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Documents  Ramond, Thierry | enregistrements trouvés : 7

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Research talks;Partial Differential Equations;Mathematical Physics

We consider short-range perturbations of elliptic operators on $R^d$ with constant coefficients, and study the asymptotic properties of the scattering matrix as the energy tends to infinity. We give the leading terms of the symbol of the scattering matrix. The proof employs semiclassical analysis combined with a generalization of the Isozaki-Kitada theory on time-independent modifiers. We also consider scattering matrices for 2 and 3 dimensional Dirac operators. (joint work with Alexander Pushnitski (King’s College London) We consider short-range perturbations of elliptic operators on $R^d$ with constant coefficients, and study the asymptotic properties of the scattering matrix as the energy tends to infinity. We give the leading terms of the symbol of the scattering matrix. The proof employs semiclassical analysis combined with a generalization of the Isozaki-Kitada theory on time-independent modifiers. We also consider scattering matrices for 2 and 3 dimensional ...

35P25 ; 35J10 ; 81U20

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Outreach;Mathematics Education and Popularization of Mathematics

Sylvia Serfaty is a Professor at the Laboratoire Jacques-Louis Lions, Université Pierre et Marie Curie Paris 6. Sylvia Serfaty was a Global Distinguished Professor of Mathematics in the Courant Institute of Mathematical Sciences. She has been awarded a Sloan Foundation Research Fellowship and a NSF CAREER award (2003), the 2004 European Mathematical Society Prize, 2007 EURYI (European Young Investigator) award, and has been invited speaker at the International Congress of Mathematicians (2006), Plenary speaker at the European Congress of Mathematics (2012) and has recently received the IAMP Henri Poincar´e prize in 2012. Her research is focused on the study of Nonlinear Partial Differential Equations, calculus of variations and mathematical physics, in particular the Ginzburg-Landau superconductivity model. Sylvia Serfaty was the first to make a systematic and impressive asymptotic analysis for the case of large parameters in theory of the Ginzburg-Landau equation. She established precisely, with Etienne Sandier, the values of the first critical fields for nucleation of vortices in superconductors, as well as the leading and next to leading order effective energies that govern the location of these vortices and their arrangement in Abrikosov lattices In micromagnetics, her work with F. Alouges and T. Rivière breaks new ground on singularly perturbed variational problems and provides the first explanation for the internal structure of cross-tie walls.
http://www.ams.org/journals/notices/200409/people.pdf
Personal page : http://www.ann.jussieu.fr/~serfaty/
Sylvia Serfaty is a Professor at the Laboratoire Jacques-Louis Lions, Université Pierre et Marie Curie Paris 6. Sylvia Serfaty was a Global Distinguished Professor of Mathematics in the Courant Institute of Mathematical Sciences. She has been awarded a Sloan Foundation Research Fellowship and a NSF CAREER award (2003), the 2004 European Mathematical Society Prize, 2007 EURYI (European Young Investigator) award, and has been invited speaker at ...

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Research talks;Mathematical Physics

In this talk, I will consider a quantum particle interacting with a target. The target is supposed to be localized and the dynamics of the particle is supposed to be generated by a Lindbladian acting on the space of trace class operators. I will discuss scattering theory for such models associated to a Lindblad operator. First, I will consider situations where the incident particle is necessarily scattered off the target, next situations where the particle may be captured by the target. An important ingredient of the analysis consists in studying scattering theory for dissipative operators on Hilbert spaces.
This is joint work with Marco Falconi, Juerg Froehlich and Baptiste Schubnel.
In this talk, I will consider a quantum particle interacting with a target. The target is supposed to be localized and the dynamics of the particle is supposed to be generated by a Lindbladian acting on the space of trace class operators. I will discuss scattering theory for such models associated to a Lindblad operator. First, I will consider situations where the incident particle is necessarily scattered off the target, next situations where ...

