Results for "Ruth Misener"

total 1017took 0.12s
Data-driven optimization of processes with degrading equipmentOct 22 2018Jan 24 2019In chemical and manufacturing processes, unit failures due to equipment degradation can lead to process downtime and significant costs. In this context, finding an optimal maintenance strategy to ensure good unit health while avoiding excessive expensive ... More
Argumentation for Explainable Scheduling (Full Paper with Proofs)Nov 13 2018Feb 20 2019Mathematical optimization offers highly-effective tools for finding solutions for problems with well-defined goals, notably scheduling. However, optimization solvers are often unexplainable black boxes whose solutions are inaccessible to users and which ... More
Detecting Symmetry in Designing Heat Exchanger NetworksNov 07 2017Symmetry in mathematical optimisation is of broad and current interest. In problem classes such as mixed-integer linear programming (MILP), equivalent solutions created by symmetric variables and constraints may combinatorially increase the search space. ... More
Exact Lexicographic Scheduling and Approximate ReschedulingMay 09 2018Feb 06 2019In industrial scheduling, an initial planning phase may solve the nominal problem and a subsequent recovery phase may intervene to repair inefficiencies and infeasibilities, e.g. due to machine failures and job processing time variations. This work investigates ... More
Symmetry Detection for Quadratically Constrained Quadratic Programs Using Binary Layered GraphsDec 14 2017Jan 20 2019Symmetry in mathematical programming may lead to a multiplicity of solutions. In nonconvex optimisation, it can negatively affect the performance of the branch-and-bound algorithm. Symmetry may induce large search trees with multiple equivalent solutions, ... More
Design of Experiments for Model Discrimination Hybridising Analytical and Data-Driven ApproachesFeb 12 2018Healthcare companies must submit pharmaceutical drugs or medical devices to regulatory bodies before marketing new technology. Regulatory bodies frequently require transparent and interpretable computational modelling to justify a new healthcare technology, ... More
Heuristics with Performance Guarantees for the Minimum Number of Matches Problem in Heat Recovery Network DesignSep 14 2017Apr 11 2018Heat exchanger network synthesis exploits excess heat by integrating process hot and cold streams and improves energy efficiency by reducing utility usage. Determining provably good solutions to the minimum number of matches is a bottleneck of designing ... More
Design of Experiments for Model Discrimination Hybridising Analytical and Data-Driven ApproachesFeb 12 2018May 31 2018Healthcare companies must submit pharmaceutical drugs or medical devices to regulatory bodies before marketing new technology. Regulatory bodies frequently require transparent and interpretable computational modelling to justify a new healthcare technology, ... More
Mixed-Integer Convex Nonlinear Optimization with Gradient-Boosted Trees EmbeddedMar 02 2018Oct 05 2018Decision trees usefully represent sparse, high dimensional and noisy data. Having learned a function from this data, we may want to thereafter integrate the function into a larger decision-making problem, e.g., for picking the best chemical process catalyst. ... More
GPdoemd: a Python package for design of experiments for model discriminationOct 05 2018Jan 14 2019Model discrimination identifies a mathematical model that usefully explains and predicts a given system's behaviour. Researchers will often have several models, i.e.\ hypotheses, about an underlying system mechanism, but insufficient experimental data ... More
GPdoemd: a Python package for design of experiments for model discriminationOct 05 2018Mar 08 2019Model discrimination identifies a mathematical model that usefully explains and predicts a given system's behaviour. Researchers will often have several models, i.e. hypotheses, about an underlying system mechanism, but insufficient experimental data ... More
Bayesian Optimization with Dimension Scheduling: Application to Biological SystemsNov 17 2015Bayesian Optimization (BO) is a data-efficient method for global black-box optimization of an expensive-to-evaluate fitness function. BO typically assumes that computation cost of BO is cheap, but experiments are time consuming or costly. In practice, ... More
Frontiers of the Universe: What do we know, what do we understand?May 07 2002In this talk I summarize the topics addressed during the conference. We have discussed the most relevant cosmological observations of the last say 10 years and their implications for our understanding of the Universe. My finding throughout this meeting ... More
Cosmic Magnetic Fields and the CMBSep 08 2006I describe the imprint of primordial magnetic fields on the CMB. I show that these are observable only if the field amplitude is of the order of $B\gsim 10^{-9}G$ on Mpc scale. I further argue that such fields are strongly constrained by the stochastic ... More
