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Search Results: 1 - 10 of 117 matches for " Emeric Bouin "
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A Hamilton-Jacobi approach for front propagation in kinetic equations
Emeric Bouin
Mathematics , 2014,
Abstract: In this paper we use the theory of viscosity solutions for Hamilton-Jacobi equations to study propagation phenomena in kinetic equations. We perform the hydrodynamic limit of some kinetic models thanks to an adapted WKB ansatz. Our models describe particles moving according to a velocity-jump process, and proliferating thanks to a reaction term of monostable type. The scattering operator is supposed to satisfy a maximum principle. When the velocity space is bounded, we show, under suitable hypotheses, that the phase converges towards the viscosity solution of some constrained Hamilton-Jacobi equation which effective Hamiltonian is obtained solving a suitable eigenvalue problem in the velocity space. In the case of unbounded velocities, the non-solvability of the spectral problem can lead to different behavior. In particular, a front acceleration phenomena can occur. Nevertheless, we expect that when the spectral problem is solvable one can extend the convergence result.
Travelling waves for the cane toads equation with bounded traits
Emeric Bouin,Vincent Calvez
Mathematics , 2013, DOI: 10.1088/0951-7715/27/9/2233
Abstract: In this paper, we study propagation in a nonlocal reaction-diffusion-mutation model describing the invasion of cane toads in Australia. The population of toads is structured by a space variable and a phenotypical trait and the space-diffusivity depends on the trait. We use a Schauder topological degree argument for the construction of some travelling wave solutions of the model. The speed $c^*$ of the wave is obtained after solving a suitable spectral problem in the trait variable. An eigenvector arising from this eigenvalue problem gives the flavor of the profile at the edge of the front. The major difficulty is to obtain uniform $L^\infty$ bounds despite the combination of non local terms and an heterogeneous diffusivity.
A kinetic eikonal equation
Emeric Bouin,Vincent Calvez
Mathematics , 2012,
Abstract: We analyse the linear kinetic transport equation with a BGK relaxation operator. We study the large scale hyperbolic limit $(t,x)\to (t/\eps,x/\eps)$. We derive a new type of limiting Hamilton-Jacobi equation, which is analogous to the classical eikonal equation derived from the heat equation with small diffusivity. We prove well-posedness of the phase problem and convergence towards the viscosity solution of the Hamilton-Jacobi equation. This is a preliminary work before analysing the propagation of reaction fronts in kinetic equations.
A Hamilton-Jacobi approach for a model of population structured by space and trait
Emeric Bouin,Sepideh Mirrahimi
Mathematics , 2013,
Abstract: We study a non-local parabolic Lotka-Volterra type equation describing a population structured by a space variable x 2 Rd and a phenotypical trait 2 . Considering diffusion, mutations and space-local competition between the individuals, we analyze the asymptotic (long- time/long-range in the x variable) exponential behavior of the solutions. Using some kind of real phase WKB ansatz, we prove that the propagation of the population in space can be described by a Hamilton-Jacobi equation with obstacle which is independent of . The effective Hamiltonian is derived from an eigenvalue problem. The main difficulties are the lack of regularity estimates in the space variable, and the lack of comparison principle due to the non-local term.
Hyperbolic traveling waves driven by growth
Emeric Bouin,Vincent Calvez,Grégoire Nadin
Mathematics , 2011,
Abstract: We perform the analysis of a hyperbolic model which is the analog of the Fisher-KPP equation. This model accounts for particles that move at maximal speed $\epsilon^{-1}$ ($\epsilon>0$), and proliferate according to a reaction term of monostable type. We study the existence and stability of traveling fronts. We exhibit a transition depending on the parameter $\epsilon$: for small $\epsilon$ the behaviour is essentially the same as for the diffusive Fisher-KPP equation. However, for large $\epsilon$ the traveling front with minimal speed is discontinuous and travels at the maximal speed $\epsilon^{-1}$. The traveling fronts with minimal speed are linearly stable in weighted $L^2$ spaces. We also prove local nonlinear stability of the traveling front with minimal speed when $\epsilon$ is smaller than the transition parameter.
Super-linear spreading in local and non-local cane toads equations
Emeric Bouin,Christopher Henderson,Lenya Ryzhik
Mathematics , 2015,
Abstract: In this paper, we show super-linear propagation in a nonlocal reaction-diffusion-mutation equation modeling the invasion of cane toads in Australia that has attracted attention recently from the mathematical point of view. The population of toads is structured by a phenotypical trait that governs the spatial diffusion. In this paper, we are concerned with the case when the diffusivity can take unbounded values, and we prove that the population spreads as $t^{3/2}$. We also get the sharp rate of spreading in a related local model.
