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Results for "Raphaël Pestourie"

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Sideways adiabaticity: Beyond ray optics for slowly varying metasurfacesJun 14 2018Nov 14 2018Optical metasurfaces (subwavelength-patterned surfaces typically described by variable effective surface impedances) are typically modeled by an approximation akin to ray optics: the reflection or transmission of an incident wave at each point of the ... More
Inverse design of large-area metasurfacesAug 13 2018Dec 14 2018We present a computational framework for efficient optimization-based "inverse design" of large-area "metasurfaces" (subwavelength-patterned surfaces) for applications such as multi-wavelength and multi-angle optimizations, and demultiplexers. To optimize ... More
Topology optimization of freeform large-area metasurfacesFeb 08 2019We demonstrate optimization of optical metasurfaces over $10^5$--$10^6$ degrees of freedom in two and three dimensions, 100--1000+ wavelengths ($\lambda$) in diameter, with 100+ parameters per $\lambda^2$. In particular, we show how topology optimization, ... More
Similarity results for operators of class $C_0$ and the algebra $H^\infty(T)$Aug 16 2012May 22 2014Given two multiplicity-free operators $T_1$ and $T_2$ of class $C_0$ having the same finite Blaschke product as minimal function, the operator algebras $H^\infty(T_1)$ and $H^\infty(T_2)$ are isomorphic and $T_1$ is similar to $T_2$. We find conditions ... More
A Lagrangian approach for the compressible Navier-Stokes equationsJan 30 2012Sep 25 2014Here we investigate the Cauchy problem for the barotropic Navier-Stokes equations in R^n, in the critical Besov spaces setting. We improve recent results as regards the uniqueness condition: initial velocities in critical Besov spaces with (not too) \emph{negative} ... More
Rationality of cycles over function fields of $SL_1(A)$-torsorsSep 06 2014In this note we prove a result comparing rationality of algebraic cycles over the function field of a $SL_1(A)$-torsor for a central simple algebra $A$ and over the base field.
Noise-stability and central limit theorems for effective resistance of random electric networksJun 18 2012Mar 15 2016We investigate the (generalized) Walsh decomposition of point-to-point effective resistances on countable random electric networks with i.i.d. resistances. We show that it is concentrated on low levels, and thus point-to-point effective resistances are ... More
Arbitrary threshold widths for monotone symmetric propertiesJan 06 2006We investigate the threshold widths of some symmetric properties which range asymptotically between 1/\sqrt{n} and 1/(log n). These properties are built using a combination of failure sets arising from reliability theory. This combination of sets is simply ... More
On the semi-classical analysis of Schrödinger operators with purely imaginary electric potentials in a bounded domainMay 23 2014In this paper, we describe the leftmost eigenvalue of the non-selfadjoint operator $\mathcal{A}_h = -h^2\Delta+iV(x)$ with Dirichlet boundary conditions on a smooth bounded domain $\Omega\subset\mathbb{R}^n\,$, as $h\rightarrow0\,$. $V$ is assumed to ... More
Spectral projections of the complex cubic oscillatorOct 17 2013We prove the spectral instability of the complex cubic oscillator $-\frac{d^2}{dx^2}+ix^3+i\alpha x$ for non-negative values of the parameter $\alpha$, by getting the exponential growth rate of $\|\Pi_n(\alpha)\|$, where $\Pi_n(\alpha)$ is the spectral ... More
Picard group of the forms of the affine line and of the additive groupOct 07 2016We obtain an explicit upper bound on the torsion of the Picard group of the forms of the affine line and of the additive group, and a sufficient condition for this Picard group to be non trivial. We also give examples of non trivial forms of the affine ... More
Modell zur Entstehung eines Rings aus Dunkler Materie in der MilchstraßenebeneOct 29 2008Jan 15 2010Both the distribution of hydrogen and the rotation curve of the Milky Way indicate the existence of a ring of Cold Dark Matter in the galactic plane with a radius of 14 kiloparsecs around the galactic centre. Using a semianalytical model, the formation ... More
Symmetric correspondences on quadricsNov 14 2016We prove a result comparing the rationality of some elementary algebraic cycles introduced by Alexander Vishik, defined on orthogonal grassmannians, with the rationality of some algebraic cycles defined on fiber products of the corresponding quadric.
