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Results for "David Piorunek"

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Discovery of new stable and high-temperature Ti-Ta-X shape memory alloys from first principles calculationsMay 14 2019In conventional Ti-Ta shape memory alloys (SMAs), high (>100{\deg}C) transformation temperatures cannot be achieved without compromising the stability of the shape memory effect. A solution to this problem is the addition of other elements to form Ti-Ta-X ... More
The RASNIK Real-Time Relative Alignment Monitor for the CDF Inner Tracking DetectorsDec 10 2002We describe the design and operation of the RASNIK optical relative alignment system designed for and installed on the CDF inner tracking detectors. The system provides low-cost minute-by-minute alignment monitoring with submicron precision. To reduce ... More
Results for the LISA Phase Measurement System ProjectNov 01 2004Jan 11 2005This article presents some of the more topical results of a study into the LISA phase measurement system. This system is responsible for measuring the phase of the heterodyne signal caused by the interference of the laser beams between the local and far ... More
Site Disordered Spin Systems in the Gaussian Variational ApproximationJun 06 1996Dec 16 1996We define a replica field theory describing finite dimensional site disordered spin systems by introducing the notion of grand canonical disorder, where the number of spins in the system is random but quenched. A general analysis of this field theory ... More
Splitting cycles in graphsApr 26 2012The goal of this paper is to describe a sufficient condition on cycles in graphs for which the edge ideal is splittable. We give an explicit splitting function for such ideals.
Stable Leader Election in Population Protocols Requires Linear TimeFeb 14 2015Aug 20 2016A population protocol *stably elects a leader* if, for all $n$, starting from an initial configuration with $n$ agents each in an identical state, with probability 1 it reaches a configuration $\mathbf{y}$ that is correct (exactly one agent is in a special ... More
Integrals derived from the doubling methodOct 21 2018In this note, we use a basic identity, derived from the generalized doubling integrals of \cite{C-F-G-K1}, in order to explain the existence of various global Rankin-Selberg integrals for certain $L$-functions. To derive these global integrals, we use ... More
Binary Survival in the Outer Solar SystemMay 06 2019As indicated by their special characteristics, the cold classical Kuiper belt objects (KBOs) formed and survived at 42-47 au. Notably, they show a large fraction of equal-size binaries whose formation is probably related to the accretion of KBOs themselves. ... More
The transverse proximity effect in the z ~ 2 Lyman-alpha forest suggests QSO episodic lifetimes of ~1 MyrSep 12 2008We look for signs of the H~I transverse proximity effect in the spectra of 130 QSO pairs, most with transverse separations in the plane of the sky of 0.1 -- 3 Mpc at z ~ 2.2. We expected to see a decrease in Lyman-alpha forest HI absorption in the spectrum ... More
Comet Encounters and Carbon 14Nov 26 2012The $^{14}$C production of shock-accelerated particles is calculated in terms of the total energy released in energetic particles. The recently reported 1.2% jump in the $^{14}$C content of the atmosphere in the year C.E. 775, it is found, would require ... More
Continuum Percolation for Quermass ModelJan 11 2012The continuum percolation for Markov (or Gibbs) germ-grain models is investigated. The grains are assumed circular with random radii on a compact support. The morphological interaction is the so-called Quermass interaction defined by a linear combination ... More
Randomized greedy algorithms for independent sets and matchings in regular graphs: Exact results and finite girth correctionsJul 08 2008We derive new results for the performance of a simple greedy algorithm for finding large independent sets and matchings in constant degree regular graphs. We show that for $r$-regular graphs with $n$ nodes and girth at least $g$, the algorithm finds an ... More
Two Identities relating Eisenstein series on classical groupsAug 05 2018In this paper we introduce two general identities relating Eisenstein series on split classical groups, as well as double covers of symplectic groups. The first identity can be viewed as an extension of the doubling construction introduced in [CFGK17]. ... More
The Detection of Two Distinct High Ionization States in a QSO Lyman Limit Absorption System: Evidence for Hierarchical Galaxy Formation at z ~ 3?Jan 19 1999We have detected two high ionization phases of gas in the z ~ 2.77 partial Lyman limit system (LLS) towards QSO 1157-3143. We detect the first phase by CIV and SiIV absorption, and the second phase -- which is either warmer or undergoing larger random ... More
