Results for "Thomas Wijnen"

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Three in one go: consequential angular momentum loss can solve major problems of CV evolutionOct 14 2015The average white dwarf (WD) masses in cataclysmic variables (CVs) have been measured to significantly exceed those of single WDs, which is the opposite of what is theoretically expected. We present the results of binary population synthesis models taking ... More
The consequences of a nearby supernova on the early Solar SystemFeb 12 2018If the Sun was born in a relatively compact open cluster (half-mass radius ~3pc) with ~10^3 stars, it is quite likely that a massive (>10MSun) star was nearby when it exploded in a supernova. The repercussions of a supernova can be rather profound, and ... More
Empirical consequential angular momentum loss can solve long standing problems of CV evolutionDec 10 2015The observed orbital period distribution of cataclysmic variables (CVs), the space density derived from observations, and the observed orbital period minimum are known to disagree with theoretical predictions since decades. More recently, the white dwarf ... More
White dwarf masses in cataclysmic variablesMar 17 2015Apr 16 2015The white dwarf (WD) mass distribution of cataclysmic variables (CVs) has recently been found to dramatically disagree with the predictions of the standard CV formation model. The high mean WD mass among CVs is not imprinted in the currently observed ... More
Sélection de la structure d'un perceptron multicouches pour la réduction dun modèle de simulation d'une scierieDec 05 2008Simulation is often used to evaluate the relevance of a Directing Program of Production (PDP) or to evaluate its impact on detailed sc\'enarii of scheduling. Within this framework, we propose to reduce the complexity of a model of simulation by exploiting ... More
Infinite reduced words and the Tits boundary of a Coxeter groupJan 05 2013Sep 18 2014Let (W,S) be a finite rank Coxeter system with W infinite. We prove that the limit weak order on the blocks of infinite reduced words of W is encoded by the topology of the Tits boundary of the Davis complex X of W. We consider many special cases, including ... More
On the quantifier-free dynamic complexity of ReachabilityJun 13 2013Jan 28 2015The dynamic complexity of the reachability query is studied in the dynamic complexity framework of Patnaik and Immerman, restricted to quantifier-free update formulas. It is shown that, with this restriction, the reachability query cannot be dynamically ... More
First results from the FPGA/NIOS Adaptive FIR Filter Using Linear Prediction Implemented in the AERA Radio Stations to Reduce Narrow Band RFI for Radio Detection of Cosmic RaysJun 03 2014The FPGA/NIOS FIR filter based on linear prediction (LP) to suppress radio frequency interference (RFI) has been installed in several radio stations in the Auger Engineering Radio Array (AERA) experiment. AERA observes coherent radio emission from extensive ... More
Face-on accretion onto a protoplanetary discJul 04 2016Globular clusters (GCs) are known to harbor multiple stellar populations. To explain these observations Bastian et al. suggested a scenario in which a second population is formed by the accretion of enriched material onto the low-mass stars in the initial ... More
Spectral Correlations in the Crossover Transition from a Superposition of Harmonic Oscillators to the Gaussian Unitary EnsembleJul 20 1998We compute the spectral correlation functions for the transition from a harmonic oscillator towards the Gaussian Unitary Ensemble (GUE). We use a variant of the supersymmetry method to obtain analytical results in a fast and elegant way. In contrast to ... More
Thermodynamic formalism for transport coefficients with an application to the shear modulus and shear viscosityDec 07 2016We discuss Onsager's thermodynamic formalism for transport coefficients and apply it to the calculation of the shear modulus and shear viscosity of a monodisperse system of repulsive particles. We focus on the concept of extensive "distance" and intensive ... More
An optimization principle for the computation of MHD equilibria in the solar coronaDec 21 2006AIMS: We develop an optimization principle for computing stationary MHD equilibria. METHODS: Our code for the self-consistent computation of the coronal magnetic fields and the coronal plasma uses non-force-free MHD equilibria. Previous versions of the ... More