Quasisimilarity of invariant subspaces for $C_0$ operators with multiplicity twoSep 17 2011May 22 2014For an operator $T$ of class $C_0$ with multiplicity two, we show that the quasisimilarity class of an invariant subspace $M$ is determined by the quasisimilarity classes of the restriction $T|M$ and of the compression $T_{M^\perp}$. We also provide a ... More
Soliton resolution for equivariant wave maps to the sphereMay 23 2013We consider finite energy corotationnal wave maps with target manifold $\m S^2$. We prove that for a sequence of times, they decompose as a sum of decoupled harmonic maps in the light cone, and a smooth wave map (in the blow case) or a linear scattering ... More
Khovanov-Rozansky homology and 2-braid groupsMar 22 2012Khovanov has given a construction of the Khovanov-Rozansky link invariants (categorifying the HOMFLYPT invariant) using Hochschild cohomology of 2-braid groups. We give a direct proof that his construction does give link invariants. We show more generally ... More
A Twisted Fourth Moment of Dirichlet L-functionsNov 29 2016Dec 05 2016We evaluate some twisted fourth moment of Dirichlet $L$-functions at the central point s=1/2 and for prime moduli q. The principal tool is a careful analysis of a shifted convolution problem involving the divisor function using spectral theory of automorphic ... More
On the well-posedness of the incompressible density-dependent Euler equations in the $L^p$ frameworkJul 23 2009The present paper is devoted to the study of the well-posedness issue for the density-dependent Euler equations in the whole space. We establish local-in-time results for the Cauchy problem pertaining to data in the Besov spaces embedded in the set of ... More
Fourier analysis methods for the compressible Navier-Stokes equationsJul 09 2015In the last three decades, Fourier analysis methods have known a growing importance in the study of linear and nonlinear PDE's. In particular, techniques based on Littlewood-Paley decomposition and paradifferential calculus have proved to be very efficient ... More
Similarity results for operators of class C_0Apr 01 2011Oct 05 2011If T is a multiplicity-free contraction of class C_0 with minimal function m_T, then it is quasisimilar to the Jordan block S(m_T). In case m_T is a Blaschke product with simple roots forming a Carleson sequence, we show that the relation between T and ... More
A Twisted Fourth Moment of Dirichlet L-functionsNov 29 2016We evaluate some twisted fourth moment of Dirichlet $L$-functions at the central point s=1/2 and for prime moduli q. The principal tool is a careful analysis of a shifted convolution problem involving the divisor function using spectral theory of automorphic ... More
Scaling limit of dynamical percolation on critical Erdös-Rényi random graphsOct 25 2017Jun 22 2018Consider a critical Erd\"os-R\'enyi random graph: $n$ is the number of vertices, each one of the $\binom{n}{2}$ possible edges is kept in the graph independently from the others with probability $n^{-1}+\lambda n^{-4/3}$, $\lambda$ being a fixed real ... More
Around rationality of integral cyclesMar 12 2012In this article we prove a result comparing rationality of integral algebraic cycles over the function field of a quadric and over the base field. This is an integral version of the result known for coefficients modulo 2. Those results have already been ... More
On quantitative noise stability and influences for discrete and continuous modelsJan 28 2014Nov 12 2014In [K-K], Keller and Kindler proved a quantitative version of the famous Benjamini - Kalai-Schramm Theorem on noise sensitiviy of Boolean funtions. The result was extented to the continuous Gaussian setting in [K-M-S2] by means of a Central Limit Theorem ... More
Remarks on the lifespan of the solutions to some models of incompressible fluid mechanicsJan 30 2012We give lower bounds for the lifespan of a solution to the inviscid Boussinesq system. In dimension two, we point out that it tends to infinity when the initial (relative) temperature tends to zero. This is, to the best of our knowledge, the first result ... More
The quasispecies regime for the simple genetic algorithm with roulette-wheel selectionJun 30 2015Dec 03 2015We introduce a new parameter to discuss the behavior of a genetic algorithm. This parameter is the mean number of exact copies of the best fit chromosomes from one generation to the next. We argue that the genetic algorithm should operate efficiently ... More
