Synoptic SurveysSep 10 2014Dec 03 2014The discovery of variable and transient sources is an essential product of synoptic surveys. The alert stream will require filtering for personalized criteria -- a process managed by a functionality commonly described as a Broker. In order to understand ... More
Mapping the Interstellar Reddening and Extinction towards Baade's Window Using Minimum Light Colors of ab-type RR Lyrae Stars. Revelations from the De-reddened Color-Magnitude DiagramsFeb 14 2019We have obtained repeated images of 6 fields towards the Galactic bulge in 5 passbands (u, g, r, i, z) with the DECam imager on the Blanco 4m telescope at CTIO. From over 1.6 billion individual photometric measurements in the field centered on Baade's ... More
Precision Analysis of Evolved StarsMar 12 2019Evolved stars dominate galactic spectra, enrich the galactic medium, expand to change their planetary systems, eject winds of a complex nature, produce spectacular nebulae and illuminate them, and transfer material between binary companions. While doing ... More
Exoplanets imaging with a Phase-Induced Amplitude Apodization Coronagraph - I. PrincipleDec 08 2004Using 2 aspheric mirrors, it is possible to apodize a telescope beam without losing light or angular resolution: the output beam is produced by ``remapping'' the entrance beam to produce the desired light intensity distribution in a new pupil. We present ... More
Computation of Gaussian orthant probabilities in high dimensionNov 05 2014Nov 25 2014We study the computation of Gaussian orthant probabilities, i.e. the probability that a Gaussian falls inside a quadrant. The Geweke-Hajivassiliou-Keane (GHK) algorithm [Genz, 1992; Geweke, 1991; Hajivassiliou et al., 1996; Keane, 1993], is currently ... More
The Search for Stellar Companions to Exoplanet Host Stars Using the CHARA ArrayMar 28 2008Most exoplanets have been discovered via radial velocity studies, which are inherently insensitive to orbital inclination. Interferometric observations will show evidence of a stellar companion if it sufficiently bright, regardless of the inclination. ... More
Active Asteroid P/2017 S5 (ATLAS)Nov 30 2018Observations of active asteroid P/2017 S5 when near perihelion reveal the ejection of large (0.1 to 10 mm) particles at 0.2 to 2 m/s speeds, with estimated mass-loss rates of a few kg/s. The protracted nature of the mass loss (continuous over 150 days) ... More
Eleven Exoplanet Host Star Angular Diameters from the CHARA ArrayJun 15 2009We directly measured the angular diameters for 11 exoplanet host stars using Georgia State University's CHARA Array interferometer and calculated their linear radii and effective temperatures. The sample tends towards evolving or evolved stars and includes ... More
The molecular and dusty composition of Betelgeuse's inner circumstellar environmentSep 04 2007The study of the atmosphere of red supergiant stars in general and of Betelgeuse (alpha Orionis) in particular is of prime importance to understand dust formation and how mass is lost to the interstellar medium in evolved massive stars. A molecular shell, ... More
An edge-on translucent dust disk around the nearest AGB star L2 Puppis - VLT/NACO spectro-imaging from 1.04 to 4.05 microns and VLTI interferometryApr 11 2014As the nearest known AGB star (d=64pc) and one of the brightest (mK-2), L2 Pup is a particularly interesting benchmark object to monitor the final stages of stellar evolution. We report new lucky imaging observations of this star with the VLT/NACO adaptive ... More
4D, N=1 Supergravity GenomicsDec 13 2012Jul 24 2013The off-shell representation theory of 4D, $\mathcal{N}=1$ supermultiplets can be categorized in terms of distinct irreducible graphical representations called adinkras as part of a larger effort we call supersymmetry `genomics.' Recent evidence has emerged ... More
Discovering and Characterizing the Planetary Systems of Nearby Stars: The scientific need for medium aperture space coronagraph observationsFeb 24 2009Significant advances in the discovery and characterization of the planetary systems of nearby stars can be accomplished with a moderate aperture high performance coronagraphic space mission that could be started in the next decade. Its observations would ... More