Cortical prediction marketsJan 07 2014We investigate cortical learning from the perspective of mechanism design. First, we show that discretizing standard models of neurons and synaptic plasticity leads to rational agents maximizing simple scoring rules. Second, our main result is that the ... More
Banjo timbre from string stretching and frequency modulationJun 18 2014Sep 19 2014The geometry of a floating bridge on a drumhead soundboard produces string stretching that is first order in the amplitude of the bridge motion. This stretching modulates the string tension and consequently modulates string frequencies at acoustic frequencies. ... More
Heinz inequality for the unit ballApr 07 2015May 17 2015We first prove the following generalization of Schwarz lemma for harmonic mappings. Let $u$ be a harmonic mapping of the unit ball onto itself. Then we prove the inequality $\|u(x)-(1-\|x\|^2)/(1+\|x\|^2)^{n/2} u(0)\|\le U(|x| N)$. By using the Schwarz ... More
Energy-minimal diffeomorphisms between doubly connected Riemann surfacesAug 03 2011Apr 02 2012Let $N=(\Omega,\sigma)$ and $M=(\Omega^*,\rho)$ be doubly connected Riemann surfaces and assume that $\rho$ is a smooth metric with bounded Gauss curvature $\mathcal{K}$ and finite area. The paper establishes the existence of homeomorphisms between $\Omega$ ... More
A combinatorial interpretation for the identity Sum_{k=0}^{n} binom{n}{k} Sum_{j=0}^{k} binom{k}{j}^{3}= Sum_{k=0}^{n} binom{n}{k}^{2}binom{2k}{k}Dec 23 2007The title identity appeared as Problem 75-4, proposed by P. Barrucand, in Siam Review in 1975. The published solution equated constant terms in a suitable polynomial identity. Here we give a combinatorial interpretation in terms of card deals.
A Combinatorial Interpretation of j/n {kn}\choose{n+j}Apr 21 2006The identity j/n {kn}\choose{n+j} =(k-1) {kn-1}\choose{n+j-1}- {kn-1}\choose{n+j} shows that j/n {kn}\choose{n+j} is always an integer. Here we give a combinatorial interpretation of this integer in terms of lattice paths, using a uniformly distributed ... More
Bijections from Dyck paths to 321-avoiding permutations revisitedNov 16 2007There are (at least) three bijections from Dyck paths to 321-avoiding permutations in the literature, due to Billey-Jockusch-Stanley, Krattenthaler, and Mansour-Deng-Du. How different are they? Denoting them B,K,M respectively, we show that M = B \circ ... More
Illusions of phase coexistence: Comments on "Metastable liquid-liquid transition ..." by J. C. Palmer et al., Nature 510, 385 (2014)Jul 25 2014Aug 20 2014The recent paper cited above claims that a molecular simulation of one specific model of supercooled water establishes a stable interface separating two metastable liquid phases, which would imply the existence of metastable two-liquid criticality for ... More
Smooth dynamics and new theoretical ideas in nonequilibrium statistical mechanicsDec 31 1998This paper reviews various applications of the theory of smooth dynamical systems to conceptual problems of nonequilibrium statistical mechanics. We adopt a new point of view which has emerged progressively in recent years, and which takes seriously into ... More
An investigation of the false discovery rate and the misinterpretation of P valuesJul 20 2014Nov 20 2014The following proposition is justified from several different points of view. If you use P = 0.05 to suggest that you have made a discovery, you will be wrong at least 30 percent of the time. If, as is often the case, experiments are under-powered, you ... More
Partitions and Objective Indefiniteness in Quantum MechanicsJan 10 2014Mar 24 2014Classical physics and quantum physics suggest two meta-physical types of reality: the classical notion of a objectively definite reality with properties "all the way down," and the quantum notion of an objectively indefinite type of reality. The problem ... More
Nonvanishing cohomology classes on finite groups of Lie type with Coxeter number at most pJul 11 2014Feb 21 2015We prove that the degree $r(2p-3)$ cohomology of any finite group of Lie type over $\mathbb{F}_{p^r}$, with coefficients in characteristic $p$, is nonzero as long as its Coxeter number is at most $p$. We do this by providing a simple explicit construction ... More
Symmetry and the arrow of time in theoretical black hole astrophysicsJul 27 2015While the basic laws of physics seem time-reversal invariant, our understanding of the apparent irreversibility of the macroscopic world is well grounded in the notion of entropy. Because astrophysics deals with the largest structures in the Universe, ... More