A lower bound on the two-arms exponent for critical percolation on the latticeJun 13 2013Oct 29 2015We consider the standard site percolation model on the $d$-dimensional lattice. A direct consequence of the proof of the uniqueness of the infinite cluster of Aizenman, Kesten and Newman [Comm. Math. Phys. 111 (1987) 505-531] is that the two-arms exponent ... More
Parallelizing Stream with FutureMay 19 2013Stream is re-interpreted in terms of a Lazy monad. Future is substituted for Lazy in the obtained construct, resulting in possible parallelization of any algorithm expressible as a Stream computation. The principle is tested against two example algorithms. ... More
Critical population and error threshold on the sharp peak landscape for the Wright-Fisher modelJul 03 2012Jun 19 2015We pursue the task of developing a finite population counterpart to Eigen's model. We consider the classical Wright-Fisher model describing the evolution of a population of size $m$ of chromosomes of length $\ell$ over an alphabet of cardinality $\kappa$. ... More
Unitary equivalence and similarity to Jordan models for weak contractions of class $C_0$Jun 14 2013May 22 2014We obtain results on the unitary equivalence of weak contractions of class $C_0$ to their Jordan models under an assumption on their commutants. In particular, our work addresses the case of arbitrary finite multiplicity. The main tool is the theory of ... More
On the unilateral shift as a Hilbert module over the disc algebraFeb 25 2013May 22 2014We study the unilateral shift (of arbitrary countable multiplicity) as a Hilbert module over the disc algebra and the associated extension groups. In relation with the problem of determining whether this module is projective, we consider a special class ... More
Threshold for monotone symmetric properties through a logarithmic Sobolev inequalityNov 24 2005Nov 20 2006Threshold phenomena are investigated using a general approach, following Talagrand [Ann. Probab. 22 (1994) 1576--1587] and Friedgut and Kalai [Proc. Amer. Math. Soc. 12 (1999) 1017--1054]. The general upper bound for the threshold width of symmetric monotone ... More
Automizers as extended reflection groupsOct 21 2010Brou\'e, Malle and Michel have shown that the automizer of an abelian Sylow p-subgroup in a finite simple Chevalley group is an irreducible complex reflection group, for p not too small and different from the defining characteristic. The aim is this note ... More
Spectral instability for even non-selfadjoint anharmonic oscillatorsJan 22 2013Oct 17 2013We study the instability of the spectrum for a class of non-selfadjoint anharmonic oscillators, estimating the behavior of the instability indices (i. e. the norm of spectral projections) associated with the large eigenvalues of these oscillators. We ... More
The quasispecies regime for the simple genetic algorithm with ranking selectionMar 21 2014We study the simple genetic algorithm with a ranking selection mechanism (linear ranking or tournament). We denote by $\ell$ the length of the chromosomes, by $m$ the population size, by $p_C$ the crossover probability and by $p_M$ the mutation probability. ... More
Quasiaffine orbits of invariant subspaces for uniform Jordan operatorsAug 27 2011May 22 2014We consider the problem of classification of invariant subspaces for the class of uniform Jordan operators. We show that given two invariant subspaces $M_1$ and $M_2$ of a uniform Jordan operator $T=S(\theta)\oplus S(\theta)\oplus \ldots$, the subspace ... More
Completely bounded isomorphisms of operator algebras and similarity to complete isometriesJan 03 2014May 22 2014A well-known theorem of Paulsen says that if $\mathcal{A}$ is a unital operator algebra and $\phi:\mathcal{A}\to B(\mathcal{H})$ is a unital completely bounded homomorphism, then $\phi$ is similar to a completely contractive map $\phi'$. Motivated by ... More
Critical control of a genetic algorithmMay 19 2010Based on speculations coming from statistical mechanics and the conjectured existence of critical states, I propose a simple heuristic in order to control the mutation probability and the population size of a genetic algorithm.
