Results for "Matthieu Bethermin"

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Towards a new modelling of gas flows in a semi-analytical model of galaxy formation and evolutionOct 18 2014Feb 02 2015We present an extended version of the semi-analytical model, GalICS. Like its predecessor, eGalICS applies a post-treatment of the baryonic physics on pre-computed dark-matter merger trees extracted from an N-body simulation. We review all the mechanisms ... More
Galaxy stellar mass assembly: the difficulty matching observations and semi-analytical predictionsOct 18 2014Feb 02 2015Semi-analytical models (SAMs) are currently the best way to understand the formation of galaxies within the cosmic dark-matter structures. While they fairly well reproduce the local stellar mass functions, correlation functions and luminosity functions, ... More
Panchromatic Study of the First Galaxies with Large ALMA ProgramsJan 04 2019Thanks to deep optical to near-IR imaging and spectroscopy, significant progress is made in characterizing the rest-frame UV to optical properties of galaxies in the early universe (z > 4). Surveys with Hubble, Spitzer, and ground-based facilities (Keck, ... More
Taking Census of Massive, Star-Forming Galaxies formed <1 Gyr After the Big BangMar 13 2019Two decades of effort have been poured into both single-dish and interferometric millimeter-wave surveys of the sky to infer the volume density of dusty star-forming galaxies (DSFGs, with SFR>100M$_\odot$ yr$^{-1}$) over cosmic time. Though obscured galaxies ... More
Dynamics on Trees of SpheresJun 24 2014We introduce the notion of dynamically marked rational maps. We study sequences of analytic conjugacy classes of rational maps which diverge in moduli space. In particular, we are interested in the notion of rescaling limits introduced by Jan Kiwi. In ... More
K-theorie equivariante des varietes de drapeaux et des varietes de Bott-SamelsonApr 22 2002The aim of this text is to give an explicit formula for the restriction to fixed points of a basis of the equivariant K-theory of the flag varieties and of the Bott-Samelson varieties.
Second order phase transitions induced by disorder in frustrated magnetsMar 19 2002Apr 04 2002We study the critical properties of three dimensional frustrated magnets, diluted with non-magnetic impurities. We show that these systems exhibit a second order phase transition, corresponding to a new universality class. In the pure case, the phase ... More
Automatic semigroups vs automaton semigroupsSep 29 2016We develop an effective and natural approach to interpret any semigroup admitting a special language of greedy normal forms as an automaton semigroup, namely the semigroup generated by a Mealy automaton encoding the behaviour of such a language of greedy ... More
Approximability of dynamical systems between trees of spheresAug 09 2014Sep 13 2017We study sequences of analytic conjugacy classes of rational maps which diverge in moduli space. In particular, we are interested in the notion of rescaling limits introduced by Jan Kiwi. In the continuity of [A1] we recall the notion of dynamical covers ... More
Compactification and trees of spheres coversAug 09 2014Sep 13 2017We already saw in [A1] that the space of dynamically marked rational maps can be identified to a subspace of the space of covers between trees of spheres on which there is a notion of convergence that makes it sequentially compact. In the following we ... More
Comparison bewteen multi-task and single-task oracle risks in kernel ridge regressionJul 19 2013In this paper we study multi-task kernel ridge regression and try to understand when the multi-task procedure performs better than the single-task one, in terms of averaged quadratic risk. In order to do so, we compare the risks of the estimators with ... More
Fast nielsen-thurston classification of braidsDec 01 2011Oct 24 2013We prove the existence of an algorithm which solves the reducibility problem in braid groups and runs in quadratic time with respect to the braid length for any fixed braid index.