Nonsingular global stringsJun 04 1996Oct 17 1997We examine the possibility that time dependence might remove the singular nature of global string spacetimes. We first show that this time dependence takes a specific form -- a de-Sitter like expansion along the length of the string and give an argument ... More
Global field dynamics and cosmological tructure formationNov 02 1994We discuss gravitational effects of global scalar fields and, especially, of global topological defects. We first give an introduction to the dynamics of global fields and the formation of defects. Next we investigate the induced gravitational fields, ... More
Macroscopic open strings and gravitational confinementAug 14 2002We consider classical solutions for strings ending on magnetically charged black holes in four-dimensional Kaluza-Klein theory. We examine the classical superstring and the global vortex, which can be viewed as a nonsingular model for the superstring. ... More
Clarifying perturbations in the ekpyrotic universeDec 04 2001Mar 22 2002In this note I try to clarify the problem of perturbations in the ekpyrotic universe. I write down the most general matching conditions and specify the choices taken by the two debating sides. I also bring up the problem of surface stresses which always ... More
The theory of CMB anisotropiesSep 27 2001This is a review of the theory of CMB anisotropies, an updated version of a course given at the troisieme cycle de la Suisse Romande. An introduction to gauge invariant cosmological perturbation theory is given and the theory CMB anisotropies is develiped ... More
Holographic Superconductivity with Gauss-Bonnet gravityDec 07 2010I review recent work on holographic superconductivity with Einstein-Gauss-Bonnet gravity, and show how the critical temperature of the superconductor depends on both gravitational backreaction and the Gauss-Bonnet parameter, using both analytic and numerical ... More
Loop amplitudes in gauge theories: modern analytic approachesDec 20 2010Mar 24 2011This article reviews on-shell methods for analytic computation of loop amplitudes, emphasizing techniques based on unitarity cuts. Unitarity techniques are formulated generally but have been especially useful for calculating one-loop amplitudes in massless ... More
BraneworldsJul 01 2005This course is an introduction to the physics of braneworlds. We concentrate on braneworlds with only one extra-dimension and discuss their gravity. We derive the gravitational equations on the brane from the bulk Einstein equation and explore some limits ... More
Inflating p-branesApr 30 2003We look for solutions in Einstein gravity corresponding to inflating braneworlds of arbitrary dimension and co-dimension. These solutions correspond to isolated sources (no long range fields). Using dynamical systems techniques, we show that there exists ... More
Anisotropies in the Cosmic Microwave Background: Theoretical FoundationsOct 29 1996The analysis of anisotropies in the cosmic microwave background (CMB) has become an extremely valuable tool for cosmology. We even have hopes that planned CMB anisotropy experiments may revolutionize cosmology. Together with determinations of the CMB ... More
Cosmic p-branesOct 27 1995Jan 31 1997We consider the metrics for cosmic strings and $p$-branes in spacetime dimension $N>4$, that is, we look for solutions to Einstein-Maxwell-Dilaton gravity in $N$-dimensions with boost symmetry in the $p$-directions along the brane. Focussing first in ... More
Light Deflection in Perturbed Friedmann UniversesJan 18 1994In this letter a new formula for light deflection is derived using only physically observable concepts. The general result is specialized to cosmological perturbation theory and expressed in terms of gauge--invariant perturbation variables. The resulting ... More
Early Reionization in CosmologyNov 17 1993The cosmic microwave background (CMB) anisotropies have turned out to represent one of the most stringent 'bottle necks' for scenarios of large scale structure formation. As a possibility to relax this constraint, it has been proposed that early reionization ... More
Nonsingular global string compactificationsNov 03 1999Nov 17 1999We consider an exotic `compactification' of spacetime in which there are two infinite extra dimensions, using a global string instead of a domain wall. By having a negative cosmological constant we prove the existence of a nonsingular static solution ... More
Geometrical constraints on dark energy modelsOct 15 2007This contribution intends to give a pedagogical introduction to the topic of dark energy (the mysterious agent supposed to drive the observed late time acceleration of the Universe) and to various observational tests which require only assumptions on ... More
Physics of Cosmic Microwave Background anisotropies and primordial fluctuationsSep 17 2001The physics of the origin and evolution of CMB anisotropies is described. I explain the idea and status of cosmic parameter estimation and follow it up with critical comments on its dependence on model assumptions and initial conditions.
