Publications

2013

• Time-reversal in visco-elastic media.
  
  • Ammari Habib
  • Bretin Elie
  • Garnier Josselin
  • Wahab Abdul
  European Journal of Applied Mathematics, Cambridge University Press (CUP), 2013 (24), pp.565-600. In this paper, we consider the problem of reconstructing sources in a homogeneous viscoelastic medium from wavefield measurements. We first present a modified time-reversal imaging algorithm based on a weighted Helmholtz decomposition and justify mathematically that it provides a better approximation than by simply time reversing the displacement field, where artifacts due to the coupling betwe en the pressure and shear waves appear. Then, we investigate the source inverse problem in an elastic attenuating medium. We provide a regularized time-reversal imagin g which corrects the attenuation effect at the first order. The results of this paper yie ld the fundamental tools for solving imaging problems in elastic media using cross correl ation techniques
• On the extinction of Continuous State Branching Processes with catastrophes
  
  • Bansaye Vincent
  • Pardo Millan Juan Carlos
  • Smadi Charline
  Electronic Journal of Probability, Institute of Mathematical Statistics (IMS), 2013, 18, pp.1-31. We consider continuous state branching processes (CSBP) with additional multiplicative jumps modeling dramatic events in a random environment. These jumps are described by a Lévy process with bounded variation paths. We construct a process of this class as the unique solution of a stochastic differential equation. The quenched branching property of the process allows us to derive quenched and annealed results and to observe new asymptotic behaviors. We characterize the Laplace exponent of the process as the solution of a backward ordinary differential equation and establish the probability of extinction. Restricting our attention to the critical and subcritical cases, we show that four regimes arise for the speed of extinction, as in the case of branching processes in random environment in discrete time and space. The proofs are based on the precise asymptotic behavior of exponential functionals of Lévy processes. Finally, we apply these results to a cell infection model and determine the mean speed of propagation of the infection. (10.1214/EJP.v18-2774)
  DOI : 10.1214/EJP.v18-2774
• Aircraft classification with a low resolution infrared sensor
  
  • Lefebvre Sidonie
  • Allassonniere Sidonie
  • Jakubowicz Jérémie
  • Lasne Thomas
  • Moulines Éric
  Machine Vision and Applications, Springer Verlag, 2013, 24 (1), pp.175-186. Existing computer simulations of aircraft infrared signature (IRS) do not account for dispersion induced by uncertainty on input parameters, such as aircraft aspect angles and meteorological conditions. As a result, they are of little use to quantify the detection performance of IR optronic systems: in this case, the scenario encompasses a lot of possible situations that must indeed be considered, but cannot be individually simulated. In this paper, we focus on low resolution infrared sensors and we propose a methodological approach for predicting simulated IRS dispersion of an aircraft, and performing a classification of different aircraft on the resulting set of low resolution infrared images. It is based on a quasi-Monte Carlo survey of the code output dispersion, and on a maximum likelihood classification taking advantage of Bayesian dense deformable template models estimation. This method is illustrated in a typical scenario, i.e., a daylight air-to-ground full-frontal attack by a generic combat aircraft flying at low altitude, over a database of 30,000 simulated aircraft images. Assuming a spatially white noise background model, classification performance is very promising, and appears to be more accurate than more classical state of the art techniques (such as kernel-based support vector classifiers). (10.1007/s00138-012-0437-1)
  DOI : 10.1007/s00138-012-0437-1
• Daphnias: from the individual based model to the large population equation
  
  • Metz J.A.J.
  • Tran Viet Chi
  Journal of Mathematical Biology, Springer, 2013, 66 (4-5), pp.915--933. The class of deterministic 'Daphnia' models treated by Diekmann et~al. (J Math Biol 61: 277--318, 2010) has a long history going back to Nisbet and Gurney (Theor Pop Biol 23: 114--135, 1983) and Diekmann et~al. (Nieuw Archief voor Wiskunde 4: 82--109, 1984). In this note, we formulate the individual based models (IBM) supposedly underlying those deterministic models. The models treat the interaction between a general size-structured consumer population ('Daphnia') and an unstructured resource ('algae'). The discrete, size and age-structured Daphnia population changes through births and deaths of its individuals and throught their aging and growth. The birth and death rates depend on the sizes of the individuals and on the concentration of the algae. The latter is supposed to be a continuous variable with a deterministic dynamics that depends on the Daphnia population. In this model setting we prove that when the Daphnia population is large, the stochastic differential equation describing the IBM can be approximated by the delay equation featured in (Diekmann et~al., l.c.). (10.1007/s00285-012-0619-5)
  DOI : 10.1007/s00285-012-0619-5
• On the robust superhedging of measurable claims
  