Projective representations of mapping class groups in combinatorial quantizationDec 02 2018Dec 19 2018Let $\Sigma_{g,n}$ be a compact oriented surface of genus $g$ with $n$ open disks removed. The graph algebra $\mathcal{L}_{g,n}(H)$ was introduced by Alekseev--Grosse--Schomerus and Buffenoir--Roche and is a combinatorial quantization of the moduli space ... More
Modular group representations in combinatorial quantization with non-semisimple Hopf algebrasMay 02 2018Feb 22 2019Let $\Sigma_{g,n}$ be a compact oriented surface of genus $g$ with $n$ open disks removed. The algebra $\mathcal{L}_{g,n}(H)$ was introduced by Alekseev--Grosse--Schomerus and Buffenoir--Roche and is a combinatorial quantization of the moduli space of ... More
An integrabilist approach of out-of-equilibrium statistical physics modelsAug 08 2017In the first part of the thesis we construct models, called integrable, in which we can perform exact computations of physical quantities. We introduce several new out-of-equilibrium models that are obtained by solving, in specific cases, the Yang-Baxter ... More
Simulation of a Local Time Fractional Stable MotionDec 19 2007Jul 16 2008In this paper, we simulate sample paths of a class of symmetric $\alpha$-stable processes using their series expression. We will develop a result in the approximation of shot-noise series. And finally, we will get a convergence rate for the approximation. ... More
Optimal model selection in density estimationOct 09 2009Jul 26 2010We build penalized least-squares estimators using the slope heuristic and resampling penalties. We prove oracle inequalities for the selected estimator with leading constant asymptotically equal to 1. We compare the practical performances of these methods ... More
The far infra-red SEDs of main sequence and starburst galaxiesJul 19 2016Jan 19 2017We compare observed far infra-red/sub-millimetre (FIR/sub-mm) galaxy spectral energy distributions (SEDs) of massive galaxies ($M_{\star}\gtrsim10^{10}$ $h^{-1}$M$_{\odot}$) derived through a stacking analysis with predictions from a new model of galaxy ... More
Rigidity and intermediate phases in glasses driven by speciationMar 31 2006The rigid to floppy transitions and the associated intermediate phase in glasses are studied in the case where the local structure is not fully determined from the macroscopic concentration. The approach uses size increasing cluster approximations and ... More
Solvable models of Glass TransitionSep 02 1999Simple statistical agglomeration models can provide a universal link between the local structure and the glass transition temperature in network glasses. We first stress the physical features of the models and the hypothesis made, and then show how to ... More
Elasticity of soft particles and colloids near Random Close PackingJun 28 2008Jul 14 2009Assemblies of purely repulsive and frictionless particles, such as emulsions or hard spheres, display very curious properties near their jamming transition, which occurs at the random close packing for mono-disperse spheres. Although such systems do not ... More
On the homogenization of the Stokes problem in a perforated domainApr 15 2016Sep 06 2016We consider the Stokes equations on a bounded perforated domaincompleted with non-zero constant boundary conditions on the holes. We investigate configurations forwhich the holes are identical spheres and their number N goes to infinity while their radius1/N ... More
Summability Condition and Rigidity for Finite Type MapsFeb 16 2016We extend a series of results due to Makienko, Dominguez and Sienra on the rigidity of some holomorphic dynamical systems with summable critical values to the setting of finite type maps. We also recover a shorter proof of a transversality theorem of ... More
Compactification and trees of spheres coversAug 09 2014We already saw in [A1] that the space of dynamically marked rational maps can be identified to a subspace of the space of covers between trees of spheres on which there is a notion of convergence that makes it sequentially compact. In the following we ... More
Rigidity-based approach to the boson peak in amorphous solids: from sphere packing to amorphous silicaJun 27 2008Glasses have a large excess of low-frequency vibrational modes in comparison with continuous elastic body, the so-called Boson Peak, which appears to correlate with several crucial properties of glasses, such as transport or fragility. I review recent ... More
The Singular Limit of a Chemotaxis-Growth System with General Initial DataSep 16 2009We study the singular limit of a system of partial differential equations which is a model for an aggregation of amoebae subjected to three effects: diffusion, growth and chemotaxis. The limit problem involves motion by mean curvature together with a ... More
Cohomologie equivariante des varietes de Bott-SamelsonJan 08 2002In this text, We compute the equivariant cohomology of Bott-Samelson varieties. Thanks to this computation, we give a new demonstration for the formulas proved by Sarah Billey for the equivariant cohomology of Schubert varieties.