Model Structures on Commutative Monoids in General Model CategoriesMar 26 2014Jun 05 2016We provide conditions on a monoidal model category $\mathcal{M}$ so that the category of commutative monoids in $\mathcal{M}$ inherits a model structure from $\mathcal{M}$ in which a map is a weak equivalence or fibration if and only if it is so in $\mathcal{M}$. ... More
Stop That Subversive Spreadsheet!Dec 16 2007This paper documents the formation of the European Spreadsheet Risks Interest Group (EuSpRIG and outlines some of the research undertaken and reported upon by interested parties in EuSpRIG publications
Asymmetries for neutral pion photoproduction in the threshold regionAug 10 2013We report on two pion-photoproduction measurements in the threshold region conducted in the A2 collaboration at MAMI with the almost 4{\pi} Crystal Ball detector. The first was with a linearly polarized photon beam and unpolarized liquid-hydrogen target. ... More
Deep Online Convex Optimization with Gated GamesApr 07 2016Methods from convex optimization are widely used as building blocks for deep learning algorithms. However, the reasons for their empirical success are unclear, since modern convolutional networks (convnets), incorporating rectifier units and max-pooling, ... More
A Survey of Satisfiability Modulo TheoryJun 15 2016Satisfiability modulo theory (SMT) consists in testing the satisfiability of first-order formulas over linear integer or real arithmetic, or other theories. In this survey, we explain the combination of propositional satisfiability and decision procedures ... More
Gabriel's Paper HornMar 26 2014Gabriel's horn is the famous mathematical object that has finite volume and infinite surface area. This article gives a template for making Gabriel's horn out of paper cones. It also describes the mathematics behind the construction of the template.
Representations of finite groups on modules over K-theory (with an appendix by Akhil Mathew)Mar 09 2015Let $G$ be a finite group, and let $\mathbf{K}_p$ denote the completion at $p$ of the complex $K$-theory spectrum. $\mathbf{K}_p$ is a commutative ring spectrum that in some ways is very similar to the usual ring $\mathbf{Z}_p$ of $p$-adic integers. We ... More
Morse theory and toric vector bundlesOct 19 2010Apr 12 2011Morelli's computation of the K-theory of a toric variety X associates a polyhedrally constructible function on a real vector space to every equivariant vector bundle E on X. The coherent-constructible correspondence lifts Morelli's constructible function ... More
Smith theory and geometric Hecke algebrasJul 19 2011In 1960 Borel proved a "localization" result relating the rational cohomology of a topological space X to the rational cohomology of the fixed points for a torus action on X. This result and its generalizations have many applications in Lie theory. In ... More
Specific Differential Entropy Rate Estimation for Continuous-Valued Time SeriesJun 08 2016We introduce a method for quantifying the inherent unpredictability of a continuous-valued time series via an extension of the differential Shannon entropy rate. Our extension, the specific entropy rate, quantifies the amount of predictive uncertainty ... More
Status of Radio and Acoustic Detection of Ultra-High Energy Cosmic Neutrinos and a Proposal on Reporting ResultsJan 18 2005Neutrino astronomy offers the possibility to perform extra-galactic observations well beyond the photon absorption cutoff above 50 TeV. Based on observations of cosmic rays, we already know that astrophysical sources produce particles with at least a ... More
Sets, Lists and Noncrossing PartitionsNov 29 2007Feb 07 2008Partitions of [n]={1,2,...,n} into sets of lists are counted by sequence number A000262 in the On-Line Encyclopedia of Integer Sequences. They are somewhat less numerous than partitions of [n] into lists of sets, A000670. Here we observe that the former ... More
Sharp estimates for pseudodifferential operators with symbols of limited smoothness and commutatorsAug 24 2005We consider here pseudo-differential operators whose symbol $\sigma(x,\xi)$ is not infinitely smooth with respect to $x$. Decomposing such symbols into four -sometimes five- components and using tools of paradifferential calculus, we derive sharp estimates ... More
Local rigid cohomology of singular pointsJan 08 2014Jul 27 2016We show that if two singular points $x' \in X'$ and $x \in X$ on schemes over a field $k$ of characteristic $p > 0$ are contact equivalent then the rigid cohomology spaces $H^{\bullet}_{rig, \{x\}}(X)$ and $H^{\bullet}_{rig, \{x'\}}(X')$ are isomorphic. ... More
A geometric approach to Voiculescu-Brown entropyApr 29 2003A basic problem in dynamics is to identify systems with positive entropy, i.e., systems which are "chaotic." While there is a vast collection of results addressing this issue in topological dynamics, the phenomenon of positive entropy remains by and large ... More
