Results for "Philippe Chartier"

total 5419took 0.11s
Uniformly accurate time-splitting methods for the semiclassical Schrödinger equationPart 2 : Numerical analysis of the linear caseJan 19 2016This article is second part of a twofold paper, devoted to the construction of numerical methods which remain insensitive to the smallness of the semiclassical parameter for the Schr{\"o}dinger equation in the semiclassical limit. Here, we specifically ... More
An averaging technique for transport equationsSep 30 2016In this paper, we develop a new strategy aimed at obtaining high-order asymptotic models for transport equations with highly-oscillatory solutions. The technique relies upon averaging theory for ordinary differential equations, in particular normal form ... More
Analysis of a time-dependent problem of mixed migration and population dynamicsDec 07 2015In this work, we consider a system of differential equations modeling the dynamics of some populations of preys and predators, moving in space according to rapidly oscillating time-dependent transport terms, and interacting with each other through a Lotka-Volterra ... More
Averaging of highly-oscillatory transport equationsSep 30 2016Nov 14 2016In this paper, we develop a new strategy aimed at obtaining high-order asymptotic models for transport equations with highly-oscillatory solutions. The technique relies upon recent developments averaging theory for ordinary differential equations, in ... More
Uniformly accurate time-splitting methods for the semiclassical Schrödinger equation Part 1 : Construction of the schemes and simulationsMay 11 2016This article is devoted to the construction of new numerical methods for the semiclassical Schr\"odinger equation. A phase-amplitude reformulation of the equation is described where the Planck constant epsilon is not a singular parameter. This allows ... More
Continuous changes of variables and the Magnus expansionJul 11 2019In this paper, we are concerned with a formulation of Magnus and Floquet-Magnus expansions for general nonlinear differential equations. To this aim, we introduce suitable continuous variable transformations generated by operators. As an application of ... More
A new class of uniformly accurate numerical schemes for highly oscillatory evolution equationsDec 18 2017We introduce a new methodology to design uniformly accurate methods for oscillatory evolution equations. The targeted models are envisaged in a wide spectrum of regimes, from non-stiff to highly-oscillatory. Thanks to an averaging transformation, the ... More
Solving highly-oscillatory NLS with SAM: numerical efficiency and geometric propertiesAug 06 2013In this paper, we present the Stroboscopic Averaging Method (SAM), recently introduced in [7,8,10,12], which aims at numerically solving highly-oscillatory differential equations. More specifically, we first apply SAM to the Schr\"odinger equation on ... More
Uniformly accurate methods for three dimensional Vlasov equations under strong magnetic field with varying directionJul 10 2019In this paper, we consider the three dimensional Vlasov equation with an inhomogeneous, varying direction, strong magnetic field. Whenever the magnetic field has constant intensity, the oscillations generated by the stiff term are periodic. The homogenized ... More
Uniformly accurate numerical schemes for highly oscillatory Klein-Gordon and nonlinear Schrödinger equationsAug 02 2013This work is devoted to the numerical simulation of nonlinear Schr\"odinger and Klein-Gordon equations. We present a general strategy to construct numerical schemes which are uniformly accurate with respect to the oscillation frequency. This is a stronger ... More
Uniformly accurate methods for Vlasov equations with non-homogeneous strong magnetic fieldFeb 08 2018In this paper, we consider the numerical solution of highly-oscillatory Vlasov and Vlasov-Poisson equations with non-homogeneous magnetic field. Designed in the spirit of recent uniformly accurate methods, our schemes remain insensitive to the stiffness ... More
A new class of uniformly accurate numerical schemes for highly oscillatory evolution equationsDec 18 2017Jan 10 2019We introduce a new methodology to design uniformly accurate methods for oscillatory evolution equations. The targeted models are envisaged in a wide spectrum of regimes, from non-stiff to highly-oscillatory. Thanks to an averaging transformation, the ... More