Probabilistic Reasoning about Actions in Nonmonotonic Causal TheoriesOct 19 2012We present the language {m P}{cal C}+ for probabilistic reasoning about actions, which is a generalization of the action language {cal C}+ that allows to deal with probabilistic as well as nondeterministic effects of actions. We define a formal semantics ... More
Elagage d'un perceptron multicouches : utilisation de l'analyse de la variance de la sensibilité des paramètresDec 04 2008The stucture determination of a neural network for the modelisation of a system remain the core of the problem. Within this framework, we propose a pruning algorithm of the network based on the use of the analysis of the sensitivity of the variance of ... More
Two-Variable Logic with Two Order RelationsOct 07 2011Mar 03 2012It is shown that the finite satisfiability problem for two-variable logic over structures with one total preorder relation, its induced successor relation, one linear order relation and some further unary relations is EXPSPACE-complete. Actually, EXPSPACE-completeness ... More
GAVO Tools for the Analysis of Stars and NebulaeJun 15 2007Within the framework of the German Astrophysical Virtual Observatory (GAVO), we provide synthetic spectra, simulation software for the calculation of NLTE model atmospheres, as well as necessary atomic data. This will enable a VO user to directly compare ... More
Finite group extensions and the Baum-Connes conjectureSep 13 2002Jul 29 2007In this note, we exhibit a method to prove the Baum-Connes conjecture (with coefficients) for extensions with finite quotients of certain groups which already satisfy the Baum-Connes conjecture. Interesting examples to which this method applies are torsion-free ... More
Quantization and the Issue of Time for Various Two-Dimensional Models of GravityAug 31 1993It is shown that the models of 2D Liouville Gravity, 2D Black Hole- and $R^2$-Gravity are {\em embedded} in the Katanaev-Volovich model of 2D NonEinsteinian Gravity. Different approaches to the formulation of a quantum theory for the above systems are ... More
Measuring the Accuracy of Linked Data IndicesMar 19 2016Being based on Web technologies, Linked Data is distributed and decentralised in its nature. Hence, for the purpose of finding relevant Linked Data on the Web, search indices play an important role. Also for avoiding network communication overhead and ... More
On the Holonomy of Kaluza-Klein metricsMay 06 2008We investigate Kaluza-Klein metrics with a recurrent light-like vector field over a pseudo-Riemannian manifold.
Modelling Epidemics on NetworksNov 21 2011Dec 15 2011Infectious disease remains, despite centuries of work to control and mitigate its effects, a major problem facing humanity. This paper reviews the mathematical modelling of infectious disease epidemics on networks, starting from the simplest Erdos-Renyi ... More
Anomalies and large N limits in matrix string theoryJun 20 1998May 13 1999We study the loop expansion for the low energy effective action for matrix string theory. For long string configurations we find the result depends on the ordering of limits. Taking $g_s\to 0$ before $N\to\infty$ we find free strings. Reversing the order ... More
The Symplectic Geometry of Polygons in the 3-sphereSep 20 2000We study the symplectic geometry of the moduli spaces $M_r=M_r(\s^3)$ of closed n-gons with fixed side-lengths in the 3-sphere. We prove that these moduli spaces have symplectic structures obtained by reduction of the fusion product of $n$ conjugacy classes ... More
Generalised network clustering and its dynamical implicationsJun 23 2010A parameterisation of generalised network clustering, in the form of four-motif prevalences, is presented. This involves three real parameters that are conditional on one- two- and three-motif prevalences. Interpretations of these real parameters are ... More
Non-Markovian stochastic epidemics in extremely heterogeneous populationsMar 12 2014A feature often observed in epidemiological networks is significant heterogeneity in degree. A popular modelling approach to this has been to consider large populations with highly heterogeneous discrete contact rates. This paper defines an individual-level ... More
Exact epidemic dynamics for generally clustered, complex networksJun 17 2010Oct 02 2012The last few years have seen remarkably fast progress in the understanding of statistics and epidemic dynamics of various clustered networks. This paper considers a class of networks based around a concept (the locale) that allows asymptotically exact ... More