Automatic structures for torus link groupsNov 07 2001A general result of Epstein and Thurston implies that all link groups are automatic, but the proof provides no explicit automaton. Here we show that the groups of all torus links are groups of fractions of so-called Garside monoids, i.e., roughly speaking, ... More
Correlations between vibrational entropy and dynamics in super-cooled liquidsNov 20 2009Jun 20 2010A relation between vibrational entropy and particles mean square displacement is derived in super-cooled liquids, assuming that the main effect of temperature changes is to rescale the vibrational spectrum. Deviations from this relation, in particular ... More
Scaling of phononic transport with connectivity in amorphous solidsSep 16 2009Mar 01 2010The effect of coordination on transport is investigated theoretically using random networks of springs as model systems. An effective medium approximation is made to compute the density of states of the vibrational modes, their energy diffusivity (a spectral ... More
Hardcore dimer aspects of the SU(2) Singlet wavefunctionJun 17 2007Apr 17 2008We demonstrate that any SU(2) singlet wavefunction can be characterized by a set of Valence Bond occupation numbers, testing dimer presence/vacancy on pairs of sites. This genuine quantum property of singlet states (i) shows that SU(2) singlets share ... More
On the Rigidity of Amorphous SolidsDec 07 2005We poorly understand the properties of amorphous systems at small length scales, where a continuous elastic description breaks down. This is apparent when one considers their vibrational and transport properties, or the way forces propagate in these solids. ... More
Cohomologie et $K$-theorie equivariantes des tours de Bott et des varietes de drapeaux. Application au calcul de SchubertNov 06 2003We determine the structure of the equivariant cohomology and $K$-theory of Bott towers. By restriction, we obtain similar results for Bott-Samelson varieties. This results allow us to describe more precisely the equivariant cohomology and $K$-theory of ... More
Generation, motion and thickness of transition layers for a nonlocal Allen-Cahn equationJun 07 2009We investigate the behavior, as a small parameter tends to zero, of a nonlocal Allen-Cahn equation. Given a rather general initial data, we perform a rigorous analysis of both the generation and the motion of interface, and obtain a new estimate for its ... More
NP-completeness of Certain Sub-classes of the Syndrome Decoding ProblemDec 02 2009The problem of Syndrome Decoding was proven to be NP-complete in 1978 and, since then, quite a few cryptographic applications have had their security rely on the (provable) difficulty of solving some instances of it. However, in most cases, the instances ... More
Garside monoids vs divisibility monoidsJul 05 2007Divisibility monoids (resp. Garside monoids) are a natural algebraic generalization of Mazurkiewicz trace monoids (resp. spherical Artin monoids), namely monoids in which the distributivity of the underlying lattices (resp. the existence of common multiples) ... More
Bounding the number of $(σ,ρ)$-dominating sets in trees, forests and graphs of bounded pathwidthApr 05 2019The notion of $(\sigma,\rho)$-dominating set generalizes many notions including dominating set, induced matching, perfect codes or independent sets. Bounds on the maximal number of such (maximal, minimal) sets were established for different $\sigma$ and ... More
Concentration inequalities for $s$-concave measures of dilations of Borel sets and applicationsJul 01 2008We prove a sharp inequality conjectured by Bobkov on the measure of dilations of Borel sets in $\mathbb{R}^n$ by a $s$-concave probability. Our result gives a common generalization of an inequality of Nazarov, Sodin and Volberg and a concentration inequality ... More
Explicit Presentations for the Dual Braid MonoidsNov 27 2001Birman, Ko and Lee have introduced a new monoid ${\cal B}^{*}_{n}$--with an explicit presentation--whose group of fractions is the $n$-strand braid group ${\cal B}_{n}$. Building on a new approach by Digne, Michel and himself, Bessis has defined a {\it ... More
The far infra-red SEDs of main sequence and starburst galaxiesJul 19 2016We compare observed far infra-red/sub-millimetre (FIR/sub-mm) galaxy spectral energy distributions (SEDs) of massive galaxies ($M_{\star}\gtrsim10^{10}$ $h^{-1}$M$_{\odot}$) derived through a stacking analysis with predictions from a new model of galaxy ... More
Finite transducers for divisibility monoidsJan 13 2006Divisibility monoids are a natural lattice-theoretical generalization of Mazurkiewicz trace monoids, namely monoids in which the distributivity of the involved divisibility lattices is kept as an hypothesis, but the relations between the generators are ... More