  • Possamaï Dylan
  • Royer Guillaume
  • Touzi Nizar
  Electronic Communications in Probability, Institute of Mathematical Statistics (IMS), 2013, 18 (95), pp.1-13. The problem of robust hedging requires to solve the problem of superhedging under a nondominated family of singular measures. Recent progress was achieved by van Handel, Neufeld, and Nutz. We show that the dual formulation of this problem is valid in a context suitable for martingale optimal transportation or, more generally, for optimal transportation under controlled stochastic dynamics (10.1214/ECP.v18-2739)
  DOI : 10.1214/ECP.v18-2739
• Actuator and sensor fault detection, isolation and identification in nonlinear dynamical systems, with an application to a waste water treatment plant
  
  • Methnani Salowa
  • Lafont Frédéric
  • Gauthier Jean-Paul
  • Damak Tarak
  • Toumi Ahmed
  , 2013. no abstract
• The Factorization method applied to cracks with impedance boundary conditions
  
  • Boukari Yosra
  • Haddar Houssem
  Inverse Problems and Imaging, AIMS American Institute of Mathematical Sciences, 2013, 7 (4). We use the Factorization method to retrieve the shape of cracks with impedance boundary conditions from farfields associated with incident plane waves at a fixed fre- quency. This work is an extension of the study initiated by Kirsch and Ritter [Inverse Problems, 16, pp. 89-105, 2000] where the case of sound soft cracks is considered. We address here the scalar problem and provide theoretical validation of the method when the impedance boundary conditions hold on both sides of the crack. We then deduce an inversion algorithm and present some validating numerical results in the case of simply and multiply connected cracks.
• Sparse Adaptive Parameterization of Variability in Image Ensembles
  
  • Durrleman Stanley
  • Allassonnière Stéphanie
  • Joshi S.
  International Journal of Computer Vision, Springer Verlag, 2013, 101 (1), pp.161-183. This paper introduces a new parameterization of diffeomorphic deformations for the characterization of the variability in image ensembles. Dense diffeomorphic deformations are built by interpolating the motion of a finite set of control points that forms a Hamiltonian flow of self-interacting particles. The proposed approach estimates a template image representative of a given image set, an optimal set of control points that focuses on the most variable parts of the image, and template-to-image registrations that quantify the variability within the image set. The method automatically selects the most relevant control points for the characterization of the image variability and estimates their optimal positions in the template domain. The optimization in position is done during the estimation of the deformations without adding any computational cost at each step of the gradient descent. The selection of the control points is done by adding a L 1 prior to the objective function, which is optimized using the FISTA algorithm. (10.1007/s11263-012-0556-1)
  DOI : 10.1007/s11263-012-0556-1
• Stabilization of persistently excited linear systems
  
  • Chitour Yacine
  • Mazanti Guilherme
  • Sigalotti Mario
  , 2013, pp.85-120. This chapter presents recent developments on the stabilization of persistently excited linear systems. The first section of the chapter deals with finite-dimensional systems and gives two main results on stabilization, concerning neutrally stable systems and systems whose eigenvalues all have non-positive real parts. It also presents a result stating the existence of persistently excited systems for which the pair (A, b) is controllable but that cannot be stabilized by means of a linear state feedback. The second section presents some results for infinite-dimensional systems to the case of systems defined by a linear operator A which generates a strongly continuous contraction semigroup, with applications to Schrödinger's equation and the wave equation. The final section discusses some problems that remain open, giving some preliminary results in certain cases. (10.1002/9781118639856.ch4)
  DOI : 10.1002/9781118639856.ch4
• Transmission eigenvalues
  