Forbidden Induced SubgraphsOct 15 2016In descending generality I survey: five partial orderings of graphs, the induced-subgraph ordering, and examples like perfect, threshold, and mock threshold graphs. The emphasis is on how the induced subgraph ordering differs from other popular orderings ... More
Tutorial Note on Merging Matrix Elements with Parton ShowersMar 26 2015In this short note, I introduce to essential conceptual features and main building blocks of matrix element merging algorithms, operating on fixed order calculations both at leading order and next-to-leading order. The intention is purely pedagogical, ... More
Measured geodesic laminations in FlatlandJan 16 2015Since their introduction by Thurston, measured geodesic laminations on hyperbolic surfaces occur in many contexts. In this survey, we give a generalization of geodesic laminations on surfaces endowed with a half-translation structure, called flat laminations, ... More
Decompositions of Binomial Ideals in Macaulay 2Jun 29 2011The package Binomials contains implementations of specialized algorithms for binomial ideals, including primary decomposition into binomial ideals. The current implementation works in characteristic zero. Primary decomposition is restricted to binomial ... More
A new formula for $ζ$(2n + 1) (and how not to prove that $ζ$(5) is irrational)Aug 09 2016Using a new polylogarithmic identity, we express the values of $\zeta$ at odd integers 2n + 1 as integrals over unit n--dimensional hypercubes of simple functions involving products of logarithms. We then make several conjectures, based on numerical evidence, ... More
The Cornstarch FlamethrowerJun 06 2016Igniting cornstarch powder is a classic physics demonstration that showcases the rapid conduction of heat for a material in which the surface area is greater than the volume of its constituent particles. Including such a demonstration in a physics "magic ... More
Strong solidity of group factors from lattices in SO(n,1) and SU(n,1)Sep 12 2010We show that the group factors of ICC lattices in either SO(n,1) or SU(n,1), n \geq 2, are strongly solid in the sense of Ozawa and Popa. This strengthens a result of Ozawa and Popa showing that these factors do not have Cartan subalgebras.
Periodic excitations of bilinear quantum systemsMar 06 2011Aug 09 2012A well-known method of transferring the population of a quantum system from an eigenspace of the free Hamiltonian to another is to use a periodic control law with an angular frequency equal to the difference of the eigenvalues. For finite dimensional ... More
The obstruction to the existence of a loopless star productSep 30 2013Jan 15 2014We show that there is an obstruction to the existence of a star product defined by Kontsevich graphs without directed cycles.
Characteristic classes in deformation quantizationAug 21 2012Dec 03 2014In deformation quantization one can associate five characteristic functions to (stable) formality morphisms on cochains and chains and to "two-brane" formality morphisms. We show that these characteristic functions agree.
The Fell compactification and non-Hausdorff groupoidsNov 13 2009A compactification of Fell is applied to locally compact non-Hausdorff groupoids and yields locally compact Hausdorff groupoids. In the etale case, this construction provides a geometric picture for the left-regular representations introduced by Khoshkam ... More
Probabilistic Latent Semantic AnalysisJan 23 2013Probabilistic Latent Semantic Analysis is a novel statistical technique for the analysis of two-mode and co-occurrence data, which has applications in information retrieval and filtering, natural language processing, machine learning from text, and in ... More
Testing Quarkonium Production with Photoproduced $J/ψ+ γ$Nov 13 1996Jan 14 1997I compute the leading color-octet contributions to the process $\gamma + p \to J/\psi + \gamma (+ X)$ within the non-relativistic QCD (NRQCD) factorization formalism. In the color-singlet model, $J/\psi + \gamma$ can only be produced when the photon interacts ... More
Summing $O(β_0^n α_s^{n+1})$ Corrections to Top Quark DecaysJul 21 1997Order $\beta_0^n \alpha_s^{n+1}$ QCD corrections to top quark decays into $W^+$ and $H^+$ bosons are computed to all orders in perturbation theory. Predictions for the radiative corrections to the top quark width are compared with the estimates from BLM ... More
The $1/m_Q$ Expansion in QCD: Introduction and OverviewSep 22 1994A mini-review of the heavy mass expansion in QCD is given. We focus on exclusive semileptonic decays and some topics of recent interest in inclusive decays of heavy hadrons.
