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Nombre de programmes trouvés : 888
Conférences

le (53m0s)

C.Fougeron - Diffusion rate for windtree models

Recent results on windtree models with polygonal obstacles have linked their diffusion rate with Lyapunov exponents in stata of quadratic differentials.  The proves of these theorems follow from the numerous symmetries of the studied examples.  In this talk I will present a general method for this purpose in a more general setting using the lattest advances on the structure of the orbit closure oftranslation surfaces and their Hodge bundle.
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Conférences

le (56m7s)

V. Gadre - Effective convergence of ergodic averages and cusp excursions of geodesics

Effective convergence of ergodic averages and cusp excursions of geodesics on moduli spacesWe survey some applications of effective convergence of ergodic averages to the analysis of cusp ex-cursions of typical geodesics on moduli spaces. This will cover Teichmuller geodesics, Weil-Peterssongeodesics and geodesics typical for harmonic measures arising from random walks on mapping class groups.
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Séminaires

le (56m49s)

Stéphane Jaffard - Quelle est la régularité de la fonction de Brjuno ?

Introduite par J.-C. Yoccoz, la fonction de Brjuno fournit une information importante sur les problèmes de petits diviseurs analytiques. Elle semble ne posséder aucune régularite en un sens raisonnable: elle n'est nulle part localement bornée, et on ne peut donc même pas essayer de tracer son graphe. Cette question va cependant nous permettre de revisiter et de relier plusieurs domaines apparemment éloignés. La recherche d'une notion de régularité ponctuelle adaptée à la fonction de Brjuno nous conduira aux travaux des années 1960 ...
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Conférences

le (35m48s)

Z. Badreddine - Optimal transportation problem and MCP property on sub-Riemannian structures

This presentation is devoted to the study of mass transportation on sub-Riemannian geometry. In order to obtain existence and uniqueness of optimal transport maps, the first relevant method to consider is the one used by Figalli and Rifford which is based on the local semiconcavity of the sub-Riemannian distance outside the diagonal. Recently, Cavalletti and Huesmann developed a new method to solve the Monge problem using a measure contraction property. That is why we attempt to prove the MCP property on sub-Riemannian structures as a consequence ...
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Conférences

le (24m48s)

G. Molino - The Horizontal Einstein Property for H-Type sub-Riemannian Manifolds

We generalize the notion of H-type sub-Riemannian manifolds introduced by Baudoin and Kim, and then introduce a notion of parallel Clifford structure related to a recent work of Moroianu and Semmelmann. On those structures, we prove an Einstein property for the horizontal distribution using ideas from Ishihara’s work on hyper-Kahler and bquaternionic Kahler manifolds. This is a joint work with F. Baudoin, E. Grong, and L. Rizzi.
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Conférences

le (44m42s)

D. Prandri - Weyl law for singular Riemannian manifolds

In this talk we present recent results on the asymptotic growth of eigenvalues of the Laplace-Beltrami operator on singular Riemannian manifolds, where all geometrical invariants appearing in classical spectral asymptotics are unbounded, and the total volume can be infinite. Under suitable assumptions, we prove that the leading term of the Weyl’s asymptotics contains information on the singularity, i.e. its Minkowski dimension and its regularized measure. We apply our results to a suitable class of almost-Riemannian structures. A key tool in the proof is a ...
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Conférences

le (19m5s)

F. Boarotto - Normal forms around regular abnormal curves in rank-two distributions (Part 1)

Let (M, ∆) be a rank-two sub-Riemannian structure on a smooth manifold M, and let x, y be any two points on M. In this talk I will present some recent results concerning the description of the set Ω(y), of all the horizontal curves joining x and y, in the vicinity of a rank-two-nice singular curve γ. This is made possible by the existence of a normal form for the endpoint map F locally around γ, and in turn this result permits to discuss some rather surprising isolation ...
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Conférences

le (16m44s)

F. Boarotto - Normal forms around regular abnormal curves in rank-two distributions (Part 2)

Let (M, ∆) be a rank-two sub-Riemannian structure on a smooth manifold M, and let x, y be any two points on M. In this talk I will present some recent results concerning the description of the set Ω(y), of all the horizontal curves joining x and y, in the vicinity of a rank-two-nice singular curve γ. This is made possible by the existence of a normal form for the endpoint map F locally around γ, and in turn this result permits to discuss some rather surprising isolation ...
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Conférences

le (41m53s)

V. Franceschi - Sub-riemannian soap bubbles

The aim of this seminar is to present some results about minimal bubble clusters in some sub-Riemannian spaces. This amounts to finding the best configuration of m ∈ N regions in a manifold enclosing given volumes, in order to minimize their total perimeter. In a n-dimensional sub-Riemannian manifold, the perimeter is a non-isotropic (n − 1)-dimensional measure that is defined according to the geometry. After an introduction to the subject, we will present some results concerning the cases m = 1 (isoperimetric problem) and m = ...
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