The slope equations: a universal relationship between local structure and glass transition temperatureMay 12 1998In this article, we present a universal relationship between the glass transition temperature $T_g$ and the local glass structure. The derivation of the simplest expression of this relationship and some comparisons with experimental $T_g$ values have ... More
Structure of densified germanium dioxideOct 28 2003Classical molecular dynamics simulations are used to study the structure of densified germanium dioxide ($GeO_2$). It is found that the coordination number of germanium changes with increasing density (pressure) while pressure released systems do not ... More
Nucleation model for the description of glass formationSep 16 1998We present in this letter a model of glass formation using energy barriers and a crystal nucleation process. We then analyze the corresponding dynamical equation in the vicinity of the stationary solutions. The occurence of a pure amorphous solution (i.e. ... More
Optimal model selection for density estimation of stationary data under various mixing conditionsNov 08 2009Dec 13 2011We propose a block-resampling penalization method for marginal density estimation with nonnecessary independent observations. When the data are $\beta$ or $\tau$-mixing, the selected estimator satisfies oracle inequalities with leading constant asymptotically ... More
On the dependence of the avalanche angle on the granular layer thicknessJul 31 2008A layer of sand of thickness h flows down a rough surface if the inclination is larger than some threshold value theta which decreases with h. A tentative microscopic model for the dependence of theta with h is proposed for rigid frictional grains, based ... More
Theory and Practice of Triangle Problems in Very Large (Sparse (Power-Law)) GraphsSep 20 2006Finding, counting and/or listing triangles (three vertices with three edges) in large graphs are natural fundamental problems, which received recently much attention because of their importance in complex network analysis. We provide here a detailed state ... More
Reading escaping trees from Hubbard trees in SnMar 09 2015We prove that the parameter space of monic centered cubic polynomials with a critical point of exact period n=4 is connected. The techniques developed for this proof work for every n and provide an interesting relation between escaping trees of DeMarco-McMullen ... More
Caractérisations des espaces projectifs et des quadriquesSep 07 2010Sep 10 2010In this paper we prove the following result : if the p-th tensor power of the tangent bundle of a smooth projective variety contains the p-th power of an ample line bundle, then the variety is isomorphic either to the projective space or to a smooth quadric ... More
Adaptive density estimation for stationary processesSep 05 2009We propose an algorithm to estimate the common density $s$ of a stationary process $X_1,...,X_n$. We suppose that the process is either $\beta$ or $\tau$-mixing. We provide a model selection procedure based on a generalization of Mallows' $C_p$ and we ... More
Determinants of finite-dimensional algebrasDec 12 2007Dec 13 2007To each associative unitary finite-dimensional algebra over a normal base, we associative a canonical multiplicative function called its determinant. We give various properties of this construction, as well as applications to the topology of the moduli ... More
Composantes connexes et irréductibles en famillesDec 14 2009Feb 18 2010For an algebraic stack $\sX$ flat and of finite presentation over a scheme $S$, we introduce various notions of {\em relative connected components} and {\em relative irreducible components}. The main distinction between these notions is whether we require ... More
Effective models of group schemesApr 21 2009Oct 07 2009Let $R$ be a discrete valuation ring with fraction field $K$ and $X$ a flat $R$-scheme. Given a faithful action of a $K$-group scheme $G_K$ over the generic fibre $X_K$, we study models $G$ of $G_K$ acting on $X$. In various situations, we prove that ... More
The stack of Potts curves and its fibre at a prime of wild ramificationJan 30 2002May 18 2003In this article we study the modular properties of a family of cyclic coverings of P^1 of degree N, in all odd characteristics. We compute the moduli space of the corresponding algebraic stack over Z[1/2], as well as the Picard groups over algebraically ... More
Approximability of dynamical systems between trees of spheresAug 09 2014We study sequences of analytic conjugacy classes of rational maps which diverge in moduli space. In particular, we are interested in the notion of rescaling limits introduced by Jan Kiwi. In the continuity of [A1] we recall the notion of dynamical covers ... More
A Chevalley formula in equivariant $K$-theoryMar 09 2006The aim of this paper is to give a recursive formula to multiply a line bundle with the structure sheaf of a schubert variety in the equivariant $K$-theory of a flag variety.