First Data Release of the All-sky NOAO Source CatalogJan 05 2018Jul 26 2018Most of the sky has been imaged with NOAO's telescopes from both hemispheres. While the large majority of these data were obtained for PI-led projects and almost all of the images are publicly available, only a small fraction have been released to the ... More
Cepheid distances from the SpectroPhoto-Interferometry of Pulsating Stars (SPIPS) - Application to the prototypes delta Cep and eta AqlOct 07 2015The parallax of pulsation, and its implementations such as the Baade-Wesselink method and the infrared surface bright- ness technique, is an elegant method to determine distances of pulsating stars in a quasi-geometrical way. However, these classical ... More
High-Resolution Infrared Spectroscopy of the Brown Dwarf Epsilon Indi BaNov 10 2003We report on the analysis of high-resolution infrared spectra of the newly discovered brown dwarf Epsilon Indi Ba. This is the closest known brown dwarf to the solar system, with a distance of 3.626 pc. Spectra covering the ranges of 2.308-2.317 microns ... More
Ruling Out Possible Secondary Stars to Exoplanet Host Stars Using the CHARA ArrayMay 17 2010Of the over 450 exoplanets known to date, more than 420 of them have been discovered using radial velocity studies, a method that tells nothing about the inclination of the planet's orbit. Because it is more likely that the companion is a planetary-mass ... More
Quantifying Stellar Mass Loss with High Angular Resolution ImagingFeb 17 2009Mass is constantly being recycled in the universe. One of the most powerful recycling paths is via stellar mass-loss. All stars exhibit mass loss with rates ranging from ~10(-14) to 10(-4) M(sun) yr-1, depending on spectral type, luminosity class, rotation ... More
CHARA Array Measurements of the Angular Diameters of Exoplanet Host StarsMar 10 2008We have measured the angular diameters for a sample of 24 exoplanet host stars using Georgia State University's CHARA Array interferometer. We use these improved angular diameters together with Hipparcos parallax measurements to derive linear radii and ... More
The Angular Diameter and Effective Temperature of the Lithium-Rich K Giant HD 148293 from the CHARA ArrayMar 14 2011We measured the angular diameter of the lithium-rich K giant star HD 148293 using Georgia State University's Center for High Angular Resolution Astronomy (CHARA) Array interferometer. We used our measurement to calculate the star's effective temperature, ... More
Hosts and Alignment Effect in 0.5 < z < 1 radio sourcesSep 11 1998R- and I- band images with good seeing at the NOT of the hosts of a sample of 7C radio galaxies at z ~ 0.7 (with mean radio flux 20 times fainter than the 3C sample) show some evidence of radio-optical alignment. A quantitative analysis of the alignment ... More
Concentration of tempered posteriors and of their variational approximationsJun 28 2017Jun 07 2018While Bayesian methods are extremely popular in statistics and machine learning, their application to massive datasets is often challenging, when possible at all. Indeed, the classical MCMC algorithms are prohibitively slow when both the model dimension ... More
Fundamental Parameters of the Exoplanet Host K Giant Star iota Draconis from the CHARA ArraySep 22 2011We measured the angular diameter of the exoplanet host star iota Dra with Georgia State University's Center for High Angular Resolution Astronomy (CHARA) Array interferometer, and, using the star's parallax and photometry from the literature, calculated ... More
Notes on normed algebras, 3Mar 22 2004In these notes we briefly consider various situations related to infinite commutative semigroups, connected to convolutions and Fourier transforms.
Elements of harmonic analysis, 5Mar 16 2004These notes are concerned with the Schwartz class of rapidly decreasing smooth functions on R^n, Fourier transforms, etc.
Elements of harmonic analysisFeb 12 2004These informal notes briefly discuss some basic topics in harmonic analysis along the lines of convolutions and Fourier transforms.