Spectral and homological properties of Hilbert modules over the disc algebraJul 19 2013May 22 2014We study general Hilbert modules over the disc algebra and exhibit necessary spectral conditions for the vanishing of certain associated extension groups. In particular, this sheds some light on the problem of identifying the projective Hilbert modules. ... More
Critical population and error threshold on the sharp peak landscape for a Moran modelMay 15 2012Oct 23 2012The goal of this work is to propose a finite population counterpart to Eigen's model, which incorporates stochastic effects. We consider a Moran model describing the evolution of a population of size $m$ of chromosomes of length $\ell$ over an alphabet ... More
$J$-invariant of hermitian formsFeb 12 2016Oct 01 2016We develop the version of the $J$-invariant for hermitian forms in a similar way Alexander Vishik did it for quadratic forms. This discrete invariant contains informations about rationality of algebraic cycles on the maximal unitary grassmannian associated ... More
Network of BanditsFeb 11 2016Oct 11 2016The distribution of machine learning tasks on the user's devices offers several advantages for application purposes: scalability, reduction of deployment costs and privacy. We propose a basic brick, Distributed Median Elimination, which can be used to ... More
Spectral instability of some non-selfadjoint anharmonic oscillatorsJan 22 2013The purpose of this Note is to highlight the spectral instability of some non-selfadjoint differential operators, by studying the growth rate of the norms of the spectral projections $\Pi_n$ associated with their eigenvalues. More precisely, we are concerned ... More
Picard group of the forms of the affine line and of the additive groupOct 07 2016Nov 21 2016We obtain an explicit upper bound on the torsion of the Picard group of the forms of the affine line and their regular completions. We also obtain a sufficient condition for the Picard group of the forms of the affine line to be non trivial and we give ... More
The travel time in a finite box in supercritical Bernoulli percolationJul 11 2013We consider the standard site percolation model on the three dimensional cubic lattice. Starting solely with the hypothesis that $\theta(p)>0$, we prove that, for any $\alpha>0$, there exists $\kappa>0$ such that, with probability larger than $1-1/n^\alpha$, ... More
Geometrically-protected reversibility in hydrodynamic Loschmidt-echo experimentsJul 07 2014We demonstrate an archetypal Loschmidt-echo experiment involving thousands of droplets which interact in a reversible fashion via a viscous fluid. Firstly, we show that, unlike equilibrium systems, periodically driven microfluidic emulsions self-organize ... More
Convergence of a stochastic particle approximation for fractional scalar conservation lawsJun 21 2010We give a probabilistic numerical method for solving a partial differential equation with fractional diffusion and nonlinear drift. The probabilistic interpretation of this equation uses a system of particles driven by L\'evy alpha-stable processes and ... More
Endoscopie et conjecture raffinée de Gan-Gross-Prasad pour les groupes unitairesDec 05 2012Mar 29 2014Under endoscopic assumptions about $L$-packets of unitary groups, we prove the local Gan-Gross-Prasad conjecture for tempered representations of unitary groups over $p$-adic fields. Roughly, this conjecture says that branching laws for $U(n-1)\subset ... More
Construction of a multi-soliton blow-up solution to the semilinear wave equation in one space dimensionOct 11 2011Apr 24 2012We consider the semilinear wave equation with power nonlinearity in one space dimension. Given a blow-up solution with a characteristic point, we refine the blow-up behavior first derived by Merle and Zaag. We also refine the geometry of the blow-up set ... More
Lower large deviations for the maximal flow through a domain of $\mathbb{R}^d$ in first passage percolationJul 31 2009We consider the standard first passage percolation model in the rescaled graph $\mathbb{Z}^d/n$ for $d\geq 2$, and a domain $\Omega$ of boundary $\Gamma$ in $\mathbb{R}^d$. Let $\Gamma^1$ and $\Gamma^2$ be two disjoint open subsets of $\Gamma$, representing ... More