Gauge Invariant Cosmological Perturbation TheoryNov 17 1993After an introduction to the problem of cosmological structure formation, we develop gauge invariant cosmological perturbation theory. We derive the first order perturbation equations of Einstein's equations and energy momentum ``conservation''. Furthermore, ... More
A New Construction of Isospectral Riemannian Nilmanifolds with ExamplesFeb 10 1995We present a new construction for obtaining pairs of higher-step isospectral Riemannian nilmanifolds and compare several resulting new examples. In particular, we present new examples of manifolds that are isospectral on functions, but not isospectral ... More
Rigidity of cosmic acceleration in a class of k-essence cosmologiesOct 05 2004We study the structural stability of a cosmic acceleration (inflation) in a class of k-essence cosmologies against changes in the shape of the potential. Those models may be viewed as generalized tachyon cosmologies and this analysis extends previous ... More
What do we really know about Dark Energy?Mar 28 2011Sep 25 2011In this paper I discuss what we truly know about dark energy. I shall argue that up to date our single indication for the existence of dark energy comes from distance measurements and their relation to redshift. Supernovae, CMB anisotropies and observations ... More
Thick ideals in equivariant and motivic stable homotopy categoriesMar 29 2015We study thick ideals in the stable motivic homotopy category SH(k) and in its subcategories of compact and of finite cellular objects. If k is a subfield of the complex or even the real numbers, then using comparison functors we find thick ideals corresponding ... More
Braneworld black holesApr 16 2008In these lectures, I give an introduction to and overview of braneworlds and black holes in the context of warped compactifications. I first describe the general paradigm of braneworlds, and introduce the Randall-Sundrum model. I discuss braneworld gravity, ... More
Continuous Families of Riemannian manifolds, isospectral on functions but not on 1-formsFeb 13 1997The purpose of this paper is to present the first continuous families of Riemannian manifolds isospectral on functions but not on 1-forms, and simultaneously, the first continuous families of Riemannian manifolds with the same marked length spectrum but ... More
The Marked Length Spectrum Versus the Laplace Spectrum on Forms on Riemannian NilmanifoldsOct 13 1995The subject of this paper is the relationship among the marked length spectrum, the length spectrum, the Laplace spectrum on functions, and the Laplace spectrum on forms on Riemannian nilmanifolds. In particular, we show that for a large class of three-step ... More
A Note on the Finiteness of Curvature at Cosmic String CuspsDec 05 1994We examine a Nambu-Goto string trajectory in the neighbourhood of a cusp and determine the extrinsic curvature invariants. These are demonstrated to be finite, in contradiction with naive expectation. Thus the Nambu action is a valid approximation for ... More
Cosmological perturbation theoryFeb 05 2004Sep 21 2004This is a review on cosmological perturbation theory. After an introduction, it presents the problem of gauge transformation. Gauge invariant variables are introduced and the Einstein and conservation equations are written in terms of these variables. ... More
Black string instabilities in anti-de Sitter spaceApr 13 2000Sep 25 2000We show how to extend the usual black string instability of vacuum or charged black p-branes to the anti-de Sitter background. The string fragments in an analogous fashion to the $\Lambda=0$ case, the main difference being that instead of a periodic array ... More
Signatures of Topological Defects in the Microwave Sky: An IntroductionFeb 28 1997An introduction to topological defects in cosmology is given. We discuss their possible relevance for structure formation. Especial emphasis is given on the signature of topological defects in the spectrum of anisotropies in the cosmic microwave background. ... More
Symmetries and assisted inflation in the DGP braneworld modelFeb 03 2004Oct 20 2004We present here the general transformation that leaves unchanged the form of the field equations for perfect fluid cosmologies in the DGP braneworld model. Specifically, a prescription for relating exact solutions with different equations of state is ... More
The Gregory-Laflamme instabilityJul 28 2011I give a brief review of the Gregory-Laflamme instability as originally found for a 5-dimensional black string. This is a chapter of the book "Black Holes in Higher Dimensions" to be published by Cambridge University Press (editor: G. Horowitz)