Some remarks about Cauchy integralsAug 08 2003Oct 17 2003This article describes some aspects of Cauchy integrals and related geometry of sets and measures in Euclidean spaces, etc.
Some remarks about Clifford analysis and fractal setsSep 14 2007Sep 15 2007Although Clifford analysis is like complex analysis in many ways, there are obvious differences related to noncommutativity, and a few aspects of this are considered here.
Potpourri, 4Sep 29 2004These notes, connected to a "potpourri" topics course currently underway, are concerned with some interrelated themes of polynomials, functions on the unit circle or interval, and norms.
Potpourri, 3Sep 19 2004These notes are connected to a "potpourri" topics class and deal with some special cases of norms of various objects which arise in classical analysis.
Some topics in complex and harmonic analysisMar 11 2004These notes briefly discuss Fourier transforms of finite measures and extensions of Fourier integrals to points in complex domains.
Some remarks about curves in metric spacesMar 09 2004Here we consider a few topics related to Lipschitz classes for functions and curves in metric spaces.
Some notes about matrices, 4Sep 06 2003In these notes we focus a bit on the complex case for some families of matrices and equivalences between them.
A brief introduction to p-adic numbersJan 05 2003Jan 07 2003In this short survey we look at a few basic features of p-adic numbers, somewhat with the point of view of a classical analyst. In particular, with p-adic numbers one has arithmetic operations and a norm, just as for real or complex numbers.
Complementary self-similarityOct 08 2007A few aspects of self-similarity related to complementary components of closed subsets of R^n are briefly discussed.
A few remarks about linear operators and disconnected open sets in the planeOct 01 2007Some aspects of analysis on disconnected open subsets of the plane with connected fractal boundary are discussed.
Quantum measurements need not conserve energy: relation to the Wigner-Araki-Yanase theoremOct 14 2016Oct 18 2016The paper focuses on the fact that quantum projective measurements do not necessarily conserve energy. On the other hand the Wigner-Araki-Yanase (WAY) theorem states that assuming a "standard" von Neumann measurement model and "additivity" of the total ... More
The Effects of Latent Infection on the Dynamics of HIVDec 12 2013One way in which the human immunodeficiency virus (HIV-1) replicates within a host is by infecting activated CD4+ T-cells, which then produce additional copies of the virus. Even with the introduction of antiretroviral drug therapy, which has been very ... More
Multi-wavelength probes of distant lensed galaxiesDec 01 2011I summarise recent results on multi-wavelength properties of distant lensed galaxies, with a particular focus on Herschel. Submm surveys have already resulted in a breakthrough discovery of an extremely efficient selection technique for strong gravitational ... More
Trapezoid Order ClassificationDec 11 1996We show the nonequivalence of combinations of several natural geometric restrictions on trapezoid representations of trapezoid orders. Each of the properties unit parallelogram, unit trapezoid and proper parallelogram, unit trapezoid and parallelogram, ... More
Problems with the Quenched Approximation in the Chiral LimitNov 02 1992In the quenched approximation, loops of the light singlet meson (the $\eta'$) give rise to a type of chiral logarithm absent in full QCD. These logarithms are singular in the chiral limit throwing doubt upon the utility of the quenched approximation. ... More
Quantum Exchangeable Sequences of AlgebrasDec 17 2008May 14 2009We extend the notion of quantum exchangeability, introduced by K\"ostler and Speicher in arXiv:0807.0677, to sequences (\rho_1,\rho_2,...c) of homomorphisms from an algebra C into a noncommutative probability space (A,\phi), and prove a free de Finetti ... More
Analytic Subordination for Free CompressionMar 31 2008Apr 02 2008We extend the free difference quotient coalgebra approach to analytic subordination to the case of a free compression in free probability.