  • Cakoni Fioralba
  • Haddar Houssem
  Inverse Problems, IOP Publishing, 2013, 29 (10), pp.100201. In inverse scattering theory, transmission eigenvalues can be seen as the extension of the notion of resonant frequencies for impenetrable objects to the case of penetrable dielectrics. The transmission eigenvalue problem is a relatively late arrival to the spectral theory of partial differential equations. Its first appearance was in 1986 in a paper by Kirsch who was investigating the denseness of far-field patterns for scattering solutions of the Helmholtz equation or, in more modern terminology, the injectivity of the far-field operator [1]. The paper of Kirsch was soon followed by a more systematic study by Colton and Monk in the context of developing the dual space method for solving the inverse scattering problem for acoustic waves in an inhomogeneous medium [2]. In this paper they showed that for a spherically stratified media transmission eigenvalues existed and formed a discrete set. Numerical examples were also given showing that in principle transmission eigenvalues could be determined from the far-field data. This first period of interest in transmission eigenvalues was concluded with papers by Colton et al in 1989 [3] and Rynne and Sleeman in 1991 [4] showing that for an inhomogeneous medium (not necessarily spherically stratified) transmission eigenvalues, if they existed, formed a discrete set. For the next seventeen years transmission eigenvalues were ignored. This was mainly due to the fact that, with the introduction of various sampling methods to determine the shape of an inhomogeneous medium from far-field data, transmission eigenvalues were something to be avoided and hence the fact that transmission eigenvalues formed at most a discrete set was deemed to be sufficient. In addition, questions related to the existence of transmission eigenvalues or the structure of associated eigenvectors were recognized as being particularly difficult due to the nonlinearity of the eigenvalue problem and the special structure of the associated transmission eigenvalue problem. The need to answer these questions became important after a series of papers by Cakoni et al [5], and Cakoni et al [6] suggesting that these transmission eigenvalues could be used to obtain qualitative information about the material properties of the scattering object from far-field data. The first answer to the existence of transmission eigenvalues in the general case was given in 2008 when Päivärinta and Sylvester showed the existence of transmission eigenvalues for the index of refraction sufficiently large [7] followed in 2010 by the paper of Cakoni et al who removed the size restriction on the index of refraction [8]. More importantly, in the latter it was shown that transmission eigenvalues yielded qualitative information on the material properties of the scattering object and Cakoni et al established in [9] that transmission eigenvalues could be determined from the Tikhonov regularized solution of the far-field equation. Since the appearance of these papers there has been an explosion of interest in the transmission eigenvalue problem (we refer the reader to our recent survey paper [10] for a detailed account of the developments in this field up to 2012) and the papers in this special issue are representative of the myriad directions that this research has taken. Indeed, we are happy to see that many open theoretical and numerical questions raised in [10] have been answered (totally or partially) in the contributions of this special issue: the existence of transmission eigenvalues with minimal assumptions on the contrast, the numerical evaluation of transmission eigenvalues, the inverse spectral problem, applications to non-destructive testing, etc. In addition to these topics, many other new investigations and research directions have been proposed as we shall see in the brief content summary below. A number of papers in this special issue are concerned with the question of existence of transmission eigenvalues and the structure of the associated transmission eigenfunctions. The three papers by respectively Robbiano [11], Blasten and Päivärinta [12], and Lakshtanov and Vainberg [13] provide new complementary results on the existence of transmission eigenvalues for the scalar problem under weak assumptions on the (possibly complex valued) refractive index that mainly stipulates that the contrast does not change sign on the boundary. It is interesting here to see three different new methods to obtain these results. On the other hand, the paper by Bonnet-Ben Dhia and Chesnel [14] addresses the Fredholm properties of the interior transmission problem when the contrast changes sign on the boundary, exhibiting cases where this property fails. Using more standard approaches, the existence and structure of transmission eigenvalues are analyzed in the paper by Delbary [15] for the case of frequency dependent materials in the context of Maxwell's equations, whereas the paper by Vesalainen [16] initiates the study of the transmission eigenvalue problem in unbounded domains by considering the transmission eigenvalues for Schrödinger equation with non-compactly supported potential. The paper by Monk and Selgas [17] addresses the case where the dielectric is mounted on a perfect conductor and provides some numerical examples of the localization of associated eigenvalues using the linear sampling method. A series of papers then addresses the question of localization of transmission eigenvalues and the associated inverse spectral problem for spherically stratified media. More specifically, the paper by Colton and Leung [18] provides new results on complex transmission eigenvalues and a new proof for uniqueness of a solution to the inverse spectral problem, whereas the paper by Sylvester [19] provides sharp results on how to locate all the transmission eigenvalues associated with angular independent eigenfunctions when the index of refraction is constant. The paper by Gintides and Pallikarakis [20] investigates an iterative least square method to identify the spherically stratified index of refraction from transmission eigenvalues. On the characterization of transmission eigenvalues in terms of far-field measurements, a promising new result is obtained by Kirsch and Lechleiter [21] showing how one can identify the transmission eigenvalues using the eigenvalues of the scattering operator which are available in terms of measured scattering data. In the paper by Kleefeld [22], an accurate method for computing transmission eigenvalues based on a surface integral formulation of the interior transmission problem and numerical methods for nonlinear eigenvalue problems is proposed and numerically validated for the scalar problem in three dimensions. On the other hand, the paper by Sun and Xu [23] investigates the computation of transmission eigenvalues for Maxwell's equations using a standard iterative method associated with a variational formulation of the interior transmission problem with an emphasis on the effect of anisotropy on transmission eigenvalues. From the perspective of using transmission eigenvalues in non-destructive testing, the paper by Cakoni and Moskow [24] investigates the asymptotic behavior of transmission eigenvalues with respect to small inhomogeneities. The paper by Nakamura and Wang [25] investigates the linear sampling method for the time dependent heat equation and analyses the interior transmission problem associated with this equation. Finally, in the paper by Finch and Hickmann [26], the spectrum of the interior transmission problem is related to the unique determination of the acoustic properties of a body in thermoacoustic imaging. We hope that this collection of papers will stimulate further research in the rapidly growing area of transmission eigenvalues and inverse scattering theory. (10.1088/0266-5611/29/10/100201)
  DOI : 10.1088/0266-5611/29/10/100201
• Mathématiques: l'explosion continue
  