The Marked Length Spectrum vs. The Laplace Spectrum on Forms on Riemannian NilmanifoldsOct 05 1995The subject of this paper is the relationship among the marked length spectrum, the length spectrum, the Laplace spectrum on functions, and the Laplace spectrum on forms on Riemannian nilmanifolds. In particular, we show that for a large class of three-step ... More
Cosmological Strucure Formation with Topological DefectsMar 23 2000Structure formation with topological defects is described. The main differences from inflationary models are highlighted. The results are compared with recent observations. It is concluded that all the defect models studied so far are in disagreement ... More
The three burials of Melquiades DGPJan 10 2008In this talk I review three fatal flaws of the DGP braneworld model, which has been put forward as a possible model for late time acceleration without a cosmological constant: Ghosts, Cosmological Crashes, and Instability of the 5D vacuum. The talk is ... More
G1 Cosmologies with Gravitational and Scalar WavesDec 18 1998I present here a new algorithm to generate families of inhomogeneous massless scalar field cosmologies. New spacetimes, having a single isometry, are generated by breaking the homogeneity of massless scalar field $G_2$ models along one direction. As an ... More
Theory of the Interaction of Planetary Nebulae with the Interstellar MediumJan 02 2000The theory of the interaction of planetary nebulae with the interstellar medium is important for the interpretation of nebular morphologies that deviate from point symmetry. It can be used to probe the interstellar medium and its magnetic field. We emphasize ... More
An introduction to right-angled Artin groupsOct 23 2006Recently, right-angled Artin groups have attracted much attention in geometric group theory. They have a rich structure of subgroups and nice algorithmic properties, and they give rise to cubical complexes with a variety of applications. This survey article ... More
Searching for HyperbolicityAug 06 2017This is an expository paper, based on by a talk given at the AWM Research Symposium 2017. It is intended as a gentle introduction to geometric group theory with a focus on the notion of hyperbolicity, a theme that has inspired the field from its inception ... More
Gravitational waves from stochastic relativistic sources: primordial turbulence and magnetic fieldsMar 17 2006Sep 15 2006The power spectrum of a homogeneous and isotropic stochastic variable, characterized by a finite correlation length, does in general not vanish on scales larger than the correlation scale. If the variable is a divergence free vector field, we demonstrate ... More
Nested braneworlds and strong brane gravityApr 30 2001We find the gravitational field of a `nested' domain wall living entirely within a brane-universe, or, a localised vortex within a wall. For a vortex living on a critical Randall-Sundrum brane universe, we show that the induced gravitational field on ... More
Axisymmetric metrics in arbitrary dimensionsJun 16 2003Jul 10 2004We consider axially symmetric static metrics in arbitrary dimension, both with and without a cosmological constant. The most obvious such solutions have an SO(n) group of Killing vectors representing the axial symmetry, although one can also consider ... More
Radio Galaxies and the Acceleration of the Universe Beyond a Redshift of OneDec 04 2002Radio galaxies provide a means to determine the coordinate distance,the luminosity distance, the dimensionless luminosity distance, or the angular size distance to sources with redshifts as large as two. Dimensionless coodinate distances for 55 supernovae ... More
The Oscillating Universe: an Alternative to InflationOct 19 1995Jan 05 1996The aim of this paper is to show, that the 'oscillating universe' is a viable alternative to inflation. We remind that this model provides a natural solution to the flatness or entropy and to the horizon problem of standard cosmology. We study the evolution ... More
Tachyonic perturbations in AdS$_5$ orbifoldsSep 28 2004May 02 2005We show that scalar as well as vector and tensor metric perturbations in the Randall-Sundrum II braneworld allow normalizable tachyonic modes, i.e., possible instabilities. These instabilities require nonvanishing initial anisotropic stresses on the brane. ... More
Subgroups and quotient groups of automorphism groups of RAAGsSep 13 2009Mar 23 2010We study subgroups and quotients of outer automorphism groups of right-angled Artin groups (RAAGs). We prove that for all RAAGS, the outer automorphism group is residually finite and, for a large class of RAAGs, it satisfies the Tits alternative. We also ... More