Highly-oscillatory problems with time-dependent vanishing frequencyJul 20 2018In the analysis of highly-oscillatory evolution problems, it is commonly assumed that a single frequency is present and that it is either constant or, at least, bounded from below by a strictly positive constant uniformly in time. Allowing for the possibility ... More
Optimized high-order splitting methods for some classes of parabolic equationsFeb 08 2011Dec 07 2011We are concerned with the numerical solution obtained by splitting methods of certain parabolic partial differential equations. Splitting schemes of order higher than two with real coefficients necessarily involve negative coefficients. It has been demonstrated ... More
Medical image computing and computer-aided medical interventions applied to soft tissues. Work in progress in urologyDec 13 2007Until recently, Computer-Aided Medical Interventions (CAMI) and Medical Robotics have focused on rigid and non deformable anatomical structures. Nowadays, special attention is paid to soft tissues, raising complex issues due to their mobility and deformation. ... More
Irradiated Carbon Nanostructures as Nanoscopic Pressure CellsSep 21 2010Nov 23 2010High-dose irradiation of nanostructures consisting of multiple graphene shells, such as spherical 'carbon onions' (CO) or cylindrical multi-walled carbon nanotubes (MWNT), induces shell shrinkage by bond reconstruction around irradiation-induced defects. ... More
A multiplicative property of quantum flag minorsDec 19 2001We study multiplicative properties of the (quantum) dual canonical basis B* associated to a semi-simple complex Lie group G. We provide a subset D of B* such that the following property holds : if two elements b, b' in B* q-commute and if one of these ... More
Gif Lectures on Cosmic AccelerationDec 18 2009Jan 06 2010These lecture notes cover some of the theoretical topics associated with cosmic acceleration. Plausible explanations to cosmic acceleration include dark energy, modified gravity and a violation of the Copernican principle. Each of these possibilities ... More
Harmonic functions on the real hyperbolic ball I : Boundary values and atomic decomposition of Hardy spacesFeb 08 1999We study harmonic functions for the Laplace-Beltrami operator on the real hyperbolic ball. We obtain necessary and sufficient conditions for this functions and their normal derivatives to have a boundary distribution.In doing so, we put forward different ... More
Disambiguating with Controlled DisjunctionsOct 14 1997In this paper, we propose a disambiguating technique called controlled disjunctions. This extension of the so-called named disjunctions relies on the relations existing between feature values (covariation, control, etc.). We show that controlled disjunctions ... More
Weighted Paley-Wiener spaces and mountain chain axioms: a detailed expositionMay 01 2013The present work reviews the second half of Lyubarskii and Seip's paper, Weighted Paley--Wiener Spaces. Axioms defining a larger class of de Branges spaces are abstracted, allowing us to state and prove their results at a higher level of generality.
Spin dynamics in Cuprates and its relation to superconductivitySep 25 2000The relevance of magnetism for the mechanism responsible for high-temperature superconductivity remains an open and still interesting issue. The observation by inelastic neutron scattering of strong antiferromagnetic dynamical correlations in superconducting ... More
SIMBOL-X, an X-ray telescope for the 0.5-70 keV rangeOct 10 2002SIMBOL-X is a high energy "mini" satellite class mission that is proposed by a European collaboration for a launch in 2009. SIMBOL-X is making use of a classical X-ray mirror, of ~600 cm2 maximum effective area, with a 30 m focal length in order to cover ... More
Spectroscopy of Gauge Theories Based on Exceptional Lie GroupsJul 18 2001Jul 25 2001We generate by computer a basis of invariants for the fundamental representations of the exceptional Lie groups E(6) and E(7), up to degree 18. We discuss the relevance of this calculation for the study of supersymmetric gauge theories, and revisit the ... More
Finite Number of States, de Sitter Space and Quantum Groups at Roots of UnityJun 26 2003Jul 20 2003This paper explores the use of a deformation by a root of unity as a tool to build models with a finite number of states for applications to quantum gravity. The initial motivation for this work was cosmological breaking of supersymmetry. We explain why ... More