  • Anantharaman Nalini
  • de Bouard Anne
  • Lagoutière Frédéric
  • Gegout-Petit Anne
  • Ollivier Yann
  • Santambrogio Filippo
  • Bardet Jean-Marc
  , 2013, pp.1-180.
• Perron--Frobenius theorem for nonnegative multilinear forms and extensions
  
  • Friedland S.
  • Gaubert Stéphane
  • Han L.
  Linear Algebra and its Applications, Elsevier, 2013, 438 (2), pp.738-749. We prove an analog of Perron-Frobenius theorem for multilinear forms with nonnegative coefficients, and more generally, for polynomial maps with nonnegative coefficients. We determine the geometric convergence rate of the power algorithm to the unique normalized eigenvector. (10.1016/j.laa.2011.02.042)
  DOI : 10.1016/j.laa.2011.02.042
• On the class of graphs with strong mixing properties
  
  • Isaev Mikhail
  • Isaeva K.V
  Proceeding of MIPT, 2013, 5 (6), pp.44-54. We study three mixing properties of a graph: large algebraic connectivity, large Cheeger constant (isoperimetric number) and large spectral gap from 1 for the second largest eigenvalue of the transition probability matrix of the random walk on the graph. We prove equivalence of this properties (in some sense). We give estimates for the probability for a random graph to satisfy these properties. In addition, we present asymptotic formulas for the numbers of Eulerian orientations and Eulerian circuits in an undirected simple graph.
• Surface integral formulation of the interior transmission problem
  
  • Cossonnière Anne
  • Haddar Houssem
  Journal of Integral Equations and Applications, Rocky Mountain Mathematics Consortium, 2013, 25 (3), pp.341-376.. We consider a surface integral formulation of the so-called interior transmission problem that appears in the study of inverse scattering problems from dielectric inclusions. In the case where the magnetic permeability contrast is zero, the main originality of our approach consists in still using classical potentials for the Helmholtz equation but in weaker trace space solutions. One major outcome of this study is to establish Fredholm properties of the problem for relaxed assumptions on the material coefficients. For instance we allow the contrast to change sign inside the medium. We also show how one can retrieve discreteness results for transmission eigenvalues in some particular situations. (10.1216/JIE-2013-25-3-341)
  DOI : 10.1216/JIE-2013-25-3-341
• Time reversal in viscoelastic media
  