Maximum likelihood estimation of mark-recapture-recovery models in the presence of continuous covariatesNov 05 2012Nov 29 2013We consider mark-recapture-recovery (MRR) data of animals where the model parameters are a function of individual time-varying continuous covariates. For such covariates, the covariate value is unobserved if the corresponding individual is unobserved, ... More
Replicability analysis for genome-wide association studiesSep 13 2012Apr 29 2014The paramount importance of replicating associations is well recognized in the genome-wide associaton (GWA) research community, yet methods for assessing replicability of associations are scarce. Published GWA studies often combine separately the results ... More
Black Hole Spins of Radio SourcesNov 12 2008Dec 16 2008A new approach to constraining or determining the spin of a massive black hole is proposed. A key parameter in the analysis is the dimensionless ratio, r, of the energy released to the mass of the hole. It is shown that the black hole spin, j, may be ... More
External leg corrections in the unitarity methodSep 23 2011Feb 11 2012Unitarity cuts diverge in the channel of a single massive external fermion. We propose an off-shell continuation of the momentum that allows a finite evaluation of the unitarity cuts. If the cut is taken with complete amplitudes on each side, our continuation ... More
N=1/2 Wess-Zumino model is renormalizableJul 17 2003Nov 21 2003The Wess-Zumino model on N=1/2 nonanticommutative superspace, which contains the dimension-6 term F^3, is shown to be renormalizable to all orders in perturbation theory, upon adding F and F^2 terms to the original Lagrangian. The renormalizability is ... More
Idealisers in Skew Group RingsNov 26 2018Let C be a commutative noetherian domain, G be a finitely generated abelian group which acts on C and B = C#G be the skew group ring. For a prime ideal I in C, we study the largest subring of B in which the right ideal IB becomes a two-sided ideal - the ... More
A rank-one CAT(0) group is determined by its Morse boundaryJul 21 2017The Morse boundary of a proper geodesic metric space is designed to encode hypberbolic-like behavior in the space. A key property of this boundary is that a quasi-isometry between two such spaces induces a homeomorphism on their Morse boundaries. In this ... More
The Extreme Overabundance of Molybdenum in Two Metal-Poor StarsAug 17 2011Nov 09 2011We report determinations of the molybdenum abundances in five mildly to extremely metal-poor turnoff stars using five Mo II lines near 2000A. In two of the stars, the abundance of molybdenum is found to be extremely enhanced, as high or higher than the ... More
Contracting Boundaries of CAT(0) SpacesAug 29 2013As demonstrated by Croke and Kleiner, the visual boundary of a CAT(0) group is not well-defined since quasi-isometric CAT(0) spaces can have non-homeomorphic boundaries. We introduce a new type of boundary for a CAT(0) space, called the contracting boundary, ... More
A lexicographic shellability characterization of geometric latticesAug 09 2011Oct 16 2013Geometric lattices are characterized in this paper as those finite, atomic lattices such that every atom ordering induces a lexicographic shelling given by an edge labeling known as a minimal labeling. Equivalently, geometric lattices are shown to be ... More
Global monopoles in dilaton gravitySep 12 1997Feb 11 1998We analyse the gravitational field of a global monopole within the context of low energy string gravity, allowing for an arbitrary coupling of the monopole fields to the dilaton. Both massive and massless dilatons are considered. We find that, for a massless ... More
Cramer's Transactional Interpretation and Causal Loop ProblemsAug 17 2004Tim Maudlin's argument for the inconsistency of Cramer's Transactional Interpretation (TI) of quantum theory has been considered in some detail by Joseph Berkovitz, who has provided a possible solution to this challenge at the cost of a significant empirical ... More
Nonthermal Radio Emission from Planetary NebulaeMar 23 1998In a recent analysis of the radio emission from the planetary nebula A30, Dgani, Evans & White (1998) claim that the emission, located in the inner region, is probably dominated by nonthermal emission. We propose a model to explain this. We assume that ... More
1-loop Color structures and sunny diagramsJun 05 2014Recently the space of tree level color structures for gluon scattering was determined in arXiv:1403.6837 together with its transformation properties under permutations. Here we generalize the discussion to loops, demonstrating a reduction of an arbitrary ... More
