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
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
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
DarkHistory: A code package for calculating modified cosmic ionization and thermal histories with dark matter and other exotic energy injectionsApr 19 2019We present a new public Python package, DarkHistory, for computing the effects of dark matter annihilation and decay on the temperature and ionization history of the early universe. DarkHistory simultaneously solves for the evolution of the free electron ... 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
Optimizing the Evaluation of Finite Element MatricesMay 14 2012Assembling stiffness matrices represents a significant cost in many finite element computations. We address the question of optimizing the evaluation of these matrices. By finding redundant computations, we are able to significantly reduce the cost of ... 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
Exploring Active Supermassive Black Holes at 100 Micro-arcsecond ResolutionMar 22 2019Super-high spatial resolution observations in the infrared are now enabling major advances in our understanding of supermassive black hole systems at the centers of galaxies. Infrared interferometry, reaching resolutions of milliarcseconds to sub-milliarcseconds, ... 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
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
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
The Planet Formation ImagerJul 30 2018The Planet Formation Imager (PFI, www.planetformationimager.org) is a next-generation infrared interferometer array with the primary goal of imaging the active phases of planet formation in nearby star forming regions. PFI will be sensitive to warm dust ... 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
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
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
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
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
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
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
Points with finite orbits for trace mapsNov 08 2016We study an action of ${\rm Aut}(F_n)$ on $\mathbb{R}^{2^n-1}$ by trace maps, defined using the traces of $n$-tuples of matrices in $\mathrm{SL}(2,\mathbb{C})$ having real traces. We determine the finite orbits for this action. These orbits essentially ... More
Quantum Hamiltonian reduction of W-algebras and category OOct 26 2015We define a quantum version of Hamiltonian reduction by stages, producing a construction in type A for a quantum Hamiltonian reduction from the W-algebra $U(\mathfrak{g},e_1)$ to an algebra conjecturally isomorphic to $U(\mathfrak{g},e_2)$, whenever $e_2 ... More
Observation of Top Quark Production in the Forward Region at LHCbFeb 29 2016Forward top production is observed, in the ${\mu}+b$ final state, with the 3 fb$^{-1}$ Run I dataset collected by the LHCb detector. The combined cross-section for $t\bar{t}$ and single top production at $\sqrt{s}=7$ TeV and $\sqrt{s}=8$ TeV is measured, ... More
The Artin-Springer Theorem for quadratic forms over semi-local rings with finite residue fieldsFeb 24 2016Feb 29 2016Let $R$ be a commutative and unital semi-local ring in which 2 is invertible. In this note, we show that anisotropic quadratic spaces over $R$ remain anisotropic after base change to any odd-degree finite \'{e}tale extension of $R$. This generalization ... More
Charmed baryons from LHCbSep 18 2015The vast amount of $c\overline{c}$ production that can be recorded by the LHCb detector makes it an ideal environment to study the hadronic production of charmed baryons, along with the properties of their decays. We briefly describe the LHCb experiment ... 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
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
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
Top Quark Physics: OverviewDec 23 1997In this presentation I will primarily focus on top quark physics but I will include a discussion of the W-boson mass and the possibility of discovering a light Higgs boson via associated production at the Tevatron.
Practical Cosmology with LensesDec 04 2013Nov 04 2014Surveys with submillimetre telescopes are revealing large numbers of gravitationally lensed high-redshift sources. I describe how, in practice, these lensed systems could be simultaneously used to estimate the values of cosmological parameters, test models ... 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 geometric construction for fractal sets and related linear operatorsOct 12 2007A way to add an extra dimension is briefly discussed.
Some aspects of calculus on non-smooth setsSep 17 2007Sep 20 2007Sets in R^n in which every pair of elements x, y can be connected by a path in the set of length bounded by a constant multiple of the distance between x and y are considered.
A few remarks about operator theory, topology, and analysis on metric spacesMar 13 2007Sep 02 2007Some basic facts about Fredholm indices are briefly reviewed, often used in connection with Toeplitz and pseudodifferential operators, and which may be relevant for operators associated to fractals.
Notes on Lie algebras and Lie groupsDec 24 2004These notes deal with a few aspects of Lie algebras and Lie groups, including some matters related to exponentiation.
Potpourri, 10Nov 09 2004These notes, associated with a topics course, are largely concerned with Hausdorff measures and a class of metric spaces which behave like Cantor sets.
Potpourri, 9Oct 30 2004These notes, associated with a topics course, are concerned with Hausdorff measures and Lipschitz functions on metric spaces.