Raman Spectrometry, a Unique Tool to Analyze and Classify Ancient Ceramics and GlassesJan 15 2007Raman micro/macro-spectroscopy allows for a non-destructive remote analysis: body and glaze, crystalline and amorphous phases can be identified, including the nanosized pigments colouring the glaze. Last generation instruments are portable which allows ... More
The quantum Poincare group from quantum group contractionSep 18 1994We propose a contraction of the de Sitter quantum group leading to the quantum Poincare group in any dimensions. The method relies on the coaction of the de Sitter quantum group on a non--commutative space, and the deformation parameter $q$ is sent to ... More
The Herschel View of Star FormationSep 30 2013Recent studies of the nearest star-forming clouds of the Galaxy at submillimeter wavelengths with the Herschel Space Observatory have provided us with unprecedented images of the initial conditions and early phases of the star formation process. The Herschel ... More
Improved energy extrapolation with infinite projected entangled-pair states applied to the 2D Hubbard modelAug 17 2015May 10 2016An infinite projected entangled-pair state (iPEPS) is a variational tensor network ansatz for 2D wave functions in the thermodynamic limit where the accuracy can be systematically controlled by the bond dimension $D$. We show that for the doped Hubbard ... More
Cuspidal RobotsOct 13 2016This chapter is dedicated to the so-called cuspidal robots, i.e. those robots that can move from one inverse geometric solution to another without meeting a singular confuguration. This feature was discovered quite recently and has then been fascinating ... More
Estimation of the shift parameter in regression models with unknown distribution of the observationsDec 20 2013This paper is devoted to the estimation of the shift parameter in a semiparametric regression model when the distribution of the observation times is unknown. Hence, we propose to use a stochastic algorithm which takes into account the estimation of the ... More
Against all odds? Forming the planet of the HD196885 binaryMar 20 2011HD196885Ab is the most "extreme" planet-in-a-binary discovered to date, whose orbit places it at the limit for orbital stability. The presence of a planet in such a highly perturbed region poses a clear challenge to planet-formation scenarios. We investigate ... More
Logarithmic conformal invariance in the Abelian sandpile modelMar 18 2013We review the status of the two-dimensional Abelian sandpile model as a strong candidate to provide a lattice realization of logarithmic conformal invariance with central charge c=-2. Evidence supporting this view is collected from various aspects of ... More
Wind on the boundary for the Abelian sandpile modelJul 25 2007Jul 25 2007We continue our investigation of the two-dimensional Abelian sandpile model in terms of a logarithmic conformal field theory with central charge c=-2, by introducing two new boundary conditions. These have two unusual features: they carry an intrinsic ... More
Symmetric boundary conditions in boundary critical phenomenaApr 14 1999Jun 30 1999Conformally invariant boundary conditions for minimal models on a cylinder are classified by pairs of Lie algebras $(A,G)$ of ADE type. For each model, we consider the action of its (discrete) symmetry group on the boundary conditions. We find that the ... More
Automorphisms of the affine SU(3) fusion rulesJan 29 1993We classify the automorphisms of the (chiral) level-k affine SU(3) fusion rules, for any value of k, by looking for all permutations that commute with the modular matrices S and T. This can be done by using the arithmetic of the cyclotomic extensions ... More
Spin-1/2 frustrated antiferromagnet on a spatially anisotopic square lattice: contribution of exact diagonalizationsJul 04 2003Apr 07 2004The phase diagram of a spin-1/2 $J-J'-J_2$ model is investigated by means of exact diagonalizations on finite samples. This model is a generalization of the $J_1-J_2$ model on the square lattice with two different nearest-neighbor couplings $J,J'$ and ... More
From entangled codipterous coalgebras to coassociative manifoldsJan 09 2003We construct from coassociative coalgebras, bialgebras, Hopf algebras, new objects such as Poisson algebras, Leibniz algebras defined by J-L Loday and M. Ronco and explore the notion of coassociative manifolds.