  • Ammari Habib
  • Bretin Elie
  • Garnier Josselin
  • Wahab Abdul
  European Journal of Applied Mathematics, Cambridge University Press (CUP), 2013, 24, pp.565-600. In this paper, we consider the problem of reconstructing sources in a homogeneous viscoelastic medium from wavefield measurements using time-reversal algorithms. Our motivation is the recent advances on hybrid methods in biomedical imaging. We first present a modified time-reversal imaging algorithm based on a weighted Helmholtz decomposition and justify mathematically that it provides a better approximation than by simply time reversing the displacement field. Then, we investigate the source inverse problem in an elastic attenuating medium. We provide a regularized time-reversal imaging which corrects the attenuation effect at the first order.
• First and second order optimality conditions for optimal control problems of state constrained integral equations
  
  • Bonnans J. Frédéric
  • de La Vega Constanza
  • Dupuis Xavier
  Journal of Optimization Theory and Applications, Springer Verlag, 2013, 159 (1), pp.1-40. This paper deals with optimal control problems of integral equations, with initial-final and running state constraints. The order of a running state constraint is defined in the setting of integral dynamics, and we work here with constraints of arbitrary high orders. First and second-order necessary conditions of optimality are obtained, as well as second-order sufficient conditions. (10.1007/s10957-013-0299-3)
  DOI : 10.1007/s10957-013-0299-3
• Ecologie prédictive & changement planétaire
  
  • Austerlitz Frédéric
  • Blum Michael
  • Calba Sarah
  • Chave Jérôme
  • Choisy Marc
  • Coreau Audrey
  • Devictor Vincent
  • Doyen Luc
  • Dray Stéphane
  • Duputié Anne
  • Eveillard Damien
  • Faure Denis
  • Favier Charly
  • Gaggiotti Oscar
  • Galtier Nicolas
  • Garnier Éric
  • Gimenez Olivier
  • Guis Helene
  • Herbreteau Vincent
  • Huneman Philippe
  • Jabot Franck
  • Jarne Philippe
  • Joly Dominique
  • Julliard Romain
  • Kéfi Sonia
  • Kergoat Gael
  • Lacroix Gerard
  • Lagadeuc Yvan
  • Lavorel Sandra
  • Le Gaillard Jean-François
  • Le Gall Line
  • Loreau Michel
  • Maris Virginie
  • Morand Serge
  • Morin Xavier
  • Morlon Hélène
  • Mouquet Nicolas
  • Pinay Gilles
  • Pottier Julien
  • Pradel Roger
  • Ronce Ophélie
  • Schurr Frank
  • Simonet Pascal
  • Teplitsky Céline
  • Thuiller Wilfried
  • Tran Anne-Lise
  • Venner Samuel
  , 2013, hors s\'{e}rie, pp.9-44.
• Is the Distance Geometry Problem in NP?
  
  • Beeker Nathanael
  • Gaubert Stéphane
  • Glusa Christian
  • Liberti Leo
  , 2013, pp.85-93. (10.1007/978-1-4614-5128-0_5)
  DOI : 10.1007/978-1-4614-5128-0_5
• Méthodes de Monte-Carlo et processus stochastiques
  