On the irreducibility of Deligne-Lusztig varietiesJan 16 2006Apr 12 2006Let $G$ be a connected reductive algebraic group defined over an algebraic closure of a finite field and let $F : G \to G$ be an endomorphism such that $F^d$ is a Frobenius endomorphism for some $d \geq 1$. Let $P$ be a parabolic subgroup of $G$ admitting ... More
The incompressible limit in $L^p$ type critical spacesSep 25 2014This paper aims at justifying the low Mach number convergence to the incompressible Navier-Stokes equations for viscous compressible flows in the ill-prepared data case. The fluid domain is either the whole space, or the torus. A number of works have ... More
Towards an ultra efficient kinetic scheme Part II: The high order caseDec 02 2012In a recent paper we presented a new ultra efficient numerical method for solving kinetic equations of the Boltzmann type (G. Dimarco, R. Loubere, Towards an ultra efficient kinetic scheme. Part I: basics on the 689 BGK equation, J. Comp. Phys., (2013), ... More
Weak shape theorem in first passage percolation with infinite passage timesApr 17 2014Nov 20 2014We consider the model of i.i.d. first passage percolation on $\mathbb{Z}^d$ : we associate with each edge $e$ of the graph a passage time $t(e)$ taking values in $[0,+\infty]$, such that $\mathbb{P}[t(e)<+\infty] >p_c(d)$. Equivalently, we consider a ... More
A local trace formula for the Gan-Gross-Prasad conjecture for unitary groups: the archimedean caseJun 04 2015Dec 21 2015In this paper, we prove, following earlier work of Waldspurger ([Wa1], [Wa4]), a sort of local relative trace formula which is related to the local Gan-Gross-Prasad conjecture for unitary groups over a local field $F$ of characteristic zero. As a consequence, ... More
On the well-posedness of the full compressible Navier-Stokes system in critical Besov spacesJul 17 2014We are concerned with the Cauchy problem of the full compressible Navier-Stokes equations satisfied by viscous and heat conducting fluids in $\mathbb{R}^n.$ We focus on the so-called critical Besov regularity framework. In this setting, it is natural ... More
The distribution of the quasispecies for a Moran model on the sharp peak landscapeDec 10 2013We consider the Moran model on the sharp peak landscape, in the asymptotic regime studied in [3], where a quasispecies is formed. We find explicitly the distribution of this quasispecies.
Monotonic cocyclesOct 02 2013We develop a "local theory" of multidimensional quasiperiodic $\SL(2,\R)$ cocycles which are not homotopic to a constant. It describes a $C^1$-open neighborhood of cocycles of rotations and applies irrespective of arithmetic conditions on the frequency, ... More
Universal large deviations for Kac polynomialsJul 08 2016We prove the universality of the large deviations principle for the empirical measures of zeros of random polynomials whose coefficients are i.i.d. random variables possessing a density with respect to the Lebesgue measure on C, R or R + , under the assumption ... More
Intermittency in spherical Couette dynamosApr 23 2013We investigate dynamo action in three-dimensional numerical simulations of turbulent spherical Couette flows. Close to the onset of dynamo action, the magnetic field exhibits an intermittent behavior, characterized by a series of short bursts of the magnetic ... More
Lower large deviations for the maximal flow through tilted cylinders in two-dimensional first passage percolationDec 18 2009Equip the edges of the lattice $\mathbb{Z}^2$ with i.i.d. random capacities. A law of large numbers is known for the maximal flow crossing a rectangle in $\mathbb{R}^2$ when the side lengths of the rectangle go to infinity. We prove that the lower large ... More
Lower large deviations and laws of large numbers for maximal flows through a box in first passage percolationJan 07 2008Jul 03 2009We consider the standard first passage percolation model in $\mathbb{Z}^d$ for $d\geq 2$. We are interested in two quantities, the maximal flow $\tau$ between the lower half and the upper half of the box, and the maximal flow $\phi$ between the top and ... More
Upper large deviations for the maximal flow through a domain of $\bolds{\mathbb{R}^d}$ in first passage percolationJul 31 2009Feb 17 2012We consider the standard first passage percolation model in the rescaled graph $\mathbb {Z}^d/n$ for $d\geq2$ and a domain $\Omega$ of boundary $\Gamma$ in $\mathbb {R}^d$. Let $\Gamma ^1$ and $\Gamma ^2$ be two disjoint open subsets of $\Gamma$ representing ... More