Maximal eigenvalue and norm of the product of Toeplitz matrices. Study of a particular caseOct 29 2012In this paper we describe the asymptotic behaviour of the spectral norm of the product of two finite Toeplitz matrices as the matrix dimension goes to the infinity. These Toeplitz matrices are generated by positive functions with Fisher-Hartwig singularities ... More
High temperature Sherrington-Kirkpatrick model for general spinsOct 09 2002Francesco Guerra and Fabio Toninelli have developped a very powerful technique to study the high temperature behaviour of the Sherrington-Kirkpatrick mean field spin glass model. They show that this model is asymptoticaly comparable to a linear model. ... More
A Bayesian Variational Framework for Stochastic OptimizationMay 05 2019This work proposes a theoretical framework for stochastic optimization algorithms, based on a continuous Bayesian variational model for algorithms. Using techniques from stochastic control with asymmetric information, the solution to this variational ... More
A Bayesian Variational Framework for Stochastic OptimizationMay 05 2019May 08 2019This work proposes a theoretical framework for stochastic optimization algorithms, based on a continuous-time Bayesian variational model. Using techniques from stochastic control with asymmetric information, the solution to this variational problem is ... More
Free probability and combinatoricsApr 22 2003A combinatorial approach to free probability theory has been developped by Roland Speicher, based on the notion of noncrossing cumulants, a free analogue of the classical theory of cumulants in probability theory. We review this theory, and explain the ... More
Expression asymptotique des valeurs propres d'une matrice de Toeplitz à symbole réelDec 14 2015Sep 20 2017This work provides two results obtained as a consequence of an inversion formula for Toeplitz matrices with real symbol. First we obtain an asymptotic expression for the minimal eigenvalues of a Toeplitz matrix with a symbolwhich is periodic, even and ... More
Invariant hypersurfaces for derivations in positive characteristicFeb 15 2006Let $A$ be an integral $k$-algebra of finite type over an algebraically closed field $k$ of characteristic $p>0$. Given a collection ${\cal{D}}$ of $k$-derivations on $A$, that we interpret as algebraic vector fields on $X=Spec(A)$, we study the group ... More
Group actions, $k$-derivations and finite morphismsApr 06 2006Let $G$ be an affine algebraic group over an algebraically closed field $k$ of characteristic zero. In this paper, we consider finite $G$-equivariant morphisms $F:X\to Y$ of irreducible affine $G$-varieties. First we determine under which conditions on ... More
Computations of Nambu-Poisson cohomologiesJul 17 2000Mar 01 2001We try to generalize the Poisson cohomology of a 2-dimensional Poisson manifold to the n-vectors on a n-dimensional manifold. We define several cohomologies and we compute locally some of them, in the case of germs at 0 of n-vectors on a real or complex ... More
Rotational-tidal phasing of the binary neutron star waveformMay 04 2018Tidal forces cause inspiralling binary neutron stars to deform, leaving a measurable imprint on the gravitational waves they emit. The induced stellar multipoles are an added source of gravitational radiation and modify the orbital dynamics, producing ... More
Some deterministic structured population models which are limit of stochastic individual based modelsApr 13 2018The aim of this paper is to tackle part of the program set by Diekmann et al. in their seminal paper Diekmann et al. (2001). We quote "It remains to investigate whether, and in what sense, the nonlinear determin-istic model formulation is the limit of ... More
A remark on Gibbs-type measures for Hamiltonian PDESep 07 2017We find the optimal exponent of normalizability for certain Gibbs-type measures based on variants of Brownian motion which have appeared in the PDE literature, starting with an influential paper of Lebowitz, Rose and Speer (1988). We give a proof of a ... More
Semi-simple groups that are quasi-split over a tamely-ramified extensionJul 10 2017Let K be a discretly henselian field whose residue field is separably closed. Answering a question raised by G. Prasad, we show that a semisimple K-- group G is quasi-split if and only if it quasi--splits after a finite tamely ramified extension of K. ... More
L'idéal de Bernstein d'un arrangement libre d'hyperplans linéairesOct 06 2016Let $ V $ a vector space of dimension $n$. A family $ \{H_1, \ldots, H_p \} $ of vectorial hyperplans $V$ defines an arrangement $ {\cal A} $ of $ V $. For $ i \in \{ 1, \ldots, p \} $, let $ l_i $ be a linear form on $V$ with $H_i$ as kernel. We denote ... More
Six model categories for directed homotopyApr 08 2019We construct a q-model structure, a h-model structure and a m-model structure on multipointed $d$-spaces and on flows. The two q-model structures are combinatorial and coincide with the combinatorial model structures already known on these categories. ... More
Laplace copulas of multifactor gamma distributions are new generalized Farlie-Gumbel-Morgenstern copulasNov 22 2016This paper provides bifactor gamma distribution, trivariate gamma distribution and two copula families on [0, 1] n obtained from the Laplace transforms of the multivariate gamma distribution and the multi-factor gamma distribution given by [P ($\theta$)] ... More
Idéal de Bernstein d'un arrangement central générique d'hyperplansOct 06 2016Let $ V $ a vector space of dimension $n$. A $V$ family $ \{H_1, \ldots, H_p \} $ of vectorial hyperplanes being distinct two by two defines an arrangement $ {\cal A}_p = {\cal A} ( H_1, \ldots ,H_p ) $ of $ V $. For $ i \in \{ 1, \ldots, p \} $, let ... More
Towards a homotopy theory of process algebraJan 19 2007May 15 2008This paper proves that labelled flows are expressive enough to contain all process algebras which are a standard model for concurrency. More precisely, we construct the space of execution paths and of higher dimensional homotopies between them for every ... More
T-homotopy and refinement of observation (III) : Invariance of the branching and merging homologiesMay 16 2005Sep 20 2006This series explores a new notion of T-homotopy equivalence of flows. The new definition involves embeddings of finite bounded posets preserving the bottom and the top elements and the associated cofibrations of flows. In this third part, it is proved ... More
T-homotopy and refinement of observation (II) : Adding new T-homotopy equivalencesMay 16 2005Mar 26 2007This paper is the second part of a series of papers about a new notion of T-homotopy of flows. It is proved that the old definition of T-homotopy equivalence does not allow the identification of the directed segment with the 3-dimensional cube. This contradicts ... More
Concurrent Process up to Homotopy (II)Feb 24 2003One proves that the category of globular CW-complexes up to dihomotopy is equivalent to the category of flows up to weak dihomotopy. This theorem generalizes the classical theorem which states that the category of CW-complexes up to homotopy is equivalent ... More
A Convenient Category for The Homotopy Theory of ConcurrencyJan 25 2002May 03 2005Withdrawn paper because the results are published in math.AT/0308054 and math.AT/0308063.