Inflation from a Non-Local Theory of GravityAug 19 2009This paper studies the inflationary dynamics of a Non-Local Theory of gravity. This theory, based around derivatives of the Ricci Scalar in the Einstein-Hilbert action, was previously found to be Ghost free, and to give rise to a bouncing cosmology. Perturbation ... More
The Distance to the M31 Globular Cluster SystemFeb 07 1998The distance to the centroid of the M31 globular cluster system is determined by fitting theoretical isochrones to the observed red-giant branches of fourteen globular clusters in M31. The mean true distance modulus of the M31 globular clusters is found ... More
Morita contexts as lax functorsSep 20 2012Apr 08 2013Monads are well known to be equivalent to lax functors out of the terminal category. Morita contexts are here shown to be lax functors out of the chaotic category with two objects. This allows various aspects in the theory of Morita contexts to be seen ... More
Improving on the empirical covariance matrix using truncated PCA with white noise residualsJun 07 2005The empirical covariance matrix is not necessarily the best estimator for the population covariance matrix: we describe a simple method which gives better estimates in two examples. The method models the covariance matrix using truncated PCA with white ... More
Probabilistic temperature forecasting: a comparison of four spread-regression modelsOct 08 2004Spread regression is an extension of linear regression that allows for the inclusion of a predictor that contains information about the variance. It can be used to take the information from a weather forecast ensemble and produce a probabilistic prediction ... More
Use of the likelihood for measuring the skill of probabilistic forecastsAug 12 2003Jan 08 2004We define the likelihood and give a number of justifications for its use as a skill measure for probabilistic forecasts. We describe a number of different scores based on the likelihood, and briefly investigate the relationships between the likelihood, ... More
A majorization bound for the eigenvalues of some graph LaplaciansNov 07 2004It is conjectured that the Laplacian spectrum of a graph is majorized by its conjugate degree sequence. In this paper, we prove that this majorization holds for a class of graphs including trees. We also show that a generalization of this conjecture to ... More
Comments on Beckmann's Uniform ReductsJan 19 2006Jan 23 2006Arnold Beckmann defined the uniform reduct of a propositional proof system f to be the set of those bounded arithmetical formulas whose propositional translations have polynomial size f-proofs. We prove that the uniform reduct of f + Extended Frege consists ... More
Single-degenerate type Ia supernovae without hydrogen contaminationFeb 24 2011Feb 28 2011The lack of hydrogen in spectra of type Ia supernovae (SN Ia) is often seen as troublesome for single-degenerate (SD) progenitor models. We argue that, since continued accretion of angular momentum can prevent explosion of the white dwarf, it may be natural ... More
Top Quark, W-boson and Light HiggsOct 14 1997In this presentation I will concentrate on top quark physics, the W-boson mass and the possibility of discovering a light Higgs boson via associated production at the Fermilab Tevatron.
Q-Ball CondensationJun 11 2007Jul 04 2007Q-balls arise in particle theories with U(1) global symmetry. The coupling of the corresponding scalar field to fermions leads to Q-ball evaporation. In this paper we consider the oposite problem, the case where a Q-ball absorbs particles to grow. In ... More
Particle production from Q-ballsOct 06 2005Jul 04 2006Non topological solitons, Q-balls can arise in many particle theories with U(1) global symmetries. As was shown by Cohen et al. \cite{Qballscohen}, if the corresponding scalar field couples to massless fermions, large Q-balls are unstable and evaporate, ... More
A Finite Reflection Formula For A Polynomial Approximation To The Riemann Zeta FunctionOct 27 2012The Riemann zeta function can be written as the Mellin transform of the unit interval map w(x) = floor(1/x)*(-1+x*floor(1/x)+x) multiplied by s((s+1)/(s-1)). A finite-sum approximation to \zeta (s) denoted by \zeta_w(N;s) which has real roots at s=-1 ... More
Unitary representations of rational Cherednik algebras, IIJun 25 2011The goal of this paper is to classify the unitary irreducible modules in category O for the rational Cherednik algebras of type G(r,1,n). As a first step, we classify those irreducibles in O that are diagonalizable with respect to a commutative subalgebra ... More
Spatial Modelling Techniques in Microsoft ExcelJan 30 2014We begin by considering the expectations of the creators of VisiCalc, the first spreadsheet. The emphasis is on the nature of the spreadsheet grid. The grid is taken as a presentational method for showing a solution to a Sudoku puzzle. We consider methods ... More
A diagrammatic Alexander invariant of tanglesMar 25 2012We give a new construction of the one-variable Alexander polynomial of an oriented knot or link, and show that it generalizes to a vector valued invariant of oriented tangles.