Nanomechanics of single keratin fibres: A Raman study of the alpha helix -> beta sheet transition and water effectJun 06 2007The use of micro-Raman spectroscopy, through chemical bond nano-scale probes, allows the changes in conformations (alpha helix -> beta sheet), chain orientation, disconnection of disulfide bonds (-20%) and the increase of intra and inter-chain distances ... More
Mixing HOL and Coq in Dedukti (Extended Abstract)Jul 31 2015We use Dedukti as a logical framework for interoperability. We use automated tools to translate different developments made in HOL and in Coq to Dedukti, and we combine them to prove new results. We illustrate our approach with a concrete example where ... More
A Lower Bound on the Relative Entropy with Respect to a Symmetric ProbabilityJul 03 2014Oct 20 2014Let $\rho$ and $\mu$ be two probability measures on $\mathbb{R}$ which are not the Dirac mass at $0$. We denote by $H(\mu|\rho)$ the relative entropy of $\mu$ with respect to $\rho$. We prove that, if $\rho$ is symmetric and $\mu$ has a finite first moment, ... More
Optimal time-decay estimates for the compressible navier-stokes equations in the critical l p frameworkMay 03 2016The global existence issue for the isentropic compressible Navier-Stokes equations in the critical regularity framework has been addressed in [7] more than fifteen years ago. However, whether (optimal) time-decay rates could be shown in general critical ... More
The Oberbeck-Boussinesq approximation in critical spacesApr 16 2013In this paper we study the validity of the so-called Oberbeck-Boussinesq approximation for compressible viscous perfect gases in the whole three-dimensional space. Both the cases of uids with positive heat conductivity and zero conductivity are considered. ... More
Topological quantization by controlled paths: application to Cooper pairs pumpsNov 05 2007When physical systems are tunable by three classical parameters, level degeneracies may occur at isolated points in parameter space. A topological singularity in the phase of the degenerate eigenvectors exists at these points. When a path encloses such ... More
A central limit theorem for the spatial Lambda Fleming-Viot process with selectionDec 18 2015Mar 09 2016We study the evolution of gene frequencies in a population living in $\mathbb{R}^d$, modelled by the spatial Lambda Fleming-Viot process with natural selection (Barton, Etheridge and Veber, 2010 and Etheridge, Veber and Yu, 2014). We suppose that the ... More
Strong mixing property for STIT tessellationsMay 08 2009May 17 2009The so-called STIT tessellations form the class of homogeneous (spatially stationary) tessellations of $\mathbb{R}^d$ which are stable under the nesting/iteration operation. In this paper, we establish the strong mixing property for these tessellations ... More
Light-Sound Interaction in Nanoscale Silicon WaveguidesMay 31 2016This thesis studies the interaction between near-infrared light and gigahertz sound in nanoscale silicon waveguides. Chapter 2 introduces photon-phonon coupling and its theoretical description, describing basic mechanisms and developing a quantum field ... More
Maximal stream and minimal cutset for first passage percolation through a domain of $\mathbb{R}^d$Jan 24 2012Mar 27 2014We consider the standard first passage percolation model in the rescaled graph $\mathbb{Z}^d/n$ for $d\geq2$ and a domain $\Omega$ of boundary $\Gamma$ in $\mathbb{R}^d$. Let $\Gamma ^1$ and $\Gamma ^2$ be two disjoint open subsets of $\Gamma$, representing ... More
Law of large numbers for the maximal flow through tilted cylinders in two-dimensional first passage percolationJul 29 2009Jan 14 2010Equip the edges of the lattice $\mathbb{Z}^2$ with i.i.d. random capacities. We prove a law of large numbers for the maximal flow crossing a rectangle in $\mathbb{R}^2$ when the side lengths of the rectangle go to infinity. The value of the limit depends ... More
Law of large numbers for the maximal flow through a domain of $\mathbb{R}^d$ in first passage percolationJul 31 2009We consider the standard first passage percolation model in the rescaled graph $\mathbb{Z}^d/n$ for $d\geq 2$, and a domain $\Omega$ of boundary $\Gamma$ in $\mathbb{R}^d$. Let $\Gamma^1$ and $\Gamma^2$ be two disjoint open subsets of $\Gamma$, representing ... More