T-homotopy and refinement of observation (IV) : Invariance of the underlying homotopy typeMay 16 2005Jun 06 2006This series explores a new notion of T-homotopy equivalence of flows. The new definition involves embeddings of finite bounded posets preserving the bottom and the top elements and the associated cofibrations of flows. In this fourth part, it is proved ... More
Rotation and magnetic activity evolution of Sun-like starsSep 21 2018Characterising the long-term evolution of magnetic activity on Sun-like stars is important not only for stellar physics but also for understanding the environment in which planets evolve. In the past decades, many photometric surveys of open clusters ... More
Towards a homotopy theory of higher dimensional transition systemsNov 03 2010Jan 30 2014We proved in a previous work that Cattani-Sassone's higher dimensional transition systems can be interpreted as a small-orthogonality class of a topological locally finitely presentable category of weak higher dimensional transition systems. In this paper, ... More
Homotopical equivalence of combinatorial and categorical semantics of process algebraNov 08 2007Nov 12 2007It is possible to translate a modified version of K. Worytkiewicz's combinatorial semantics of CCS (Milner's Calculus of Communicating Systems) in terms of labelled precubical sets into a categorical semantics of CCS in terms of labelled flows using a ... More
The geometry of cubical and regular transition systemsMay 20 2014Sep 29 2015There exist cubical transition systems containing cubes having an arbitrarily large number of faces. A regular transition system is a cubical transition system such that each cube has the good number of faces. The categorical and homotopical results of ... More
A note on rational surfaces in projective four-spaceMay 24 1999It is proved that a smooth rational surface in projective four-space, which is ruled by cubics or quartics has degree at most 12. It is also proved that a smooth rational surface in projective four-space which is the image of Fn by a linear system with ... More
Sur le spectre des longueurs des groupes de trianglesJan 29 2009Feb 25 2009We describe in this report the beginning of the length spectra of fuchsian triangular groups
Asymptotics of the solitary waves for the generalised Kadomtsev-Petviashvili equationsFeb 21 2009We investigate the asymptotic behaviour of the localised solitary waves for the generalised Kadomtsev-Petviashvili equations. In particular, we compute their first order asymptotics in any dimension $N \geq 2$.
Homotopy invariants of higher dimensional categories and concurrency in computer scienceFeb 26 1999Feb 27 2000The strict globular $\omega$-categories formalize the execution paths of a parallel automaton and the homotopies between them. One associates to such (and any) $\omega$-category $\C$ three homology theories. The first one is called the globular homology. ... More
Directed algebraic topology and higher dimensional transition systemMar 25 2009Jun 18 2010Cattani-Sassone's notion of higher dimensional transition system is interpreted as a small-orthogonality class of a locally finitely presentable topological category of weak higher dimensional transition systems. In particular, the higher dimensional ... More
Isotypic Decomposition of the Cohomology and Factorization of the Zeta Functions of Dwork HypersurfacesDec 10 2009The aim of this article is to illustrate, on the example of Dwork hypersurfaces, how the study of the representation of a finite group of automorphisms of a hypersurface in its etale cohomology allows to factor its zeta function.