On Zippin's Embedding Theorem of Banach spaces into Banach spaces with basesAug 14 2014We present a new proof of Zippin's Embedding Theorem, that every separable reflexive Banach space embeds into one with shrinking and boundedly complete basis, and every Banach space with a separable dual embeds into one with a shrinking basis. This new ... More
Computing the Maslov index from singularities of a matrix Riccati equationOct 13 2015Oct 27 2015We study the Maslov index as a tool to analyze stability of steady state solutions to a reaction-diffusion equation in one spatial dimension. We show that the path of unstable subspaces associated to this equation is governed by a matrix Riccati equation ... More
Constrained randomization of time series dataSep 30 1999A new method is introduced to create artificial time sequences that fulfil given constraints but are random otherwise. Constraints are usually derived from a measured signal for which surrogate data are to be generated. They are fulfilled by minimizing ... More
Genealogy of Nonperturbative Quantum-Invariants of 3-Manifolds: The Surgical FamilyJan 21 1996Mar 22 1996We study the relations between the invariants $\tau_{RT}$, $\tau_{HKR}$, and $\tau_L$ of Reshetikhin-Turaev, Hennings-Kauffman-Radford, and Lyubashenko, respectively. In particular, we discuss explicitly how $\tau_L$ specializes to $\tau_{RT}$ for semisimple ... More
Mapping Class Group Actions on Quantum DoublesFeb 03 1994We study representations of the mapping class group of the punctured torus on the double of a finite dimensional possibly non-semisimple Hopf algebra that arise in the construction of universal, extended topological field theories. We discuss how for ... More
Asymptotic Consensus Without Self-ConfidenceJan 16 2013Mar 25 2015This paper studies asymptotic consensus in systems in which agents do not necessarily have self-confidence, i.e., may disregard their own value during execution of the update rule. We show that the prevalent hypothesis of self-confidence in many convergence ... More
An introduction to Differential Linear Logic: proof-nets, models and antiderivativesJun 06 2016Differential Linear Logic enriches Linear Logic with additional logical rules for the exponential connectives, dual to the usual rules of dereliction, weakening and contraction. We present a proof-net syntax for Differential Linear Logic and a categorical ... More
A statistical physics perspective on criticality in financial marketsOct 09 2013Jan 27 2014Stock markets are complex systems exhibiting collective phenomena and particular features such as synchronization, fluctuations distributed as power-laws, non-random structures and similarity to neural networks. Such specific properties suggest that markets ... More
Statistical pairwise interaction model of stock marketJun 20 2012Jan 27 2014Financial markets are a classical example of complex systems as they comprise many interacting stocks. As such, we can obtain a surprisingly good description of their structure by making the rough simplification of binary daily returns. Spin glass models ... More
Invasion-wave induced first-order phase transition in systems of active particlesMar 31 2013An Enskog-like kinetic equation for self-propelled particles is solved numerically. I study a density instability near the transition to collective motion and find that while hydrodynamics breaks down, the kinetic approach leads to soliton-like supersonic ... More
Continuum Study of Heavy Quark DiffusionApr 28 2015We report on a lattice investigation of heavy quark momentum diffusion within the pure SU(3) plasma above the deconfinement transition with the quarks treated to leading order in the heavy mass expansion. We measure the relevant "colour-electric" Euclidean ... More
Sources of false positives and false negatives in the STATCHECK algorithm: Reply to Nuijten et al. (2015)Oct 04 2016Oct 10 2016STATCHECK is an R algorithm designed to scan papers automatically for inconsistencies between test statistics and their associated p values (Nuijten et al., 2015). The goal of this comment is to point out an important and well-documented flaw in this ... More
Telling Breaking News Stories from Wikipedia with Social Multimedia: A Case Study of the 2014 Winter OlympicsMar 17 2014With the ability to watch Wikipedia and Wikidata edits in realtime, the online encyclopedia and the knowledge base have become increasingly used targets of research for the detection of breaking news events. In this paper, we present a case study of the ... More
A comparison theorem between Radon and Fourier-Laplace transforms for D-modulesOct 23 2012Feb 04 2015We prove a comparison theorem between the d-plane Radon transform and the Fourier-Laplace transform for D-modules. This generalizes results of Brylinski and d'Agnolo-Eastwood.