Noncommutative Geometry and Conformal Geometry. III. Vafa-Witten Inequality and Poincaré DualityOct 23 2013Jan 11 2015This paper is the the third part of a series of paper whose aim is to use of the framework of \emph{twisted spectral triples} to study conformal geometry from a noncommutive geometric viewpoint. In this paper we reformulate the inequality of Vafa-Witten ... More
Limiting motion for the parabolic Ginzburg-Landau equation with infinite energy dataDec 01 2015We study a class of solutions to the parabolic Ginzburg-Landau equation in dimension 2 or higher, with ill-prepared infinite energy initial data. We show that, asymptotically, vorticity evolves according to motion by mean curvature in Brakke's weak formulation. ... More
Global Existence Results for the Anisotropic Boussinesq System in Dimension TwoSep 29 2008We study the global existence issue for the two-dimensional Boussinesq system with horizontal viscosity in only one equation. We first examine the case where the Navier-Stokes equation with no vertical viscosity is coupled with a transport equation. Second, ... More
Global persistence of geometrical structures for the boussinesq equation with no diffusionMar 24 2016Here we investigate the so-called temperature patch problem for the incompressible Boussinesq system with partial viscosity, in the whole space $\mathbb{R}^N$ $(N \geq 2)$, where the initial temperature is the characteristic function of some simply connected ... More
An Empirical Study of Cache-Oblivious Priority Queues and their Application to the Shortest Path ProblemFeb 07 2008In recent years the Cache-Oblivious model of external memory computation has provided an attractive theoretical basis for the analysis of algorithms on massive datasets. Much progress has been made in discovering algorithms that are asymptotically optimal ... More
Coxeter orbits and Brauer trees IIIApr 07 2012This article is the final one of a series of articles on certain blocks of modular representations of finite groups of Lie type and the associated geometry. We prove the conjecture of Brou\'e on derived equivalences induced by the complex of cohomology ... More
Affineness of Deligne-Lusztig varieties for minimal length elementsAug 09 2007Dec 03 2007We prove that the Deligne-Lusztig varieties associated to elements of the Weyl group which are of minimal length in their twisted class are affine. Our proof differs from the proof of He and Orlik-Rapoport and it is inspired by the case of regular elements, ... More
Scaling-sharp dispersive estimates for the Korteweg-de Vries groupApr 15 2008We prove weighted estimates on the linear KdV group, which are scaling sharp. This kind of estimates are in the spirit of that used to prove small data scattering for the generalized KdV equations.
Multi-travelling waves for the nonlinear klein-gordon equationDec 08 2016For the nonlinear Klein-Gordon equation in R 1+d , we prove the existence of multi-solitary waves made of any number N of decoupled bound states. This extends the work of C{\^o}te and Mu{\~n}oz (Forum Math. Sigma 2 (2014)) which was restricted to ground ... More
Diffusive limits for a barotropic model of radiative flowSep 09 2015Here we aim at justifying rigorously different types of physically relevant diffusive limits for radiative flows. For simplicity, we consider the barotropic situation, and adopt the so-called P1-approximation of the radiative transfer equation. In the ... More
Nucleation and growth for the Ising model in $d$ dimensions at very low temperaturesFeb 08 2011Dec 11 2013This work extends to dimension $d\geq3$ the main result of Dehghanpour and Schonmann. We consider the stochastic Ising model on ${\mathbb{Z}}^d$ evolving with the Metropolis dynamics under a fixed small positive magnetic field $h$ starting from the minus ... More
A short proof of the existence of supercuspidal representations for all reductive $p$-adic groupsApr 23 2015Dec 21 2015Let $G$ be a reductive $p$-adic group. We give a short proof of the fact that $G$ always admits supercuspidal complex representations. This result has already been established by A. Kret using the Deligne-Lusztig theory of representations of finite groups ... More
Quasispecies on class-dependent fitness landscapesApr 22 2015Apr 26 2016We study Eigen's quasispecies model in the asymptotic regime where the length of the genotypes goes to infinity and the mutation probability goes to 0. We give several explicit formulas for the stationary solutions of the limiting system of differential ... More