  • Gobet Emmanuel
  , 2013, pp.258. La méthode de Monte-Carlo, qui tire son nom du fameux casino à Monaco, s’est développée de manière spectaculaire depuis 60 ans : elle figure parmi les 10 algorithmes ayant eu le plus d’influence sur le développement et la pratique de la science et de l’ingénierie au xxe siècle. En fait, il n’existe pas une méthode de Monte-Carlo mais des méthodes de Monte-Carlo. La 1re partie de l’ouvrage dresse un panorama de l’existant, puis détaille les outils de base pour la simulation de variables aléatoires, les résultats de convergence les plus courants et les techniques d’accélération des méthodes de Monte-Carlo. Puis, la 2e partie aborde la simulation des équations différentielles stochastiques (processus à évolution linéaire dérivant du mouvement brownien), dont les applications en biologie, chimie, économie, finance, géophysique, mécanique des fluides, neuroscience etc. sont importantes. L’objectif principal est le calcul d’espérance de leurs trajectoires. Cela donne, via les formules de Feynman-Kac, des solutions probabilistes aux équations aux dérivées partielles : ce lien remarquable permet de résoudre, par simulations Monte-Carlo, ces équations en toute dimension. Enfin, la 3e partie, la plus originale, traite des processus stochastiques ayant des évolutions non-linéaires (modélisant des interactions variées), comme les équations du contrôle stochastique, les diffusions branchantes, les équations stochastiques de McKean-Vlasov, avec des applications fondamentales en plein développement. Nous présentons notamment quelques idées importantes d’apprentissage statistique, dont le couplage aux méthodes de Monte-Carlo (via les régressions empiriques) conduit à des algorithmes des plus performants. Dans cet ouvrage, nous mettons en avant les grands principes de simulation efficace, avec une présentation exigeant le moins de préalables mathématiques. Le niveau prérequis à la lecture de ce cours est celui de Master 1, ou 2e année d’école d’ingénieurs. Cet ouvrage intéressera aussi des étudiants plus avancés ou des enseignants-chercheurs, souhaitant dégager l’essentiel des outils sophistiqués pour la simulation de processus stochastiques linéaires et non-linéaires.
• Minimal external representations of tropical polyhedra
  
  • Allamigeon Xavier
  • Katz R.D.
  Journal of Combinatorial Theory, Series A, Elsevier, 2013, 120 (4), pp.907-940. (10.1016/j.jcta.2013.01.011)
  DOI : 10.1016/j.jcta.2013.01.011
• Faddeev eigenfunctions for multipoint potentials
  
  • Grinevich Piotr
  • Novikov Roman
  Eurasian Journal of Mathematical and Computer Applications, Eurasian National University, Kazakhstan (Nur-Sultan), 2013, 1 (2), pp.76-91. We present explicit formulas for the Faddeev eigenfunctions and related generalized scattering data for multipoint potentials in two and three dimensions. For single point potentials in 3D such formulas were obtained in an old unpublished work of L.D. Faddeev. For single point potentials in 2D such formulas were given recently in [P.G. Grinevich, R.G. Novikov, Physics Letters A,376,(2012),1102-1106].
• Stochastic Simulation and Monte Carlo Methods. Mathematical Foundations of Stochastic Simulation.
  
  • Talay Denis
  • Graham Carl
  , 2013, 68, pp.268.
• Shape dependent controllability of a quantum transistor
  
  • Méhats Florian
  • Privat Yannick
  • Sigalotti Mario
  , 2013, pp.1253-1258.
• A decomposition technique for pursuit evasion games with many pursuers
  
  • Festa Adriano
  • Vinter Richard
  , 2013. Here we present a decomposition technique for a class of differential games. The technique consists in a decomposition of the target set which produces, for geometrical reasons, a decomposition in the dimensionality of the problem. Using some elements of Hamilton-Jacobi equations theory, we find a relation between the regularity of the solution and the possibility to decompose the problem. We use this technique to solve a pursuit evasion game with multiple agents.
• Tumor Growth Parameters Estimation and Source Localization From a Unique Time Point: Application to Low-grade Gliomas
  
  • Rekik Islem
  • Allassonnière Stéphanie
  • Clatz Olivier
  • Geremia Ezequiel
  • Stretton Erin
  • Delingette Hervé
  • Ayache Nicholas
  Computer Vision and Image Understanding, Elsevier, 2013, 117 (3), pp.238--249. Coupling time series of MR Images with reaction-di usion-based models has provided interesting ways to better understand the proliferative-invasive as- pect of glial cells in tumors. In this paper, we address a di erent formulation of the inverse problem: from a single time point image of a non-swollen brain tumor, estimate the tumor source location and the di usivity ratio between white and grey matter, while exploring the possibility to predict the further extent of the observed tumor at later time points in low-grade gliomas. The synthetic and clinical results show the stability of the located source and its varying distance from the tumor barycenter and how the estimated ratio controls the spikiness of the tumor. (10.1016/j.cviu.2012.11.001)
  DOI : 10.1016/j.cviu.2012.11.001