Elements of harmonic analysis, 3Feb 20 2004These notes briefly discuss basic notions concerning locally compact abelian topological groups and Fourier transforms of functions on them.
Some notes about matrices, 2Sep 02 2003Here we briefly discuss lattices in Euclidean spaces and spaces of lattices, which are basic objects that can be described in terms of matrices and are important settings in classical analysis.
Notes on topological vector spacesApr 02 2003Apr 13 2003These are some informal notes concerning topological vector spaces, with a brief overview of background material and basic notions, and emphasis on examples related to classical analysis.
p-Adic Heisenberg Cantor sets, 2Oct 01 2011Oct 18 2011In these informal notes, we continue to explore p-adic versions of Heisenberg groups and some of their variants, including the structure of the corresponding Cantor sets.
p-Adic Heisenberg Cantor setsMar 27 2011These informal notes deal with p-adic versions of Heisenberg groups and related matters.
Notes on groups and representationsAug 19 2004These informal notes concern some basic themes of harmonic analysis related to representations of groups.
Some topics in complex and harmonic analysis, 5Apr 07 2004These notes deal with a few properties of convolutions in the role of approximations to the identity.
Some remarks about metric spacesAug 08 2003Nov 29 2003The first section of this modest survey reviews some basic notions and describes some families of examples, and the second section briefly indicates some general aspects of analysis on metric spaces. The remaining three sections are concerned with some ... More
Where the Buffalo Roam: Infinite Processes and Infinite ComplexityFeb 25 2003These informal notes, initially prepared a few years ago, look at various questions related to infinite processes in several parts of mathematics, with emphasis on examples.
Some remarks about homeomorphisms, "energy", and so onNov 07 2002Jan 14 2003This paper briefly discusses some questions with analytical and topological aspects, with hopefully some useful references on both sides.
Some topics concerning analysis on metric spaces and semigroups of operatorsNov 09 2002This is a brief survey which reviews some traditional themes in harmonic analysis and some more recent areas of activity, connected to "analysis on fractals" in particular.
Report on the trimestre "Heat kernels, random walks, and analysis on manifolds and graphs" at the Centre Emile Borel (Institut Henri Poincare, Spring, 2002)Nov 09 2002Nov 13 2002This report tries to give a brief overview of a number of the mathematical activities during the trimestre mentioned in the title.
Happy fractals and some aspects of analysis on metric spacesNov 07 2002Mar 20 2003By a "happy fractal" we mean a metric space with bounded geometry in the sense of a doubling condition and a lot of paths of finite length, so that any pair of points can be connected by a path whose length is less than or equal to a constant times the ... More
Some topics concerning harmonic analysis on metric spacesNov 06 2002In this brief survey we give an introduction to some aspects of "atoms" on metric spaces and their connection with linear operators.
What are Physical States?Mar 22 2019The concept of the physical state of a system is ubiquitous in physics but is usually presented in terms of specific cases. For example, the state of a point particle of mass m is completely characterized by its position and momentum. There is a tendency ... More
The metatheory of first-order logic: a contribution to a defence of Principia MathematicaMar 23 2010Nov 28 2010This paper presents an account of the first-order logic of Principia Mathematica and preliminary evidence that the system is superior to currently accepted classical rivals. A widely accepted view that Whitehead and Russell's presentation of logic in ... More
Polar subspaces and automatic maximalityDec 11 2012Mar 28 2013This paper is about certain linear subspaces of Banach SN spaces (that is to say Banach spaces which have a symmetric nonexpansive linear map into their dual spaces). We apply our results to monotone linear subspaces of the product of a Banach space and ... More
A Brezis-Browder theorem for SSDB spacesApr 24 2010Sep 26 2010In this paper, we show how the Brezis-Browder theorem for maximally monotone multifunctions with a linear graph on a reflexive Banach space, and a consequence of it due to Yao, can be generalized to SSDB spaces.