Bicovariograms and Euler characteristic I. Regular setsOct 02 2015Dec 31 2015We establish an expression of the Euler characteristic of a r-regular planar set in function of some variographic quantities. The usual C2 framework is relaxed to a C1,1 regularity assumption, generalising existing local formulas for the Euler characteristic. ... More
The well-posedness issue for the density-dependent Euler equations in endpoint Besov spacesMay 06 2013This work is the continuation of the recent paper \cite{D2} devoted to the density-dependent incompressible Euler equations. Here we concentrate on the well-posedness issue in Besov spaces of type $B^s_{\infty,r}$ embedded in the set of Lipschitz continuous ... More
Two-dimensional Kac-Rice formula. Application to shot noise processes excursionsJul 19 2016Given a deterministic function f:R^2->R atisfying suitable assump- tions, we show that for h smooth with compact support, the integral of the Euler characteristic of the excursion set of f above some level u against a test function h corresponds to the ... More
The Mirrors Model : Macroscopic Diffusion Without Noise or ChaosJun 15 2015Dec 21 2015We first clarify through classical examples the status of the laws of macroscopic physics as laws of large numbers. We next consider the mirrors model in a finite $d$-dimensional domain and connected to particles reservoirs at fixed chemical potentials. ... More
An Exponential Inequality for Symmetric Random VariablesJul 03 2014Oct 20 2014We prove the following exponential inequality: Let $n\geq 1$ and let $X_1,...,X_n$ be $n$ independent identically distributed symmetric real-valued random variables. For any $x,y>0$, we have \[\mathbb{P}\big({X_1+...+X_n}\geq x,\, {X_1^2+...+X_n^2}\leq ... More
Checking Zenon Modulo Proofs in DeduktiJul 31 2015Dedukti has been proposed as a universal proof checker. It is a logical framework based on the lambda Pi calculus modulo that is used as a backend to verify proofs coming from theorem provers, especially those implementing some form of rewriting. We present ... More
Polytopic uncertainty for linear systems: New and old complexity resultsOct 07 2013Feb 11 2014We survey the problem of deciding the stability or stabilizability of uncertain linear systems whose region of uncertainty is a polytope. This natural setting has applications in many fields of applied science, from Control Theory to Systems Engineering ... More
Coxeter orbits and modular representationsNov 30 2005Mar 15 2006We study the modular representations of finite groups of Lie type arising in the cohomology of certain quotients of Deligne-Lusztig varieties associated with Coxeter elements. These quotients are related to Gelfand-Graev representations and we present ... More
Observation of coherent back-scattering and its dynamics in a transverse 2D photonic disorder : from weak to strong localizationApr 28 2015May 02 2015We report the first observation of coherent back-scattering (CBS) of light in a transverse photonic disorder. The CBS peak is recorded in the far-field, at a fixed propagation time set by our crystal length, and displays a contrast approaching the ideal ... More
Converse Lyapunov theorems for discrete-time linear switching systems with regular switching sequencesOct 27 2014Nov 14 2014We present a stability analysis framework for the general class of discrete-time linear switching systems for which the switching sequences belong to a regular language. They admit arbitrary switching systems as special cases. Using recent results of ... More
On feedback stabilization of linear switched systems via switching signal controlJan 29 2016Aug 27 2016Motivated by recent applications in control theory, we study the feedback stabilizability of switched systems, where one is allowed to chose the switching signal as a function of $x(t)$ in order to stabilize the system. We propose new algorithms and analyze ... More
Residual finite dimensionality and representations of amenable operator algebrasDec 04 2016We consider a version of a famous open problem formulated by Kadison, asking whether bounded representations of operator algebras are automatically completely bounded. We investigate this question in the context of amenable operator algebras, and we provide ... More