Propagation in a kinetic reaction-transport equation: travelling waves and accelerating fronts
Emeric Bouin,Vincent Calvez,Grégoire Nadin
Mathematics , 2013,
Abstract: In this paper, we study the existence and stability of travelling wave solutions of a kinetic reaction-transport equation. The model describes particles moving according to a velocity-jump process, and proliferating thanks to a reaction term of monostable type. The boundedness of the velocity set appears to be a necessary and sufficient condition for the existence of positive travelling waves. The minimal speed of propagation of waves is obtained from an explicit dispersion relation. We construct the waves using a technique of sub- and supersolutions and prove their \eb{weak} stability in a weighted $L^2$ space. In case of an unbounded velocity set, we prove a superlinear spreading. It appears that the rate of spreading depends on the decay at infinity of the velocity distribution. In the case of a Gaussian distribution, we prove that the front spreads as $t^{3/2}$.
Invasion fronts with variable motility: phenotype selection, spatial sorting and wave acceleration
Emeric Bouin,Vincent Calvez,Nicolas Meunier,Sepideh Mirrahimi,Benoit Perthame,Gael Raoul,Raphael Voituriez
Quantitative Biology , 2012,
Abstract: Invasion fronts in ecology are well studied but very few mathematical results concern the case with variable motility (possibly due to mutations). Based on an apparently simple reaction-diffusion equation, we explain the observed phenomena of front acceleration (when the motility is unbounded) as well as other quantitative results, such as the selection of the most motile individuals (when the motility is bounded). The key argument for the construction and analysis of traveling fronts is the derivation of the dispersion relation linking the speed of the wave and the spatial decay. When the motility is unbounded we show that the position of the front scales as $t^{3/2}$. When the mutation rate is low we show that the canonical equation for the dynamics of the fittest trait should be stated as a PDE in our context. It turns out to be a type of Burgers equation with source term.
An Autosomal STR Profile of Napoléon the First  [PDF]
Gérard Lucotte, Alexandra Bouin Wilkinson
Open Journal of Genetics (OJGen) , 2014, DOI: 10.4236/ojgen.2014.44027

Objective: We report the results of nuclear DNA analyses of Napoléon the First (Napoléon Bonaparte; 1769-1821). Design: His genomic DNA was extracted from dandruff adherent to his hair, coming from a lock of his hair dating from the year of 1811. Results: We obtained the complete STR (short tandem repeats) profile of Napoléon, based on fifteen autosomal loci. On this profile, ten loci (D8S1179, D21S11, D7S820, D3S1358, TH01, D16S539, D2S1338, vWa, D18S51 and FGA) are heterozygous; the most frequent alleles in Caucasians are present for only seven (allele 8 for TPOX and allele 11 for D5S818, allele 13 for D8S1179, allele 10 for D7S820, allele 9.3 for THO1, allele 12 for D16S539 and allele 24 for FGA) of the homozygous and heterozygous loci. Conclusions: So the discriminating power of this sort of genetic profile is elevated, permitting useful comparisons to other STR profiles in the future. Finally, an analysis of fifteen Y chromosomal STRs from the dandruff of this lock of hair confirms allele values of Napoléon already obtained or deduced for the corresponding loci in previous determinations.

Faire la ville suburbaine : le projet Sénart
Emeric Lambert
Articulo : Journal of Urban Research , 2009,
Abstract: En 1965 sont lancés en périphérie de Paris cinq projets de villes nouvelles dont Melun-Sénart est la cadette. La ville se voit refuser la création d’un centre-ville jusqu’en 1985. En 1986, Melun-Sénart devenu Sénart lance un concours d’idées pour se créer un centre. Les projets lauréats ne seront pas réalisés. L’aménageur de la ville propose un nouveau projet : le Carré Sénart. Ce carré de 1,4 km de c té est destiné à devenir un centre-ville. Il est subdivisé par une trame orthogonale dans laquelle s’insère notamment un nouveau centre commercial. Il accueille environ 10 millions de visiteurs par an et devient l’espace commun de la ville. Je propose de reconstruire la genèse du projet pour comprendre comment un projet de ville lancé par l’état a aujourd’hui un centre commercial pour centre-ville.
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