Metric Dimension Parameterized by Max Leaf NumberJun 04 2015The metric dimension of a graph is the size of the smallest set of vertices whose distances distinguish all pairs of vertices in the graph. We show that this graph invariant may be calculated by an algorithm whose running time is linear in the input graph ... More
Searching for SpaceshipsApr 10 2000Apr 26 2000We describe software that searches for spaceships in Conway's Game of Life and related two-dimensional cellular automata. Our program searches through a state space related to the de Bruijn graph of the automaton, using a method that combines features ... More
Linear Complexity Hexahedral Mesh GenerationSep 26 1998We show that any polyhedron forming a topological ball with an even number of quadrilateral sides can be partitioned into O(n) topological cubes, meeting face to face. The result generalizes to non-simply-connected polyhedra satisfying an additional bipartiteness ... More
Drawing Arrangement Graphs In Small Grids, Or How To Play PlanarityJul 31 2013We describe a linear-time algorithm that finds a planar drawing of every graph of a simple line or pseudoline arrangement within a grid of area O(n^{7/6}). No known input causes our algorithm to use area \Omega(n^{1+\epsilon}) for any \epsilon>0; finding ... More
The Graphs of Planar Soap BubblesJul 16 2012We characterize the graphs formed by two-dimensional soap bubbles as being exactly the 3-regular bridgeless planar multigraphs. Our characterization combines a local characterization of soap bubble graphs in terms of the curvatures of arcs meeting at ... More
Subgraph Isomorphism in Planar Graphs and Related ProblemsNov 09 1999We solve the subgraph isomorphism problem in planar graphs in linear time, for any pattern of constant size. Our results are based on a technique of partitioning the planar graph into pieces of small tree-width, and applying dynamic programming within ... More
Incremental and Decremental Maintenance of Planar WidthSep 21 1998May 04 2000We present an algorithm for maintaining the width of a planar point set dynamically, as points are inserted or deleted. Our algorithm takes time O(kn^epsilon) per update, where k is the amount of change the update causes in the convex hull, n is the number ... More
Required experimental accuracy to select between supersymmetrical modelsApr 29 2003We will present a method to decide a priori whether various supersymmetrical scenarios can be distinguished based on sparticle mass data alone. For each model, a scan over all free SUSY breaking parameters reveals the extent of that model's physically ... More
The TreeBanker: a Tool for Supervised Training of Parsed CorporaMay 07 1997Jul 02 1997I describe the TreeBanker, a graphical tool for the supervised training involved in domain customization of the disambiguation component of a speech- or language-understanding system. The TreeBanker presents a user, who need not be a system expert, with ... More
Justifying and Improving Meta-Agent Conflict-Based SearchOct 23 2014The Meta-Agent Conflict-Based Search~(MA-CBS) is a recently proposed algorithm for the multi-agent path finding problem. The algorithm is an extension of Conflict-Based Search~(CBS), which automatically merges conflicting agents into meta-agents if the ... More
Braid Group CryptographyNov 26 2007Sep 27 2008In the last decade, a number of public key cryptosystems based on com- binatorial group theoretic problems in braid groups have been proposed. We survey these cryptosystems and some known attacks on them. This survey includes: Basic facts on braid groups ... More
Phase Transitions in Non-Equilibrium SystemsMar 27 2000Apr 03 2000Phase transitions and critical behavior of driven systems are reviewed. Models exhibiting phase transitions, spontaneous symmetry breaking, phase separation and coarsening processes in d=1 dimension are discussed.
Evaporation of extrasolar planetsJul 11 2008Atomic hydrogen escaping from the extrasolar giant planet HD209458b provides the largest observational signature ever detected for an extrasolar planet atmosphere. In fact, the upper atmosphere of this planet is evaporating. Observational evidences and ... More
Vlasov-Maxwell, self-consistent electromagnetic wave emission simulations in the solar coronaAug 13 2010Oct 20 20101.5D Vlasov-Maxwell simulations are employed to model electromagnetic emission generation in a fully self-consistent plasma kinetic model for the first time in the solar physics context. The simulations mimic the plasma emission mechanism and Larmor drift ... More
Verblunsky Coefficients With Coulomb-Type DecayDec 28 2004We show that probability measures on the unit circle associated with Verblunsky coefficients obeying a Coulomb-type decay estimate have no singular continuous component.