Algebraic mechanics as an accessible toy model demonstrating entropy generation from reversible microscopic dynamicsNov 13 2008One observes that a considerable level of confusion remains about some of those aspects of irreversibility, entropy generation and `the arrow of time' which actually are well understood. This demands that great care must be taken in any discussion of ... More
Guaranteed successful strategies for a square achievement game on an n by n gridSep 11 2011May 20 2012At some places (see the references) Martin Erickson describes a certain game: "Two players alternately write O's (first player) and X's (second player) in the unoccupied cells of an n x n grid. The first player (if any) to occupy four cells at the vertices ... More
Finite-size scaling tests for SU(3) lattice gauge theory with color sextet fermionsOct 16 2009The observed slow running of the gauge coupling in SU(3) lattice gauge theory with two flavors of color sextet fermions naturally suggests it is a theory with one relevant coupling, the fermion mass, and that at zero mass correlation functions decay algebraically. ... More
Volume scaling of Dirac eigenvalues in SU(3) lattice gauge theory with color sextet fermionsJun 24 2009I observe a rough volume-dependent scaling of the low eigenvalues of a chiral Dirac operator in lattice studies of SU(3) lattice gauge theory with two flavors of color sextet fermions, in its weak-coupling phase. The mean value of the ith eigenvalue scales ... More
Reweighting QCD simulations with dynamical overlap fermionsOct 03 2008I apply a recently developed algorithm for reweighting simulations of lattice QCD from one quark mass to another to simulations performed with overlap fermions in the epsilon regime. I test it by computing the condensate from distributions of the low ... More
Eigenvalue Decomposition of Meson CorrelatorsOct 27 2003Euclidean space hadronic correlators are computed in quenched QCD at small quark mass using truncations of quark propagators which include or exclude low eigenvalue eigenmodes of the Dirac operator. High modes provide the dominant contribution to parity ... More
Kaon B Parameter in Quenched QCDSep 08 2003I calculate the kaon B-parameter with a lattice simulation in quenched approximation. The lattice simulation uses an action possessing exact lattice chiral symmetry, an overlap action. Computations are performed at two lattice spacings, about 0.13 and ... More
Short distance current correlators: Comparing lattice simulations to the instanton liquidJun 01 2001Aug 01 2001Point to point correlators of currents are computed in quenched QCD using a chiral lattice fermion action, the overlap action. I compare correlators made of exact quark propagators with correlators restricted to low (less than 500 MeV) eigenvalue eigenmodes ... More
Oblique correction in a walking lattice theoryJun 18 2010I compute the difference of vector and axial vector current correlators in the weak coupling phase of (lattice-regulated) SU(3) gauge theory with two flavors of symmetric-representation dynamical fermions. This is a walking theory at the bare parameter ... More
Ginsparg-Wilson GamesAug 23 1999I implement a set of tricks for constructing lattice fermion actions which approximately realize the Ginsparg-Wilson relation, with very promising results from simulations.
Dimers, webs, and positroidsApr 12 2014We study the dimer model for a planar bipartite graph N embedded in a disk, with boundary vertices on the boundary of the disk. Counting dimer configurations with specified boundary conditions gives a point in the totally nonnegative Grassmannian. Considering ... More
The shape of a random affine Weyl group element and random core partitionsFeb 22 2011Sep 09 2015Let $W$ be a finite Weyl group and ${\hat{W}}$ be the corresponding affine Weyl group. We show that a large element in ${\hat{W}}$, randomly generated by (reduced) multiplication by simple generators, almost surely has one of $|W|$-specific shapes. Equivalently, ... More
The Linearisation Map in Algebraic K-TheoryAug 24 2005Let X be a pointed connected simplicial set with loop group G. The linearisation map in K-theory as defined by Waldhausen uses G-equivariant spaces. This paper gives an alternative description using presheaves of sets and abelian groups on the simplex ... More
Elliptic flow and nearly perfect fluidity in dilute Fermi gasesDec 16 2010In this contribution we summarize recent progress in understanding the shear viscosity of strongly correlated dilute Fermi gases. We discuss predictions from kinetic theory, and show how these predictions can be tested using recent experimental data on ... More
The Kohn-Luttinger Effect in Gauge TheoriesJun 02 2006Sep 07 2006Kohn and Luttinger showed that a many body system of fermions interacting via short range forces becomes superfluid even if the interaction is repulsive in all partial waves. In gauge theories such as QCD the interaction between fermions is long range ... More