Paysage Systolique Des Surfaces Hyperboliques Compactes De Caracteristique -1Aug 01 2005We determine optimal inequalities for the systole of all hyperbolic compact surfaces of caracteristic -1. First, we study the geometry and topology of these surfaces. Then, we describe the action of modular groups on Teichm\"{u}ller spaces. Finaly, we ... More
Linking rigidity transitions with enthalpic changes at the glass transition and the fragility of glass-forming liquidsMar 13 2008A low temperature Monte Carlo dynamics of a Keating like oscillator model is used to study the relationship between the nature of glasses from the viewpoint of rigidity, and the strong-fragile behaviour of glass-forming liquids. The model shows that a ... More
Intermediate phase in molecular networks and solid electrolytesJun 24 2002There is growing evidence that electronic and molecular networks present some common universal properties, among which the existence of a self-organized intermediate phase. In glasses, the latter is revealed by the reversibility window obtained from complex ... More
K-theorie equivariante des varietes de Bott-Samelson. Application a la structure multiplicative de la K-theorie equivariante des varietes de drapeauxDec 07 2004We construct a basis of the equivariant $K$-theory of Bott towers, and we describe precisely the multiplicative structure of these algebras. We deduce similar results for Bott-Samelson varieties. Thanks to the link between flag varieties and Bott-Samelson ... More
Dual Garside structure and reducibility of braidsMay 18 2011Feb 22 2012Benardete, Gutierrez and Nitecki showed an important result which relates the geometrical properties of a braid, as a homeomorphism of the punctured disk, to its algebraic Garside-theoretical properties. Namely, they showed that if a braid sends a curve ... More
Effective model of a finite group actionJan 26 2006Let $R$ be a discrete valuation ring with fraction field $K$. Let $X$ be a flat $R$-scheme of finite type and $G$ a finite flat group scheme acting on $X$ so that $G\_K$ is faithful on the generic fibre $X\_K$. We prove that there is an effective model ... More
A note on group actions on algebraic stacksMay 16 2003We give the basic definitions of group actions on (algebraic) stacks, and prove the existence of fixed points and quotients as (algebraic) stacks.
Tomography of the Cosmic Dawn and Reionization Eras with Multiple TracersMar 28 2019The Cosmic Dawn and Reionization epochs remain a fundamental but challenging frontier of astrophysics and cosmology. We advocate a large-scale, multi-tracer approach to develop a comprehensive understanding of the physics that led to the formation and ... More
The impact of clustering and angular resolution on far-infrared and millimeter continuum observationsMar 26 2017Aug 24 2017Follow-up observations at high-angular resolution of submillimeter galaxies showed that the single-dish sources are comprised of a blend of several galaxies. Consequently, number counts derived from low and high angular resolution observations are in ... More
On the Rationality of EscalationApr 29 2010Escalation is a typical feature of infinite games. Therefore tools conceived for studying infinite mathematical structures, namely those deriving from coinduction are essential. Here we use coinduction, or backward coinduction (to show its connection ... More
On the Rationality of EscalationDec 09 2009Dec 15 2011Escalation is a typical feature of infinite games. Therefore tools conceived for studying infinite mathematical structures, namely those deriving from coinduction are essential. Here we use coinduction, or backward coinduction (to show its connection ... More
Convex isoperimetric sets in the Heisenberg groupJul 26 2006We characterize convex isoperimetric sets in the Heisenberg group endowed with horizontal perimeter. We first prove Sobolev regularity for a certain class of vector fields in the plane with bounded variation, related to the curvature equations. Then, ... More
Efficient spike-sorting of multi-state neurons using inter-spike intervals informationMay 27 2005We demonstrate the efficacy of a new spike-sorting method based on a Markov Chain Monte Carlo (MCMC) algorithm by applying it to real data recorded from Purkinje cells (PCs) in young rat cerebellar slices. This algorithm is unique in its capability to ... More
Combinatorics of the three-parameter PASEP partition functionDec 07 2009Jan 19 2011We consider a partially asymmetric exclusion process (PASEP) on a finite number of sites with open and directed boundary conditions. Its partition function was calculated by Blythe, Evans, Colaiori, and Essler. It is known to be a generating function ... More