47A40 ; 47N50 ; 82C10

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Research talks;Mathematical Physics

We consider a general network of harmonic oscillators driven out of thermal equilibrium by coupling to several heat reservoirs at different temperatures. The action of the reservoirs is implemented by Langevin forces. Assuming the existence and uniqueness of the steady state of the resulting process, we construct a canonical entropy production functional $S(t)$ which satisfies the Gallavotti-Cohen fluctuation theorem. More precisely, we prove that cumulant generating function of $S(t)$ has a large-time limit $e(a)$ which is finite on a closed interval centered at $a=1/2$, infinite on its complement and satisfies the Gallavotti-Cohen symmetry $e(1-a)=e(a)$ for all $a$. It follows from well known results that $S(t)$ satisfies a global large deviation principle with a rate function $I(s)$ obeying the Gallavotti-Cohen fluctuation relation $I(-s)-I(s)=s$ for all $s$. We also consider perturbations of $S(t)$ by quadratic boundary terms and prove that they satisfy extended fluctuation relations, i.e., a global large deviation principle with a rate function that typically differs from $I(s)$ outside a finite interval. This applies to various physically relevant functionals and, in particular, to the heat dissipation rate of the network. Our approach relies on the properties of the maximal solution of a one-parameter family of algebraic matrix Ricatti equations. It turns out that the limiting cumulant generating functions of $S(t)$ and its perturbations can be computed in terms of spectral data of a Hamiltonian matrix depending on the harmonic potential of the network and the parameters of the Langevin reservoirs. This makes our approach well adapted to both analytical and numerical investigations. This is joint work with Vojkan Jaksic and Armen Shirikyan. We consider a general network of harmonic oscillators driven out of thermal equilibrium by coupling to several heat reservoirs at different temperatures. The action of the reservoirs is implemented by Langevin forces. Assuming the existence and uniqueness of the steady state of the resulting process, we construct a canonical entropy production functional $S(t)$ which satisfies the Gallavotti-Cohen fluctuation theorem. More precisely, we prove ...

82C10 ; 82C70

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Research talks;Partial Differential Equations;Mathematical Physics

Ginzburg-Landau type equations are models for superconductivity, superfluidity, Bose-Einstein condensation, etc. A crucial feature is the presence of quantized vortices, which are topological zeroes of the complex-valued solutions. We will present a new result on the derivation of a mean-field limit equation for the dynamics of many vortices starting from the parabolic Ginzburg-Landau equation or the Gross-Pitaevskii (=Schrodinger Ginzburg-Landau) equation. Ginzburg-Landau type equations are models for superconductivity, superfluidity, Bose-Einstein condensation, etc. A crucial feature is the presence of quantized vortices, which are topological zeroes of the complex-valued solutions. We will present a new result on the derivation of a mean-field limit equation for the dynamics of many vortices starting from the parabolic Ginzburg-Landau equation or the Gross-Pitaevskii (=Schrodinger Ginzb...

35Q55 ; 35Q56 ; 82D55

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Research talks;Exposés de recherche;Partial Differential Equations;Mathematical Physics

We study the survival probability associated with a semiclassical matrix Schrödinger operator that models the predissociation of a general molecule in the Born-Oppenheimer approximation. We show that it is given by its usual time-dependent exponential contribution, up to a reminder term that is small in the semiclassical parameter and for which we find the main contribution. The result applies in any dimension, and in presence of a number of resonances that may tend to infinity as the semiclassical parameter tends to 0.
This is a joint work with Ph. Briet.
We study the survival probability associated with a semiclassical matrix Schrödinger operator that models the predissociation of a general molecule in the Born-Oppenheimer approximation. We show that it is given by its usual time-dependent exponential contribution, up to a reminder term that is small in the semiclassical parameter and for which we find the main contribution. The result applies in any dimension, and in presence of a number of ...

35B34 ; 35P15 ; 35J10 ; 47A75 ; 81Q15

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- vii; 314 p.
ISBN 978-2-85629-894-7

Astérisque , 0405

Localisation : Périodique 1er étage

résonance # asymptotique semiclassique # analyse microlocale # trajectoire homocline et hétérocline # opérateur de Schrödinger

35B34 ; 35P20 ; 37C29 ; 37C25 ; 35C20 ; 81Q20 ; 35S10 ; 35J10

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