Effective Theories of Dense and Very Dense MatterSep 27 2006In these lectures we discuss the uses of effective field theory in studying dense hadronic matter. We focus on two regimes in the phase diagram. At low baryon density nucleons can be described as non-relativistic point particles interacting via short ... More
Effective Theory of Superfluid Quark MatterFeb 03 2004We provide a brief introduction to the high density effective theory of QCD. As an application, we consider the instanton correction to the perturbatively generated gap in the color superconducting phase. We show that the instanton correction becomes ... More
Instantons and Monte Carlo Methods in Quantum MechanicsNov 08 2004In these lectures we describe the use of Monte Carlo simulations in understanding the role of tunneling events, instantons, in a quantum mechanical toy model. We study, in particular, a variety of methods that have been used in the QCD context, such as ... More
Instantons and Scalar Multiquark States: From Small to Large N_cSep 14 2003We study scalar quark-anti-quark and two-quark-two-anti-quark correlation functions in the instanton liquid model. We show that the instanton liquid supports a light scalar-isoscalar (sigma) meson, and that this state is strongly coupled to both $(\bar{q}q)$ ... More
The Pion-Nucleon Form Factor From QCD Sum RulesJun 29 1995QCD sum rules are used to calculate the $q^2$ dependence of the $\pi NN$ coupling $g_{\pi NN} (q^2)$ in the spacelike region $0.5 \ {\mbox{GeV}}^2 \lesssim q^2 \lesssim 1.5\ {\mbox{GeV}}^2$. We study the Borel sum rule for the three point function of ... More
Fermi liquid theory: A brief survey in memory of Gerald E. BrownMar 27 2014Apr 10 2014I present a brief review of Fermi liquid theory, and discuss recent work on Fermi liquid theory in dilute neutron matter and cold atomic gases. I argue that renewed interest in transport properties of quantum fluids provides fresh support for Landau's ... More
Fluid Dynamics and Viscosity in Strongly Correlated FluidsMar 04 2014Jun 20 2014We review the modern view of fluid dynamics as an effective low energy, long wavelength theory of many body systems at finite temperature. We introduce the concept of a nearly perfect fluid, defined by a ratio $\eta/s$ of shear viscosity to entropy density ... More
Sources of false positives and false negatives in the STATCHECK algorithm: Reply to Nuijten et al. (2016)Oct 04 2016Nov 15 2016STATCHECK is an R algorithm designed to scan papers automatically for inconsistencies between test statistics and their associated p values (Nuijten et al., 2016). The goal of this comment is to point out an important and well-documented flaw in this ... More
Automated Evaluation of One-Loop Six-Point Processes for the LHCMar 05 2009In the very near future the first data from LHC will be available. The searches for the Higgs boson and for new physics will require precise predictions both for the signal and the background processes. Tree level calculations typically suffer from large ... More
Spectroscopic madness--A golden age for amateursJan 04 2011Today, professional instrumentation is dominated by heavily oversubscribed telescopes which focus mainly on a limited number of "fashionable" research topics. As a result, time acquisition for massive star research, including extended observation campaigns, ... More
Generalized guidance equation for peaked quantum solitons: the single particle caseFeb 09 2016We study certain non-linear generalisations of the Schr{\"o}dinger equation which admit static solitonic 2 solutions in absence of external potential acting on the particle. We consider a class of solutions that can be written as a product of a solution ... More
Generalized guidance equation for peaked quantum solitons and effective gravityFeb 11 2016Apr 12 2016Bouncing oil droplets have been shown to follow de Broglie-Bohm like trajectories and at the same time they exhibit attractive and repulsive pseudo-gravitation. We propose a model aimed at rendering account of these phenomenological observations. It inspires, ... More
GL(n) equivariant Minkowski valuationsAug 12 2013A classification of all continuous GL(n) equivariant Minkowski valuations on convex bodies in $\mathbb{R}^n$ is established. Together with recent results of F.E. Schuster and the author, this article therefore completes the description of all continuous ... More
Finite-size scaling tests for spectra in SU(3) lattice gauge theory coupled to 12 fundamental flavor fermionsSep 06 2011I carry out a finite-size scaling study of the correlation length in SU(3) lattice gauge theory coupled to 12 fundamental flavor fermions, using recent data published by Fodor, Holland, Kuti, Nogradi and Schroeder. I make the assumption that the system ... More
Transition asymptotics for the Painlevé II transcendentFeb 11 2015Feb 26 2015We consider real-valued solutions $u=u(x|s),x\in\mathbb{R}$ of the second Painlev\'e equation $u_{xx}=xu+2u^3$ which are parametrized in terms of the monodromy data $s\equiv(s_1,s_2,s_3)\subset\mathbb{C}^3$ of the associated Flaschka-Newell system of ... More