Generation of interface for an Allen-Cahn equation with nonlinear diffusionSep 18 2009In this note, we consider a nonlinear diffusion equation with a bistable reaction term arising in population dynamics. Given a rather general initial data, we investigate its behavior for small times as the reaction coefficient tends to infinity: we prove ... More
Convergence of a mass conserving Allen-Cahn equation whose Lagrange multiplier is nonlocal and localMar 14 2013We consider the mass conserving Allen-Cahn equation proposed in \cite{Bra-Bre}: the Lagrange multiplier which ensures the conservation of the mass contains not only nonlocal but also local effects (in contrast with \cite{Che-Hil-Log}). As a parameter ... More
On the existence of solutions to the planar exterior Navier Stokes systemJul 16 2012We consider the stationary incompressible Navier Stokes equation in the exterior of a disk B with non-zero Dirichlet boundary conditions on the disk and zero boundary conditions at infinity. We prove the existence of solutions for an open set of boundary ... More
Source-specific routingMar 03 2014Mar 30 2015Source-specific routing (not to be confused with source routing) is a routing technique where routing decisions depend on both the source and the destination address of a packet. Source-specific routing solves some difficult problems related to multihoming, ... More
Lifting the Gribov ambiguity in Yang-Mills theoriesFeb 15 2012May 06 2012We propose a new one-parameter family of Landau gauges for Yang-Mills theories which can be formulated by means of functional integral methods and are thus well suited for analytic calculations, but which are free of Gribov ambiguities and avoid the Neuberger ... More
Convergence to a propagating front in a degenerate Fisher-KPP equation with advectionApr 19 2011We consider a Fisher-KPP equation with density-dependent diffusion and advection, arising from a chemotaxis-growth model. We study its behavior as a small parameter, related to the thickness of a diffuse interface, tends to zero. We analyze, for small ... More
Phase behavior and structure of colloidal bowl-shaped particles: simulationsJul 01 2010We study the phase behavior of bowl-shaped particles using computer simulations. These particles were found experimentally to form a meta-stable worm-like fluid phase in which the bowl-shaped particles have a strong tendency to stack on top of each other ... More
Covert Secret Key Generation with an Active WardenJan 07 2019We investigate the problem of covert and secret key generation over a discrete memoryless channel model with one way public discussion and in presence of an active warden who can arbitrarily vary its channel and tamper with the main channel when an information ... More
Matrix Product representation of the stationary state of the open Zero Range ProcessMar 22 2018Many one-dimensional lattice particle models with open boundaries, like the paradigmatic Asymmetric Simple Exclusion Process (ASEP), have their stationary states represented in the form of a matrix product, with matrices that do not explicitly depend ... More
A tractable Multi-Partitions ClusteringJan 22 2018In the framework of model-based clustering, a model allowing several latent class variables is proposed. This model assumes that the distribution of the observed data can be factorized into several independent blocks of variables. Each block is assumed ... More
Field induced stationary state for an accelerated tracer in a bathMar 30 2012Aug 24 2012Our interest goes to the behavior of a tracer particle, accelerated by a constant and uniform external field, when the energy injected by the field is redistributed through collision to a bath of unaccelerated particles. A non equilibrium steady state ... More
On the Prym variety of genus 3 covers of genus 1 curvesDec 21 2016Mar 15 2018Given a generic degree-2 cover of a genus 1 curve D by a non hyperelliptic genus 3 curve C over a field k of characteristic different from 2, we produce an explicit genus 2 curve X such that Jac(C) is isogenous to the product of Jac(D) and Jac(X). This ... More
Irreducibility of the set of cubic polynomials with one periodic critical pointNov 28 2016The space of monic centered cubic polynomials with marked critical points is isomorphic to C^2. For each n>0, the locus Sn formed by all polynomials with a specified critical point periodic of exact period n forms an affine algebraic set. We prove that ... More
Normal modes analysis of the microscopic dynamics in hard discsApr 15 2008May 09 2008We estimate numerically the normal modes of the free energy in a glass of hard discs. We observe that, near the glass transition or after a rapid quench deep in the glass phase, the density of states (i) is characteristic of a marginally stable structure, ... More