Universal monopole scaling near transitions from the Coulomb phaseMar 20 2012Certain frustrated systems, including spin ice and dimer models, exhibit a Coulomb phase at low temperatures, with power-law correlations and fractionalized monopole excitations. Transitions out of this phase, at which the effective gauge theory becomes ... More
Bootstrapping the Mazur--Orlicz--König theoremDec 25 2015In this paper, we give some extensions of K\"onig's extension of the Mazur-Orlicz theorem. These extensions include generalizations of a surprising recent result of Sun Chuanfeng, and generalizations to the product of more than two spaces of the "Hahn-Banach-Lagrange" ... More
Global Existence for the Vlasov-Poisson System with Steady Spatial AsymptoticsJan 05 2010A collisionless plasma is modeled by the Vlasov-Poisson system in three space dimensions. A fixed background of positive charge - dependant upon only velocity - is assumed. The situation in which mobile negative ions balance the positive charge as x tends ... More
The Laplacian of The Integral Of The Logarithmic Derivative of the Riemann-Siegel-Hardy Z-functionNov 23 2015Mar 27 2016The integral $R(t)={\pi}^{-1}(ln{\zeta}(\frac{1}{2}+it)+i\vartheta (t))$ of the logarithmic derivative of the Hardy Z function $Z(t)=e^{i\vartheta (t)}{\zeta}(\frac{1}{2}+it)$, where $\vartheta (t)$ is the Riemann-Siegel theta function, and $\zeta (t)$ ... More
Bowling ball representations of braid groupsSep 14 2014In a remark in his seminal 1987 paper, Jones describes a way to define the Burau matrix of a positive braid using a metaphor of bowling a ball down a bowling alley with braided lanes. We extend this definition to allow multiple bowling balls to be bowled ... More
Projective Dimensions and Extensions of Modules from Titled to Cluster-Tilted AlgebrasAug 04 2016We study the module categories of a tilted algebra C and the corresponding cluster-tilted algebra B. We investigate how various properties of a C-module are affected when considered in the module category of B. We give a complete classification of the ... More
Comment on $Z'$'s and the H1 and ZEUS High $Q^2$ AnomaliesApr 22 1997We investigate the effects of extra neutral gauge bosons on the high $Q^2$ region of the $e^+p \to e^+ X$ cross section at $\sqrt{s}=300$ GeV. We found that the only models with electroweak strength coupling, typical of extended gauge theories, that give ... More
A Quillen model structure for Gray-categoriesJan 14 2010Feb 05 2010A Quillen model structure on the category Gray-Cat of Gray-categories is described, for which the weak equivalences are the triequivalences. It is shown to restrict to the full subcategory Gray-Gpd of Gray-groupoids. This is used to provide a functorial ... More
Homological representations of the Iwahori-Hecke algebraDec 28 2004Representations of the Iwahori-Hecke algebra of type A_{n-1} are equivalent to representations of the braid group B_n for which the generators satisfy a certain quadratic relation. We show how to construct such representations from the natural action ... More
On the splitting of quasilinear $p$-formsOct 29 2012Nov 01 2012We study the splitting behaviour of quasilinear $p$-forms in the spirit of the theory of nondegenerate quadratic forms over fields of characteristic different from 2 using an analogue of M. Knebusch's generic splitting tower. Several new applications ... More
Note on the construction of free monoidsFeb 14 2008Sep 15 2008We construct free monoids in a monoidal category with finite limits and countable colimits, in which tensoring on either side preserves reflexive coequalizers and colimits of countable chains.