Testing braneworlds with the binary pulsarMay 20 2003Apr 30 2004In this letter we calculate the emission of gravity waves by the binary pulsar in the framework of five dimensional braneworlds. We consider only spacetimes with one compact extra-dimension. We show that the presence of additional degrees of freedom, ... More
Decoupling Transition I. Flux Lattices in Pure Layered SuperconductorsMay 02 2004May 29 2005We study the decoupling transition of flux lattices in a layered superconductors at which the Josephson coupling J is renormalized to zero. We identify the order parameter and related correlations; the latter are shown to decay as a power law in the decoupled ... More
Primordial Magnetic Fields and CausalityMay 05 2003Oct 29 2003We discuss the implications of causality on a primordial magnetic field. We show that the residual field on large scales is much more suppressed than usually assumed and that a helical component is even more reduced. Due to this strong suppression, even ... More
Dark Energy and Dark GravityNov 01 2007Dec 05 2007Observations provide increasingly strong evidence that the universe is accelerating. This revolutionary advance in cosmological observations confronts theoretical cosmology with a tremendous challenge, which it has so far failed to meet. Explanations ... More
Dynamical Casimir effect for gravitons in bouncing braneworldsApr 05 2007Nov 15 2007We consider a two-brane system in a five-dimensional anti-de Sitter spacetime. We study particle creation due to the motion of the physical brane which first approaches the second static brane (contraction) and then recedes from it(expansion). The spectrum ... More
CMB anisotropies caused by gravitational waves: A parameter studyFeb 26 1997May 26 1998Anisotropies in the cosmic microwave background radiation due to gravity waves are investigated. An initial spectrum of gravity waves may have been induced during an epoch of inflation. We study the propagation of such a spectrum in a Friedmann background ... More
Braneworld InstantonsJul 12 2001Nov 23 2001We derive the general equations of motion for a braneworld containing a (localized) domain wall. Euclideanization gives the geometry for braneworld false vacuum decay. We explicitly derive these instantons and compute the amplitude for false vacuum decay. ... More
The Instability of Charged Black Strings and p-BranesApr 13 1994We investigate the evolution of small perturbations around charged black strings and branes which are solutions of low energy string theory. We give the details of the analysis for the uncharged case which was summarized in a previous paper. We extend ... More
Quintom cosmologies admitting either tracking or phantom attractorsFeb 27 2006In this paper we investigate the evolution of a class of cosmologies fuelled by quintom dark energy and dark matter. Quintom dark energy is a hybrid of quintessence and phantom which involves the participation of two reals scalar fields playing the roles ... More
Spacetime decay of cones at strong couplingJun 16 2003Jun 30 2003We study time dependent solutions in dilaton gravity which correspond to the decay of conical spacetimes. In string theory this can be interpreted as a strong coupling limit of the decay of a non-supersymmetric orbifold spacetime with localized tachyons. ... More
On $r$-uniform hypergraphs with circumference less than $r$Jul 12 2018We show that for each $k\geq 4$ and $n>r\geq k+1$, every $n$-vertex $r$-uniform hypergraph with no Berge cycle of length at least $k$ has at most $\frac{(k-1)(n-1)}{r}$ edges. The bound is exact, and we describe the extremal hypergraphs. This implies ... More
Multivariate tests of association based on univariate testsMar 10 2016For testing two random vectors for independence, we consider testing whether the distance of one vector from a center point is independent from the distance of the other vector from a center point by a univariate test. In this paper we provide conditions ... More
Radio and the 1999 UK Total Solar EclipseMar 04 2017On the morning of the August 11th 1999, a total eclipse of the sun plunged Cornwall and parts of Devon into darkness. The event of the eclipse was bound to attract a great deal of scientific and media attention. Realizing that the differences in day-time/night-time ... More
Massive particles and unitarity cutsFeb 11 2012We present an extension of the spinor integration formalism of one loop amplitudes from the double-cut to the single-cut case. This technique can be applied for the computation of the tadpole coefficients. Moreover we describe an off-shell continuation ... More
