Results for "Ronald Holzlöhner"
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Magnetometry with Mesospheric SodiumDec 22 2009Measurement of magnetic fields on the few-hundred-kilometer length scale is significant for a variety of geophysical applications including mapping of crustal magnetism and ocean-circulation measurements, yet available techniques for such measurements ... More The blowup formula for Donaldson invariantsMay 09 1994Jul 07 1994In this paper we present a formula which relates the Donaldson invariants of a 4-manifold X with the Donaldson invariants of its blowup X#-CP(2). This blow-up formula is independent of X and involves sigma-functions associated to a naturally arising elliptic ... More Rational Blowdowns of Smooth 4-ManifoldsMay 17 1995In this paper we introduce a surgical procedure, called a rational blowdown, for a smooth 4-manifold X and determine how this procedure affects both the Donaldson and Seiberg-Witten invariants of X. Contact process with mobile disorderMay 03 2009I study the absorbing-state phase transition in the one-dimensional contact process with mobile disorder. In this model the dilution sites, though permanently inactive, diffuse freely, exchanging positions with the other sites, which host a basic contact ... More Nonequilibrium Phase Transitions in Epidemics and SandpilesOct 01 2001Nonequilibrium phase transitions between an active and an absorbing state are found in models of populations, epidemics, autocatalysis, and chemical reactions on a surface. While absorbing-state phase transitions fall generically in the DP universality ... More Reweighting in nonequilibrium simulationsFeb 22 1999A simple reweighting scheme is proposed for Monte Carlo simulations of interacting particle systems, permitting one to study various parameter values in a single study, and improving efficiency by an order of magnitude. Unlike earlier reweighting schemes, ... More Optimal packing of polydisperse hard-sphere fluids IIApr 27 2000We consider the consequences of keeping the total surface fixed for a polydisperse system of $N$ hard spheres. In contrast with a similar model (J. Zhang {\it et al.}, J. Chem. Phys. {\bf 110}, 5318 (1999)), the Percus-Yevick and Mansoori equations of ... More A topologically induced 2-in/2-out operation on loop cohomologyAug 29 2011May 16 2012We apply the Transfer Algorithm introduced in arXiv:1106.5090 to transfer an A_\infty-algebra structure that cannot be computed using the classical Basic Perturbation Lemma. We construct a space X whose (base pointed) loop cohomology H = H^*(\Omega X; ... More Tori in symplectic 4-manifoldsNov 19 2003Sep 29 2004We study the question of how many embedded symplectic or Lagrangian tori can represent the same homology class in a simply connected symplectic 4-manifold. Symplectic surfaces in a fixed homology classFeb 04 1999Oct 08 1999The purpose of this paper is to investigate the following problem: For a fixed 2-dimensional homology class K in a simply connected symplectic 4-manifold, up to smooth isotopy, how many connected smoothly embedded symplectic submanifolds represent K? ... More Modelling and Computing Homotopy Types: IOct 24 2016The aim of this article is to explain a philosophy for applying higher dimensional Seifert-van Kampen Theorems, and how the use of groupoids and strict higher groupoids resolves some foundational anomalies in algebraic topology at the border between homology ... More Rain, power laws, and advectionOct 15 2002Localized rain events have been found to follow power-law size and duration distributions over several decades, suggesting parallels between precipitation and seismic activity [O. Peters et al., PRL 88, 018701 (2002)]. Similar power laws are generated ... More Supernova Detection in IceCube: Status and FutureFeb 08 2013The IceCube detector, located at the South Pole, is discussed as a detector for core collapse supernovae. The large flux of $\bar{\nu}_{e}$ from a Galactic supernova gives rise to Cherenkov light from positrons and electrons created in neutrino interactions ... More Modelling and Computing Homotopy Types: IOct 24 2016Feb 03 2017The aim of this article is to explain a philosophy for applying higher dimensional Seifert-van Kampen Theorems, and how the use of groupoids and strict higher groupoids resolves some foundational anomalies in algebraic topology at the border