Generalised Mertens and Brauer-Siegel TheoremsMar 20 2007In this article, we prove a generalisation of the Mertens theorem for prime numbers to number fields and algebraic varieties over finite fields, paying attention to the genus of the field (or the Betti numbers of the variety), in order to make it tend ... More
On the Zeta Function of a Family of QuinticsJul 21 2009In this article, we give a proof of the link between the zeta function of two families of hypergeometric curves and the zeta function of a family of quintics that was observed numerically by Candelas, de la Ossa, and Rodriguez Villegas. The method we ... More
L-algebras, triplicial-algebras, within an equivalence of categories motivated by graphsSep 21 2007Apr 16 2008In a previous work, we gave a coalgebraic framework of directed graphs equipped with weights (or probability vectors) in terms of (Markov) L-coalgebras. They are K-vector spaces equipped with two co-operations, \Delta_M, \tilde{\Delta}_M verifying, (\tilde{\Delta}_M ... More
Fedosov Star-Products and 1-Differentiable DeformationsSep 07 1998We show that every star product on a symplectic manifold defines uniquely a 1-differentiable deformation of the Poisson bracket. Explicit formulas are given. As a corollary we can identify the characteristic class of any star product as a part of its ... More
Lectures on Screened Modified GravityNov 22 2012The acceleration of the expansion of the Universe has led to the construction of Dark Energy models where a light scalar field may have a range reaching up to cosmological scales. Screening mechanisms allow these models to evade the tight gravitational ... More
Lorentz Invariance Violation in Modified GravityFeb 03 2012May 10 2012We consider an environmentally dependent violation of Lorentz invariance in scalar-tensor models of modified gravity where General Relativity is retrieved locally thanks to a screening mechanism. We find that fermions have a modified dispersion relation ... More
SIMBOL-X, a new generation X-ray telescope for the 0.5-70 keV rangeSep 04 2002SIMBOL-X is a high energy "mini" satellite class mission that is proposed by a French-Italian-English collaboration for a launch in 2009. SIMBOL-X is making use of a classical X-ray mirror, of ~ 600 cm2 maximum effective area, with a 30 m focal length ... More
Quantum Determinism for Free Vector Bosons in 3 DimensionsJun 24 2001We apply 't Hooft's deterministic quantum mechanics approach to free vector bosons in three dimensions and check Lorentz invariance. This approach does not work for the conformal group, for free bosons in two dimensions. This presents a technical difficulty ... More
Polymerisation Degree and Raman Identification of Ancient Glasses used for Jewellery, Ceramics Enamels and MosaicsJan 17 2007We demonstrate the utility of Raman spectroscopy as a technique for the identification of ancient glasses and enamel coatings of ceramics. As for any silicate glasses, the addition of network modifiers breaks the Si-O linkages and modifies the degree ... More
Introduction to spectral methodsSep 06 2006This proceeding is intended to be a first introduction to spectral methods. It is written around some simple problems that are solved explicitly and in details and that aim at demonstrating the power of those methods. The mathematical foundation of the ... More
Morrey spaces and classification of global solutions for a supercritical semilinear heat equation in $R^n$Apr 06 2016Apr 13 2016We prove the boundedness of global classical solutions for the semilinear heat equation $u_t-\Delta u= |u|^{p-1}u$ in the whole space $R^n$, with $n\ge 3$ and supercritical power $p>(n+2)/(n-2)$. This is proved {\rmb without any radial symmetry or sign ... More
Spatio-temporal dynamics of an active, polar, viscoelastic ringFeb 17 2014Constitutive equations for a one-dimensional, active, polar, viscoelastic liquid are derived by treating the strain field as a slow hydrodynamic variable. Taking into account the couplings between strain and polarity allowed by symmetry, the hydrodynamics ... More
Fractal Fluctuations in Human Walking: Comparison between Auditory and Visually Guided SteppingSep 07 2015Feb 18 2016In human locomotion, sensorimotor synchronization of gait consists of the coordination of stepping with rhythmic auditory cues (auditory cueing, AC). AC changes the long-range correlations among consecutive strides (fractal dynamics) into anti-correlations. ... More
Combinatorics of past-similarity in higher dimensional transition systemsJul 26 2016The key notion to understand the left determined Olschok model category of star-shaped Cattani-Sassone transition systems is past-similarity. Two states are past-similar if they have homotopic pasts. An object is fibrant if and only if the set of transitions ... More