Linear operators with wild dynamicsApr 10 2012If $X$ is a separable infinite dimensional Banach space, we construct a bounded and linear operator $R$ on $X$ such that $$ A_R=\{x \in X, \|R^tx\| \rightarrow \infty\} $$ is not dense and has non empty interior with the additional property that $R$ can ... More
Person re-identification across different datasets with multi-task learningJul 25 2018This paper presents an approach to tackle the re-identification problem. This is a challenging problem due to the large variation of pose, illumination or camera view. More and more datasets are available to train machine learning models for person re-identification. ... More
On the dependent conjunction and implicationJun 20 2016We give a theoretical model of conjunctions $E\wedge F$ and implications $E\implies F$ where $F$ is meaningful only when $E$ is true, a situation which is very often encountered in everyday mathematics, and which was already formalized by several type ... More
On the phases of PoloniumAug 03 2009The thermodynamical properties of the main phases of metallic polonium are examined using Density Functional Theory. The exceptional nature of the solid-solid phase transition of $\alpha$ to $\beta$ Po is underlined: it induces a lowering in symmetry, ... More
A q-enumeration of alternating permutationsJul 06 2009A classical result of Euler states that the tangent numbers are an alternating sum of Eulerian numbers. A dual result of Roselle states that the secant numbers can be obtained by a signed enumeration of derangements. We show that both identities can be ... More
Infrared propagators of Yang-Mills theory from perturbation theoryApr 09 2010We show that the correlation functions of ghosts and gluons for the pure Yang-Mills theory in Landau gauge can be accurately reproduced for all momenta by a one-loop calculation. The key point is to use a massive extension of the Faddeev-Popov action. ... More
Fast algorithmic Nielsen-Thurston classification of four-strand braidsApr 01 2010Jan 27 2012We give an algorithm which decides the Nielsen-Thurston type of a given four-strand braid. The complexity of our algorithm is quadratic with respect to word length. The proof of its validity is based on a result which states that for a reducible 4-braid ... More
Coding Distributive Lattices with Edge Firing GamesOct 19 2001In this note, we show that any distributive lattice is isomorphic to the set of reachable configurations of an Edge Firing Game. Together with the result of James Propp, saying that the set of reachable configurations of any Edge Firing Game is always ... More
Sharp interface limit of the Fisher-KPP equationOct 12 2009We investigate the singular limit, as $\ep \to 0$, of the Fisher equation $\partial_t u=\ep \Delta u + \ep ^{-1}u(1-u)$ in the whole space. We consider initial data with compact support plus, possibly, perturbations very small as $\Vert x \Vert \to \infty$. ... More
Fast generation of random connected graphs with prescribed degreesFeb 22 2005We address here the problem of generating random graphs uniformly from the set of simple connected graphs having a prescribed degree sequence. Our goal is to provide an algorithm designed for practical use both because of its ability to generate very ... More
A generic tool to generate a lexicon for NLP from Lexicon-Grammar tablesMay 31 2010Lexicon-Grammar tables constitute a large-coverage syntactic lexicon but they cannot be directly used in Natural Language Processing (NLP) applications because they sometimes rely on implicit information. In this paper, we introduce LGExtract, a generic ... More
Open-source platforms for fast room acoustic simulations in complex structuresNov 13 2018This article presents new numerical simulation tools, respectively developed in Matlab and Blender softwares. Available in open-source under the GPL 3.0 license, it uses a ray-tracing/image-sources hybrid method to calculate the room acoustics for large ... More
Anderson Acceleration for Reinforcement LearningSep 25 2018Anderson acceleration is an old and simple method for accelerating the computation of a fixed point. However, as far as we know and quite surprisingly, it has never been applied to dynamic programming or reinforcement learning. In this paper, we explain ... More
Microscopic processes controlling the Herschel-Bulkley exponentAug 01 2017Jan 15 2018The flow curve of various yield stress materials is singular as the strain rate vanishes, and can be characterized by the so-called Herschel-Bulkley exponent $n=1/\beta$. A mean-field approximation due to Hebraud and Lequeux (HL) assumes mechanical noise ... More
Local regularity for parabolic nonlocal operatorsMar 09 2012May 20 2013Weak solutions to parabolic integro-differential operators of order $\alpha \in (\alpha_0, 2)$ are studied. Local a priori estimates of H\"older norms and a weak Harnack inequality are proved. These results are robust with respect to $\alpha \nearrow ... More