Improvements to exact Boltzmann sampling using probabilistic divide-and-conquer and the recursive methodAug 29 2016We demonstrate an approach for exact sampling of certain discrete combinatorial distributions, which is a hybrid of exact Boltzmann sampling and the recursive method, using probabilistic divide-and-conquer (PDC). The approach specializes to exact Boltzmann ... More
A 2-categories companionFeb 19 2007This paper is a rather informal guide to some of the basic theory of 2-categories and bicategories, including notions of limit and colimit, 2-dimensional universal algebra, formal category theory, and nerves of bicategories. As is the way of these things, ... More
Maximal perimeters of polytope sections and origin-symmetryMar 05 2018Let $P\subset\mathbb{R}^n$ $(n\geq 3)$ be a convex polytope containing the origin in its interior. Let $\mbox{vol}_{n-2} \big( \mbox{relbd} ( P\cap\lbrace t\xi + \xi^\perp \rbrace ) \big)$ denote the $(n-2)$-dimensional volume of the relative boundary ... More
Unitary representations of cyclotomic rational Cherednik algebrasJun 25 2011Nov 28 2017We classify the irreducible unitary modules in category O for the rational Cherednik algebras of type G(r,1,n) and give explicit combinatorial formulas for their graded characters. More precisely, we produce a combinatorial algorithm determining, for ... More
$τ$-Tilting Finite Tilted and Cluster-Tilted AlgebrasFeb 13 2019Let B be a tilted or cluster-tilted algebra. We prove that B is $\tau$-tilting finite if and only if B is representation-finite.
Quantum Key Distribution Highly Sensitive to EavesdroppingOct 14 2009We introduce a new quantum key distribution protocol that uses d-level quantum systems to encode an alphabet with c letters. It has the property that the error rate introduced by an intercept-and-resend attack tends to one as the numbers c and d increase. ... More
Up to 100,000 reliable strong gravitational lenses in future dark energy experimentsSep 01 2014The Euclid space telescope will observe ~10^5 strong galaxy-galaxy gravitational lens events in its wide field imaging survey over around half the sky, but identifying the gravitational lenses from their observed morphologies requires solving the difficult ... More
Computer Simulations of High Energy PhysicsAug 31 2004This thesis describes the development of two independent computer programs, Herwig++ and Effective. Both of these programs are used for phenomenological predictions of high energy physics. Herwig++ is used to simulate events as measured at particle colliders. ... More
Some topics related to metrics and norms, including ultrametrics and ultranormsMar 06 2015Here we look at some geometric properties related to connectedness and topological dimension 0, especially in connection with norms on vector spaces over fields with absolute value functions, which may be non-archimedian.
A model for singularity formation in three-dimensional Euler and Navier-Stokes flowsOct 06 2012Oct 26 2012We present a formal, approximate model for singularity formation in classical fluid dynamics in three dimensions. The construction utilizes an approximation of local two-dimensionality to study an anti-parallel hairpin vortex structure with a cross-section ... More
Making use of the information in ensemble weather forecasts: comparing the end to end and full statistical modelling approachesSep 20 2004We discuss how ensemble weather forecasts can be used, and highlight the advantages and disadvantages of two particular methods.