Smooth densities for stochastic differential equations with jumpsFeb 13 2007Oct 02 2007We consider a solution to a generic Markovian jump diffusion and show that for positive times the law of the solution process has a smooth density with respect to Lebesgue measure under a uniform version of Hoermander's conditions. Unlike previous results ... More
A Thermodynamic Classification of Real NumbersNov 09 2008Mar 15 2009A new classification scheme for real numbers is given, motivated by ideas from statistical mechanics in general and work of Knauf and of Fiala and Kleban in particular. Critical for this classification of a real number will be the Diophantine properties ... More
Computing the Galois group of some parameterized linear differential equation of order twoOct 05 2011Feb 18 2014We extend Kovacic's algorithm to compute the differential Galois group of some second order parameterized linear differential equation. In the case where no Liouvillian solutions could be found, we give a necessary and sufficient condition for the integrability ... More
Free dynamical quantum groups and the dynamical quantum group SU_q(2)May 11 2012Oct 04 2012We introduce dynamical analogues of the free orthogonal and free unitary quantum groups, which are no longer Hopf algebras but Hopf algebroids or quantum groupoids. These objects are constructed on the purely algebraic level and on the level of universal ... More
Duality via cycle complexesAug 18 2006Nov 26 2008We show that Bloch's complex of relative zero-cycles can be used as a dualizing complex over perfect fields and number rings. This leads to duality theorems for torsion sheaves on arbitrary separated schemes of finite type over algebraically closed fields, ... More
KPP reaction-diffusion systems with loss inside a cylinder: convergence toward the problem with Robin boundary conditionsJul 21 2010We consider in this paper a reaction-diffusion system under a KPP hypothesis in a cylindrical domain in the presence of a shear flow. Such systems arise in predator-prey models as well as in combustion models with heat losses. Similarly to the single ... More
The number of beams in IMRT - theoretical investigations and implications for single-arc IMRTSep 17 2009The first purpose of this paper is to shed some new light on the old question of selecting the number of beams in intensity-modulated radiation therapy (IMRT). The second purpose is to illuminate the related issue of discrete static beam angles vs. rotational ... More
Theoretical Aspects of $b \to s γ$ TransitionsMar 29 2001Apr 25 2001In this talk some of the theoretical aspects of $b \to s \gamma$ transitions are discussed. The focus is on inclusive decays, since these can be computed more reliably. Topics covered are (1) perturbative QCD corrections, (2) non-perturbative contributions ... More
A sharp bilinear cone restriction estimateMay 01 2001The purpose of this paper is to prove an essentially sharp L^2 Fourier restriction estimate for light cones, of the type which is called bilinear in the recent literature.
Physics at ELSA, achievements and futureJan 24 2005At ELSA interesting results on baryon resonances have been obtained by the CB-ELSA, the CBELSA/TAPS and the SAPHIR collaborations. New resonances were found, in particular a new $\rm D_{15}(2070)$ decaying into $p\eta$, was recently observed by the CB-ELSA ... More
The search for missing baryon resonancesJan 11 2005Experiments with electromagnetic probes are promising to search for baryon resonances that have been predicted by quark models but have not yet been observed. Data sets from different experiments show interesting resonance structures possibly due to so ... More
Residual properties of 3-manifold groups I: Fibered and hyperbolic 3-manifoldsOct 11 2009Feb 01 2010Let $p$ be a prime. In this paper, we classify the geometric 3-manifolds whose fundamental groups are virtually residually $p$. Let $M=M^3$ be a virtually fibered 3-manifold. It is well-known that $G=\pi_1(M)$ is residually solvable and even residually ... More
Low-Prandtl-number Bénard-Marangoni convection in a vertical magnetic fieldJun 30 2009The effect of a homogeneous magnetic field on surface-tension-driven B\'{e}nard convection is studied by means of direct numerical simulations. The flow is computed in a rectangular domain with periodic horizontal boundary conditions and the free-slip ... More
Generically nef vector bundles and geometric applicationsJun 21 2011The cotangent bundle of a non-uniruled projective manifold is generically nef, due to a theorem of Miyaoka. We show that the cotangent bundle is actually generically ample, if the manifold is of general type and study in detail the case of intermediate ... More
Critical Wilson Lines in Toroidal Compactifications of Heteroric StringsSep 25 1992Critical values of Wilson lines and general background fields for toroidal compactifications of heterotic string theories are constructed systematically using Dynkin diagrams.