Banach SSD spaces and classes of monotone setsAug 04 2009Jul 05 2010In this paper, we unify the theory of SSD spaces and the theory of strongly representable sets, and we apply our results to the theory of the various classes of maximally monotone sets. In particular, we prove that type (ED), dense type, type (D), type ... More
Gossez's skew linear map and its pathological maximally monotone multifunctionsJul 16 2018Jan 15 2019In this note, we give a generalization of Gossez's example of a maximally monotone multifunction such that the closure of its range is not convex, using more elementary techniques than in Gossez's original papers. We also discuss some new properties of ... More
Quasidensity: a survey and some examplesNov 16 2017Jul 24 2018In three previous papers, we discussed quasidense multifunctions from a Banach space into its dual, or, equivalently, quasidense subsets of the product of a Banach space and its dual. In this paper, we survey (without proofs) some of the main results ... More
String-Like Lagrangians from a Generalized GeometryOct 03 2007Aug 19 2009This note will use Hitchin's generalized geometry and a model of axionic gravity developed by Warren Siegel in the mid-nineties to show that the construction of Lagrangians based on the inner product arising from the pairing of a vector and its dual can ... 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
Link Patterns and the Catalan TreeMay 21 2013We demonstrate that a natural construction based on the two notions of insertion of a strand and finding the preimages of Temperley-Lieb algebra generators give an inductive means to generate all link patterns of a given number of strands. It is shown ... More
Non-tangential limits for analytic Lipschitz functionsNov 28 2018Let $U$ be a bounded open subset of the complex plane. Let $0<\alpha<1$ and let $A_{\alpha}(U)$ denote the space of functions that satisfy a Lipschitz condition with exponent $\alpha$ on the complex plane, are analytic on $U$ and are such that for each ... More
Exact sampling algorithms for Latin squares and Sudoku matrices via probabilistic divide-and-conquerFeb 01 2015Sep 08 2016We provide several algorithms for the exact, uniform random sampling of Latin squares and Sudoku matrices via probabilistic divide-and-conquer (PDC). Our approach divides the sample space into smaller pieces, samples each separately, and combines them ... More
The Lawrence-Krammer representationApr 04 2002The Lawrence-Krammer representation of the braid groups recently came to prominence when it was shown to be faithful by myself and Krammer. It is an action of the braid group on a certain homology module $H_2(\tilde{C})$ over the ring of Laurent polynomials ... 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
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
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
Milnor $K$-groups and function fields of hypersurfaces in positive characteristicFeb 29 2012Nov 18 2013Let $X$ be an integral affine or projective hypersurface over a field $F$ of characteristic $p>0$, and let $F(X)$ denote its function field. In a recent article, Dolphin and Hoffmann obtained an explicit description of the kernel of the natural restriction ... More
Alternating paths of fully packed loops and inversion numberFeb 12 2012Jan 05 2013We consider the set of alternating paths on a fixed fully packed loop of size n. This set is in bijection with the set of fully packed loops of size n. Furthermore, for a special choice of fully packed loop, we demonstrate that the set of alternating ... More
On the planar algebra of Ocneanu's asymptotic inclusionMay 12 2012In recent joint work with V. Jones and D. Shlyakhtenko, we have given a diagrammatic description of Popa's symmetric enveloping inclusion for planar algebra subfactors. In this paper we give a diagrammatic construction of the associated Jones tower, in ... More
Skein theory for the ADE planar algebrasMar 01 2009We give generators and relations for the planar algebras corresponding to $ADE$ subfactors. We also give a basis and an algorithm to express an arbitrary diagram as a linear combination of these basis diagrams.
Representations of Surface Groups and Right-Angled Artin Groups in Higher RankJan 17 2007Jan 19 2007We give very flexible, concrete constructions of discrete and faithful epresentations of right-angled Artin groups into higher-rank Lie groups. Using the geometry of the associated symmetric spaces and the combinatorics of the groups, we find a general ... More
Supersymmetric Tensor Hierarchies from Superspace CohomologyJul 05 2016Feb 13 2017In this set of lectures we give a pedagogical introduction to the way in which the nilpotency of a super-de Rham operator can be exploited for the construction of gauge theories in superspace. We begin with a discussion of how the super-geometric closure ... More
Hyperbolicity and near hyperbolicity of quadratic forms over function fields of quadricsSep 22 2016Oct 09 2017Let $p$ and $q$ be anisotropic quadratic forms over a field $F$ of characteristic $\neq 2$, let $s$ be the unique non-negative integer such that $2^s < \mathrm{dim}(p) \leq 2^{s+1}$, and let $k$ denote the dimension of the anisotropic part of $q$ after ... More
Explicit Solutions of the One-dimensional Vlasov-Poisson System with Infinite Mass and EnergyFeb 26 2010A collisionless plasma is modeled by the Vlasov-Poisson system in one-dimension. A fixed background of positive charge, dependent only upon velocity, is assumed and the situation in which the mobile negative ions balance the positive charge as x tends ... More
Leave Pima Indians alone: binary regression as a benchmark for Bayesian computationJun 29 2015Abstract. Whenever a new approach to perform Bayesian computation is introduced, a common practice is to showcase this approach on a binary regression model and datasets of moderate size. This paper discusses to which extent this practice is sound. It ... More
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
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
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