Rigidity of actions on presymplectic manifoldsJan 06 2016We prove the rigidity of Hamiltonian or presymplectic actions of a compact semisimple Lie algebra on a presymplectic manifold of constant rank in the local and global case. The proof uses an abstract normal form theorem we had stated in a previous work, ... More
Jones matrices of perfectly conducting metallic polarizersApr 18 2014We deduce from Monomode Modal Method the analytical expressions of transmission and reflexion Jones matrices of an infinitely conducting metallic screen periodically pierced by subwavelength holes. The study is restricted to normal incidence and to the ... More
Polynomial Depth, Highness and Lowness for EFeb 10 2016We study the relations between the notions of highness, lowness and logical depth in the setting of complexity theory. We introduce a new notion of polynomial depth based on time bounded Kolmogorov complexity. We show our polynomial depth notion satisfies ... More
Henri Poincaré and his "model" of hyperbolic geometryFeb 03 2016The aim of the talk is to trace how and when Henri Poincar\'e used non-Euclidean geometries (NEG) in his mathematical and philosophical works, with a particular attention to the genesis and the description of his model. We begin by a short presentation ... More
On the length of fully commutative elementsNov 27 2015In a Coxeter group $W$, an element is fully commutative if any two of its reduced expressions can be linked by a series of commutation of adjacent letters. These elements have particularly nice combinatorial properties, and also index a basis of the generalized ... More
Generalized Zeta function representation of groups and 2-dimensional Topological Yang-Mills theory: The example of GL(2, F_q) and PGL(2, F_q)Dec 11 2015We recall the relation between Zeta function representation of groups and two-dimensional topological Yang-Mills theory through Mednikh formula. We prove various generalisations of Mednikh formulas and define generalization of Zeta functions representations ... More
On the construction of integrable dilute ADE modelsApr 14 1992We give an integrable extension of the lattice models recently considered by I.Kostov in his study of strings in discrete space. These models are IRF models with spin variables living in any connected graph, the vertex model underlying these models is ... More
Vertical structure of debris discsJun 30 2009The vertical thickness of debris discs is often used as a measure of these systems' dynamical excitation and as clues to the presence of hidden massive perturbers such as planetary embryos. However, this argument could be flawed because the observed dust ... More
Kramers-Wannier dualities via symmetriesApr 28 2005Nov 23 2005Kramers-Wannier dualities in lattice models are intimately connected with symmetries. We show that they can be found directly and explicitly from the symmetry transformations of the boundary states in the underlying conformal field theory. Intriguingly ... More
A c=-2 boundary changing operator for the Abelian sandpileMar 12 2002Oct 02 2002We consider the unoriented two-dimensional Abelian sandpile model on the half-plane with open and closed boundary conditions. We show that the operator effecting the change from closed to open, or from open to closed, is a boundary primary field of weight ... More
Un théoréme de Nakai-Moishezon pour certaines classes de type (1,1)Nov 10 1998Let $X$ be a smooth compact projective variety over $\mathbb C$. Let $H^2(\pi_1(X),\mathbb R)^{1,1}$ be the intersection of $H^{1,1}(X,{\mathbb R})$ with the image of the map $H^2(\pi_1(X),{\mathbb R})\to H^2(X)$ induced by the classifying map $X\to B\pi_1(X)$. ... More
Random generation of combinatorial structures: Boltzmann samplers and beyondDec 21 2011The Boltzmann model for the random generation of "decomposable" combinatorial structures is a set of techniques that allows for efficient random sampling algorithms for a large class of families of discrete objects. The usual requirement of sampling uniformly ... More
"Disproof of Bell's Theorem" : more criticsJul 15 2007Aug 17 2007In a series of recent papers (quant-ph/0703179, quant-ph/0703244, arXiv:0707.1333) Joy Christian claims to have "disproved Bell's theorem". Though his work is certainly intellectually stimulating, we argue below that his main claim is unwarranted.
Contextual objectivity and quantum holismJan 01 2003Jan 03 2003In our effort to restate a "realistic" approach to quantum mechanics, that would fully acknowledge that local realism is untenable, we add a few more questions and answers to the list presented in quant-ph/0203131. We also suggest to replace the very ... More