Understanding galaxy formation with ISO deep surveysMar 17 2005We present the results obtained through the various ISO extragalactic deep surveys. While IRAS revealed the existence of galaxies forming stars at a rate of a few tens (LIRGs) or even hundreds (ULIRGs) solar masses in the local universe, ISO not only ... More
Existence of minimizers for Kohn-Sham within the Local Spin Density ApproximationApr 20 2014The purpose of this article is to extend the work by Anantharaman and Canc\`es [1], and prove the existence of minimizers for the spin-polarized Kohn-Sham model in the presence of a magnetic field within the local spin density approximation. We show that ... More
Pion and photon production in heavy ion collisionsMar 02 2009Measurement of neutral pions and direct photons are closely connected experimentally, on the other hand they probe quite different aspects of relativistic heavy ion collisions. In this short review of the $\pi^0$ results from the PHENIX experiment at ... More
Compton Sailing and Strong PolarizationSep 03 2003May 24 2004It is noted that a surface layer of matter in contact with a sufficiently super-Eddington, radially combed photon flux typically attains a relativistic coasting state whereby the radiation does not accelerate the matter. Radiation that scatters off this ... More
Ongoing Space Physics - Astrophysics ConnectionsMar 16 2005I review several ongoing connections between space physics and astrophysics: a) Measurements of energetic particle spectra have confirmed theoretical prediction of the highest energy to which shocks can accelerate particles, and this has direct bearing ... More
Monomials of q and q,t-characters for non simply-laced quantum affinizationsApr 08 2004Feb 04 2005Nakajima introduced the morphism of q,t-characters for finite dimensional representation of simply-laced quantum affine algebras : it is a t-deformation of the Frenkel-Reshetikhin's morphism of q-characters (sum of monomials in infinite variables). In ... More
t-analogues des operateurs d'ecrantage associes aux q-caracteres (t-analogs of screening operators related to q-characters)Dec 20 2001Dec 27 2001Frenkel and Reshetikhin introduced screening operators related to q-characters of finite dimensional representations of quantum affine algebras. We propose t-analogs of screening operators related to Nakajima's q,t-characters with the same properties ... More
Modeling Endogenous Social Networks: the Example of Emergence and Stability of Cooperation without RefusalDec 19 2005Aggregated phenomena in social sciences and economics are highly dependent on the way individuals interact. To help understanding the interplay between socio-economic activities and underlying social networks, this paper studies a sequential prisoner's ... More
Non-abelian higher gauge theory and categorical bundleFeb 10 2012Sep 06 2016A gauge theory is associated with a principal bundle endowed with a connection permitting to define horizontal lifts of paths. The horizontal lifts of surfaces cannot be defined into a principal bundle structure. An higher gauge theory is an attempt to ... More
Adiabatic quantum control hampered by entanglementOct 15 2013Jun 16 2014We study defects in adiabatic control of a quantum system caused by the entanglement of the system with its environment. Such defects can be assimilated to decoherence processes due to perturbative couplings between the system and the environment. To ... More
Twistor Strings for N=8 SupergravityJan 05 2013This paper presents a worldsheet theory describing holomorphic maps to twistor space with N fermionic directions. The theory is anomaly free when N=8. Via the Penrose transform, the vertex operators correspond to an N=8 Einstein supergravity multiplet. ... More
Garside categories, periodic loops and cyclic setsOct 26 2006Garside groupoids, as recently introduced by Krammer, generalise Garside groups. A weak Garside group is a group that is equivalent as a category to a Garside groupoid. We show that any periodic loop in a Garside groupoid $\CG$ may be viewed as a Garside ... More
Topology of complex reflection arrangementsNov 29 2004Let $V$ be a finite dimensional complex vector space and $W\subset \GL(V)$ be a finite complex reflection group. Let $V^{\reg}$ be the complement in $V$ of the reflecting hyperplanes. A classical conjecture predicts that $V^{\reg}$ is a $K(pi,1)$ space. ... More
String Theory and Quantum ChromodynamicsSep 11 2007I review recent progress on the connection between string theory and quantum chromodynamics in the context of the gauge/gravity duality. Emphasis is placed on conciseness and conceptual aspects rather than on technical details. Topics covered include ... More