between homology ... More Duality theory for Markov processes: Part 1Feb 11 2010This is the first part of a possible monograph on the duality of Markov processes. It contains a proof of Fitzsimmons' existence theorem of a moderate Markov dual process relative to an excessive measure, m, together with the necessary preliminary material. ... More Computing Homotopy Types Using Crossed N-Cubes of GroupsSep 14 2001Aug 13 2006The aim of this paper is to explain how, through the work of a number of people, some algebraic structures related to groupoids have yielded algebraic descriptions of homotopy n-types. Further, these descriptions are explicit, and in some cases completely ... More Crossed modules and the homotopy 2-type of a free loop spaceMar 29 2010May 23 2010The question was asked by Niranjan Ramachandran: how to describe the fundamental groupoid of LX, the free loop space of a space X? We give an answer by assuming X to be the classifying space of a crossed module over a group, and then describe completely ... More Measurement-to-Track Association and Finite-Set StatisticsJan 05 2017Multi-hypothesis trackers (MHT's), which are based on the measurement-to-track association (MTA) concept, have long been asserted to be "Bayes-optimal." Recently, rather bolder claims have come to the fore: "The right model of the multitarget state is ... More Muon Collider: Plans, Progress and ChallengesApr 16 2012We in the physics community expect the LHC to uncover new physics in the next few years. The character and energy scale of the new physics remain unclear, but it is likely that data from the LHC will need to be complemented by information from a lepton ... More Phase coexistence far from equilibriumFeb 10 2016Investigation of simple far-from-equilibrium systems exhibiting phase separation leads to the conclusion that phase coexistence is not well defined in this context. This is because the properties of the coexisting nonequilibrium systems depend on how ... More Modeling multi-stage decision optimization problemsApr 23 2014Multi-stage optimization under uncertainty techniques can be used to solve long-term management problems. Although many optimization modeling language extensions as well as computational environments have been proposed, the acceptance of this technique ... More Evolutionary Optimization for Decision Making under UncertaintyJan 19 2014Optimizing decision problems under uncertainty can be done using a variety of solution methods. Soft computing and heuristic approaches tend to be powerful for solving such problems. In this overview article, we survey Evolutionary Optimization techniques ... More Evidence of Long Range Order in the Riemann Zeta FunctionOct 14 2012We have done a statistical analysis of some properties of the contour lines Im$(\zeta (s))$ = 0 of the Riemann zeta function. We find that this function is broken up into strips whose average width on the critical line does not appear to vary with height. ... More Nonabelian Algebraic TopologyJul 15 2004Jul 27 2004This talk gave a sketch of the contents and background to a book with the title `Nonabelian algebraic topology' being written under support of a Leverhulme Emeritus Fellowship (2002-2004) by the speaker and Rafael Sivera (Valencia). The aim is to give ... More Towards non commutative algebraic topologyMay 12 2003This is a slightly edited version of the transparencies for a seminar at UCL, May 7, 2003. It is intended to give a quick view of background, ideas, and some calculations, in the applicatioon of some non commutative methods to algebraic topology. A note on percolation in cocycle measuresAug 09 2006We describe infinite clusters which arise in nearest-neighbour percolation for so-called cocycle measures on the square lattice. These measures arise naturally in the study of random transformations. We show that infinite clusters have a very specific ... More Spin goups of super metrics and a Theorem of RogersFeb 15 2016We derive the canonical forms of super Riemannian metrics and the local isometry groups of such metrics. For certain super metrics we also compute the simply connected covering groups of the local isometry groups and interpret these as local spin groups ... More Geometry of Thin FilmsNov 23 2015Jan 12 2016We study ray optics in the context of double mirror systems, in the limit as the two mirrors approach one another (thin films). This leads to a novel set of differential equations on a mirror surface which have interesting structure as seen from the perspective ... More Double groupoids, matched pairs and then matched triplesApr 08 2011In this note we show that the known relation between double groupoids and matched pairs of groups may be extended, or seems to extend, to the triple case. The references give some other occurrences of double groupoids. Knots, Links, and 4-ManifoldsDec 18 1996Jan 10 1997In this paper we investigate the relationship between isotopy classes of knots and links in S^3 and the diffeomorphism types of homeomorphic smooth 4-manifolds. As a corollary of this initial investigation, we begin to uncover the surprisingly rich structure ... More Invariants for Lagrangian toriApr 25 2003Jul 09 2004We define an simple invariant of an embedded nullhomologous Lagrangian torus and use this invariant to show that many symplectic 4-manifolds have infinitely many pairwise symplectically inequivalent nullhomologous Lagrangian tori. We further show that ... More Pinwheels and nullhomologous surgery on 4-manifolds with b^+ = 1Apr 18 2010Apr 13 2011We present a method for finding embedded nullhomologous tori in standard 4-manifolds which can be utilized to change their smooth structure. As an application, we show how to obtain infinite families of simply connected smooth 4-manifolds with b^+ = 1 ... More Six Lectures on Four 4-ManifoldsOct 23 2006Jan 03 2007Despite spectacular advances in defining invariants for simply connected smooth and symplectic 4-dimensional manifolds and the discovery of effective surgical techniques, we still have been unable to classify simply connected smooth manifolds up to diffeomorphism. ... More Surfaces in 4-ManifoldsMay 29 1997In this paper we introduce a technique, called rim surgery, which can change a smooth embedding of an orientable surface of positive genus and nonnegative self-intersection in a smooth 4-manifold while leaving the topological embedding unchanged. Surfaces in 4-manifolds: AddendumNov 29 2005In this note we fill a gap in the proof of the main theorem (Theorem 1.2) of our paper 'Surfaces in 4-manifolds', Math. Res. Letters 4 (1997), 907-914. Surgery on Nullhomologous ToriNov 18 2011Nov 28 2011By studying the example of smooth structures on CP^2#3(-CP^2) we illustrate how surgery on a single embedded nullhomologous torus can be utilized to change the symplectic structure, the Seiberg-Witten invariant, and hence the smooth structure on a 4-manifold. ... More Evolutionary multi-stage financial scenario tree generationDec 08 2009Jan 18 2010Multi-stage financial decision optimization under uncertainty depends on a careful numerical approximation of the underlying stochastic process, which describes the future returns of the selected assets or asset categories. Various approaches towards ... More On point processes in multitarget trackingMar 08 2016The finite-set statistics (FISST) approach to multitarget tracking was introduced in the mid-1990s. Its current extended form dates from 2001. In 2008, an "elementary" alternative to FISST was proposed, based on "finite point processes" rather than RFS's. ... More Fractal rain distributions and chaotic advectionNov 17 2003Localized rain events have been found to follow power-law distributions over several decades, suggesting parallels between precipitation and seismic activity [O. Peters et al., PRL 88, 018701 (2002)]. Similar power laws can be generated by treating raindrops ... More Generic slow relaxation in a stochastic sandpileSep 25 2002Simulations of a stochastic fixed-energy sandpile in one and two dimensions reveal slow relaxation of the order parameter, even far from the critical point. The decay of the activity is best described by a stretched-exponential form. The persistence probability ... More Numerical analysis of the master equationOct 26 2001Applied to the master equation, the usual numerical integration methods, such as Runge-Kutta, become inefficient when the rates associated with various transitions differ by several orders of magnitude. We introduce an integration scheme that remains ... More Restricted sandpile revisitedJan 18 2006I report large-scale Monte Carlo studies of a one-dimensional height-restricted stochastic sandpile using the quasistationary simulation method. Results for systems of up to 