The problem with the Brier scoreJan 10 2004The Brier score is frequently used by meteorologists to measure the skill of binary probabilistic forecasts. We show, however, that in simple idealised cases it gives counterintuitive results. We advocate the use of an alternative measure that has a more ... More
Moment based methods for ensemble assessment and calibrationSep 08 2003We describe various moment-based ensemble interpretation models for the construction of probabilistic temperature forecasts from ensembles. We apply the methods to one year of medium range ensemble forecasts and perform in and out of sample testing. Our ... More
Interactions of Q-balls and matterApr 17 2006Apr 19 2006We know from previous work \cite{clark} that non topological solitons, Q balls, evaporate into fermions. All the constructions we used to find evaporation rate were dased on the fact that no fermions would move towards the Q ball. All these constructions ... More
Refined Simulations of the Reaction Front for Diffusion-Limited Two-Species Annihilation in One DimensionOct 18 1994Oct 20 1994Extensive simulations are performed of the diffusion-limited reaction A$+$B$\to 0$ in one dimension, with initially separated reagents. The reaction rate profile, and the probability distributions of the separation and midpoint of the nearest-neighbour ... More
The Burau representation is not faithful for n = 5Apr 20 1999Nov 30 1999The Burau representation is a natural action of the braid group B_n on the free Z[t,t^{-1}]-module of rank n-1. It is a longstanding open problem to determine for which values of n this representation is faithful. It is known to be faithful for n=3. Moody ... More
The Curvature of a Single Operator on a Hilbert SpaceJun 29 2000This note studies Arveson's curvature invariant for d-contractions specialized to the case d=1 of a single contraction operator on a Hilbert space. It establishes a formula which gives an easy-to-understand meaning for the curvature of a single contraction. ... More
Schur-Weyl duality in positive characteristicOct 19 2006Aug 28 2008Complete proofs of Schur-Weyl duality in positive characteristic are scarce in the literature. The purpose of this survey is to write out the details of such a proof, deriving the result in positive characteristic from the classical result in characteristic ... More
On the Interpretation of Spreadsheets within their EnvironmentSep 16 2012A demonstration in MS Excel to show how users can connect their spreadsheet models to the external environment that the model represents. We employ indexes to generate a list of relevant evidence that is hyperlinked to the context in which the evidence ... More
Gauge Invariant Uniqueness Theorem for Corners of k-graphsJun 29 2005For a finitely aligned k-graph $\Lambda$ with X a set of vertices in $\Lambda$ we define a universal C*-algebra called $C^*(\Lambda,X)$ generated by partial isometries. We show that $C^*(\Lambda,X)$ is isomorphic to the corner $P_XC^*(\Lambda)P_X$, where ... More
Sinkhorn Divergence of Topological Signature Estimates for Time Series ClassificationFeb 14 2019Distinguishing between classes of time series sampled from dynamic systems is a common challenge in systems and control engineering, for example in the context of health monitoring, fault detection, and quality control. The challenge is increased when ... More
Hyperbolicity and near hyperbolicity of quadratic forms over function fields of quadricsSep 22 2016Let $q$ and $p$ be anisotropic quadratic forms of dimension $\geq 2$ over a field $F$ of characteristic $\neq 2$, and let $i$ be the unique non-negative integer such that $2^i < \mathrm{dim}(p) \leq 2^{i+1}$. We show that if $q$ becomes hyperbolic over ... More
τ-Rigid Modules from Tilted to Cluster-Tilted AlgebrasAug 08 2016We study the module categories of a tilted algebra C and the corresponding cluster-tilted algebra B. In particular, we study which \tau-rigid C-modules are also \tau-rigid B-modules. In the special case where the C-module M is an indecomposable \tau-rigid ... More
Top Quark Physics at a Polarized Muon ColliderFeb 09 1998Top quark pair production is presented at a polarized Muon Collider above the threshold region. The off-diagonal spin basis is the natural basis for this discussion as the top quark pairs are produced in an essentially unique spin configuration for 100% ... More
Top Quark Production DynamicsNov 30 1995I review standard top quark production at the Fermilab Tevatron. The current theoretical understanding of the total cross section and many partial differential cross sections is presented. Studies on the effects of extra gluon radiation on the top quark ... More
What is $Δm^2_{ee}$ ?Jan 27 2016The current short baseline reactor experiments, Daya Bay and RENO (Double Chooz) have measured (or are capable of measuring) an effective $\Delta m^2$ associated with the atmospheric oscillation scale of 0.5 km/MeV in electron anti-neutrino disappearance. ... More