sl(2)_{-1/2} and the Triplet ModelJan 22 2010Mar 29 2010Conformal field theories with sl(2)_{-1/2} symmetry are studied with a view to investigating logarithmic structures. Applying the parafermionic coset construction to the non-logarithmic theory, a part of the structure of the triplet model is uncovered. ... More
sl^(2)_{-1/2}: A Case StudyOct 20 2008Jan 09 2009The construction of the non-logarithmic conformal field theory based on sl^(2)_{-1/2} is revisited. Without resorting to free-field methods, the determination of the spectrum and fusion rules is streamlined and the beta gamma ghost system is carefully ... More
Multiple field inflationFeb 07 2007Inflation offers a simple model for very early evolution of our Universe and the origin of primordial perturbations on large scales. Over the last 25 years we have become familiar with the predictions of single-field models, but inflation with more than ... More
String-inspired cosmologyMar 12 2002I discuss cosmological models either derived from, or inspired by, string theory or M-theory. In particular I discuss solutions in the low-energy effective theory and the role of the dilaton, moduli and antisymmetric form fields in the dimensionally reduced ... More
First Order Inflation in General RelativityJul 20 1994I give a general formulation of the constraints on models of inflation ended by a first order phase transition arising from the requirement that they do not produce too many large (observable) true vacuum voids -- the `big bubble problem'. It is shown ... More
Appropriate and Inappropriate Estimation TechniquesMar 27 2013Mode {also called MAP} estimation, mean estimation and median estimation are examined here to determine when they can be safely used to derive {posterior) cost minimizing estimates. (These are all Bayes procedures, using the mode. mean. or median of the ... More
Towards a Normative Theory of Scientific EvidenceMar 27 2013A scientific reasoning system makes decisions using objective evidence in the form of independent experimental trials, propositional axioms, and constraints on the probabilities of events. As a first step towards this goal, we propose a system that derives ... More
Some improvements of the Katznelson-Tzafriri theorem on Hilbert spaceOct 06 2014This paper extends two recent improvements in the Hilbert space setting of the well-known Katznelson-Tzafriri theorem by establishing both a version of the result valid for bounded representations of a large class of abelian semigroups and a quantified ... More
Quantum Vortex Strings: A ReviewSep 30 2008The quantum worldsheet dynamics of vortex strings contains information about the 4d non-Abelian gauge theory in which the string lives. Here I tell this story. The string worldsheet theory is typically some variant of the CP^{N-1} sigma-model, describing ... More
The Quantum Dynamics of Heterotic Vortex StringsMar 26 2007We study the quantum dynamics of vortex strings in N=1 SQCD with U(N_c) gauge group and N_f=N_c quarks. The classical worldsheet of the string has N=(0,2) supersymmetry, but this is broken by quantum effects. We show how the pattern of supersymmetry breaking ... More
Comments on Condensates in Non-Supersymmetric Orbifold Field TheoriesDec 19 2002Mar 25 2003Non-supersymmetric orbifolds of N=1 super Yang-Mills theories are conjectured to inherit properties from their supersymmetric parent. We examine this conjecture by compactifying the Z_2 orbifold theories on a spatial circle of radius R. We point out that ... More
The Moduli Space of Noncommutative VorticesOct 01 2002Oct 15 2002The abelian Higgs model on the noncommutative plane admits both BPS vortices and non-BPS fluxons. After reviewing the properties of these solitons, we discuss several new aspects of the former. We solve the Bogomoln'yi equations perturbatively, to all ... More
A Note on 1/4-BPS StatesJan 31 1999We study classical solutions of N=4 super Yang-Mills theories that are invariant under 1/4 of the supersymmetry generators. Expressions for the mass and electric charge of the configurations are derived as functions on the monopole moduli space. These ... More
Mirror Mirror On The Wall: On 2d Black Holes and Liouville TheoryMar 18 2003Jun 30 2003We present a novel derivation of the duality between the two-dimensional Euclidean black hole and supersymmetric Liouville theory. We realise these (1+1)-dimensional conformal field theories on the worldvolume of domain walls in a (2+1)-dimensional gauge ... More
Dynamics of N=2 Supersymmetric Chern-Simons TheoriesMay 19 2000Aug 21 2000We discuss several aspects of three dimensional N=2 supersymmetric gauge theories coupled to chiral multiplets. The generation of Chern-Simons couplings at low-energies results in novel behaviour including compact Coulomb branches, non-abelian gauge symmetry ... More