50 000 sites yield estimates for critical exponents that differ significantly ... More Nonuniversal Critical Spreading in Two DimensionsOct 18 1995Continuous phase transitions are studied in a two dimensional nonequilibrium model with an infinite number of absorbing configurations. Spreading from a localized source is characterized by nonuniversal critical exponents, which vary continuously with ... More Modelling and Computing Homotopy Types: IOct 24 2016Nov 01 2016The aim of this article is to explain a philosophy for applying higher dimensional Seifert-van Kampen Theorems, and how the use of groupoids and strict higher groupoids resolves some foundational anomalies in algebraic topology at the border between homology ... More Discontinuous phase transition in a dimer lattice gasMay 27 2012I study a dimer model on the square lattice with nearest-neighbor exclusion as the only interaction. Detailed simulations using tomographic entropic sampling show that as the chemical potential is varied, there is a strongly discontinuous phase transition, ... More Scaling Behavior in the 3D Random Field $XY$ ModelJan 05 2018May 07 2018We have performed studies of the 3D random field $XY$ model on $L \times L \times L$ simple cubic lattices with periodic boundary conditions, with a random field strength of $h_r$ = 1.875, for $L = 64$ and $L = 96$, using a parallelized Monte Carlo algorithm. ... More The Deformation Complex For DG Hopf AlgebrasJun 29 2001Sep 11 2002Let H be a differential graded Hopf algebra over a field k. This paper gives an explicit construction of a triple cochain complex that defines the Hochschild-Cartier cohomology of H. A certain truncation of this complex is the appropriate setting for ... More Local behaviour of first passage probabilitiesJun 28 2010Suppose that S is an asymptotically stable random walk with norming sequence c_{n} and that T_{x} is the time that S first enters (x,\inf), where x\ge 0. The asymptotic behaviour of P(T_0=n) has been described in a recent paper of Vatutin and Wachtel, ... More Numerical Study of a Field Theory for Directed PercolationJul 12 1994A numerical method is devised for study of stochastic partial differential equations describing directed percolation, the contact process, and other models with a continuous transition to an absorbing state. Owing to the heightened sensitivity to fluctuationsattending ... More On point processes in multitarget trackingMar 08 2016Mar 02 2018The finite-set statistics (FISST) approach to multitarget tracking was introduced in the mid-1990s. Its current extended form dates from 2001. In 2008, an "elementary" alternative to FISST was proposed, based on "finite point processes" rather than RFS's. ... More Embeddability of Arrangements of Pseudocircles into the SphereAug 17 2005An arrangement of pseudocircles is a finite set of oriented closed Jordan curves each two of which cross each other in exactly two points. To describe the combinatorial structure of arrangements on closed orientable surfaces, in (Linhart, Ortner 2004) ... More Structure Relations in Special A_\infty-bialgebrasJun 22 2005Jun 22 2005We compute the structure relations in special A_\infty-bialgebras whose operations are limited to those defining the underlying A_\infty-(co)algebra substructure. Such bialgebras appear as the homology of certain loop spaces. Whereas structure relations ... More Bounds on the Number of Longest Common SubsequencesJan 28 2003Aug 06 2003This paper performs the analysis necessary to bound the running time of known, efficient algorithms for generating all longest common subsequences. That is, we bound the running time as a function of input size for algorithms with time essentially proportional ... More Approximation using scattered shifts of a multivariate functionFeb 18 2008The approximation of a general $d$-variate function $f$ by the shifts $\phi(\cdot-\xi)$, $\xi\in\Xi\subset \Rd$, of a fixed function $\phi$ occurs in many applications such as data fitting, neural networks, and learning theory. When $\Xi=h\Z^d$ is a dilate ... More Distribution of dust and stars in the GalaxyAug 20 2000Using far-infrared 240 micron and near-infrared K band data from the COBE/DIRBE instrument, we model the Galactic stellar and dust distribution. Making the assumption that the Galaxy is transparent in the 240 micron band, the dust emission is modeled ... More