Integral Coefficients for One-Loop AmplitudesNov 27 2007We present a set of algebraic functions for evaluating the coefficients of the scalar integral basis of a general one-loop amplitude. The functions are derived from unitarity cuts, but the complete cut-integral procedure has been carried out in generality ... More
What galaxy surveys really measureMay 26 2011Jul 04 2012In this paper we compute the quantity which is truly measured in a large galaxy survey. We take into account the effects coming from the fact that we actually observe galaxy redshifts and sky positions and not true spatial positions. Our calculations ... More
An explicit symmetric DGLA model of a triangleFeb 08 2018We give explicit formulae for a differential graded Lie algebra (DGLA) model of the triangle which is symmetric under the geometric symmetries of the cell. This follows the work of Lawrence-Sullivan on the (unique) DGLA model of the interval and of Gadish-Griniasty-Lawrence ... More
Information Rates of Minimal Non-Matroid-Related Access StructuresJan 23 2008In a secret sharing scheme, shares of a secret are distributed to participants in such a way that only certain predetermined sets of participants are qualified to reconstruct the secret. An access structure on a set of participants specifies which sets ... More
Two New Settings for Examples of von Neumann DimensionNov 28 2018Let $G=PSL(2,\mathbb{R})$, let $\Gamma$ be a lattice in $G$, and let $\mathcal{H}$ be an irreducible unitary representation of $G$ with square-integrable matrix coefficients. A theorem in [Goodman, de la Harpe, Jones 1989] states that the von Neumann ... More
H2 infrared line emission from the ionized region of planetary nebulaeDec 20 2010Feb 04 2011The analysis and interpretation of the H2 line emission from planetary nebulae have been done in the literature assuming that the molecule survives only in regions where the hydrogen is neutral, as in photodissociation, neutral clumps or shocked regions. ... More
Polyhedral Combinatorics of UPGMA ConesJun 07 2012Distance-based methods such as UPGMA (Unweighted Pair Group Method with Arithmetic Mean) continue to play a significant role in phylogenetic research. We use polyhedral combinatorics to analyze the natural subdivision of the positive orthant induced by ... More
The eta invariant on two-step nilmanifoldsOct 30 2012Jun 13 2016The eta invariant appears regularly in index theorems but is known to be directly computable from the spectrum only in certain examples of locally symmetric spaces of compact type. In this work, we derive some general formulas useful for calculating the ... More
Frobenius powers of non-complete intersectionsJun 27 2001Aug 02 2001For a commutative ring $R$ of characteristic $p$, let $\phi : R \to R$ be the Frobenius homomorphism and let $^{\phi^r}R$ denote the $R$-module structure on $R$ defined via the $r$-th power of the Frobenius. We show that the Tor functor against the Frobenius ... More
Garside structure for the braid group of G(e,e,r)Jun 11 2003We give a new presentation of the braid group $B$ of the complex reflection group $G(e,e,r)$ which is positive and homogeneous, and for which the generators map to reflections in the corresponding complex reflection group. We show that this presentation ... More
A free differential Lie algebra for the intervalOct 30 2006Oct 31 2006Using geometric methods we constructively show the existence of a unique completed free differential graded Lie algebra modelled on the interval, with three generators, a, b and e in degrees -1, -1 and 0, corresponding to the two 0-cells and one 1-cell, ... More
Microwave Background Anisotropies Induced by Global Scalar Fields: The Large N LimitDec 20 1996We present an analysis of CMB anisotropies induced by global scalar fields in the large N limit. In this limit, the CMB anisotropy spectrum can be determined without cumbersome 3D simulations. We determine the source functions and their unequal time correlation ... More
Uniformisation techniques for stochastic simulation of chemical reaction networksNov 02 2018This work considers the method of uniformisation for continuous-time Markov chains in the context of chemical reaction networks. Previous work in the literature has shown that uniformisation can be beneficial in the context of time-inhomogeneous models, ... More
False discovery rate controlling procedures for discrete testsDec 20 2011Jan 27 2014Benjamini and Hochberg (1995) proposed the false discovery rate (FDR) as an alternative to the family-wise error rate in multiple testing problems, and proposed a procedure to control the FDR. For discrete data this procedure may be highly conservative. ... More