Nearest Neighbor Network TraversalFeb 20 2007A mobile agent in a network wants to visit every node of an n-node network, using a small number of steps. We investigate the performance of the following ``nearest neighbor'' heuristic: always go to the nearest unvisited node. If the network graph never ... More
Quantum Algorithms for Tree Isomorphism and State SymmetrizationNov 18 2010Apr 25 2011The graph isomorphism problem is theoretically interesting and also has many practical applications. The best known classical algorithms for graph isomorphism all run in time super-polynomial in the size of the graph in the worst case. An interesting ... More
Calculation of the metric in the Hilbert space of a PT-symmetric model via the spectral theoremJul 12 2007In a previous paper (arXiv:math-ph/0604055) we introduced a very simple PT-symmetric non-Hermitian Hamiltonian with real spectrum and derived a closed formula for the metric operator relating the problem to a Hermitian one. In this note we propose an ... More
Decoherence and Ontology, or: How I Learned To Stop Worrying And Love FAPPNov 09 2011I make the case that the Universe according to unitary (no-collapse) quantum theory has a branching structure, and so can literally be regarded as a "many-worlds" theory. These worlds are not part of the fundamental ontology of quantum theory - instead, ... More
Gravity, Entropy, and Cosmology: In Search of ClarityJul 03 2009I discuss the statistical mechanics of gravitating systems and in particular its cosmological implications, and argue that many conventional views on this subject in the foundations of statistical mechanics embody significant confusion; I attempt to provide ... More
What is orthodox quantum mechanics?Apr 20 2016What is called "orthodox" quantum mechanics, as presented in standard foundational discussions, relies on two substantive assumptions --- the projection postulate and the eigenvalue-eigenvector link --- that do not in fact play any part in practical applications ... More
Life and death in the tails of the GRW wave functionJul 17 2014It seems to be widely assumed that the only effect of the Ghirardi-Rimini-Weber (`GRW') dynamical collapse mechanism on the `tails' of the wavefunction (that is, the components of superpositions on which the collapse is \emph{not} centred) is to reduce ... More
Tunable photonic band gaps with coherently driven atoms in optical latticesJun 21 2007Optical lattice loaded with cold atoms can exhibit a tunable photonic band gap for a weak probe field under the conditions of electromagnetically induced transparency. This system possesses a number of advantageous properties, including reduced relaxation ... More
Cost-volume relationships for flows through a disordered networkFeb 14 2005May 19 2005In a network where the cost of flow across an edge is nonlinear in the volume of flow, and where sources and destinations are uniform, one can consider the relationship between total volume $v$ of flow through the network and the minimum cost $c = Psi(v)$ ... More
S-hull: a fast radial sweep-hull routine for Delaunay triangulationMar 18 2016A new O(nlog(n)) algorithm is presented for performing Delaunay triangulation of sets of 2D points. The novel component of the algorithm is a radially propagating \emph{sweep-hull} (sequentially created from the radially sorted set of 2D points, giving ... More
A PAC-Bayesian Tutorial with A Dropout BoundJul 08 2013This tutorial gives a concise overview of existing PAC-Bayesian theory focusing on three generalization bounds. The first is an Occam bound which handles rules with finite precision parameters and which states that generalization loss is near training ... More
The Phase Structure of Supersymmetric Sp(2N_c) Gauge Theories with an AdjointAug 14 2009Nov 13 2009We study the phase structure of N = 1 supersymmetric Sp(2N_c) gauge theories with 2N_f fundamentals, an adjoint, and vanishing superpotential. Using a-maximization, we derive analytic expressions for the values of N_f below which the first several gauge-invariant ... More
Mixed state Pauli channel parameter estimationAug 29 2012The accuracy of any physical scheme used to estimate the parameter describing the strength of a single qubit Pauli channel can be quantified using standard techniques from quantum estimation theory. It is known that the optimal estimation scheme, with ... More
Discrimination of unitary transformations in the Deutsch-Jozsa algorithmFeb 23 2010We describe a general framework for regarding oracle-assisted quantum algorithms as tools for discriminating between unitary transformations. We apply this to the Deutsch-Jozsa problem and derive all possible quantum algorithms which solve the problem ... More