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Nombre de programmes trouvés : 2756
Conférences

le (1h28m18s)

Attention, zone contaminée Conférence dans le cadre de l'Université Populaire du Havre avec Frédérick Lemarchand et Cathy Blisson

Tchernobyl en 1986, Fukushima en 2011 : avons-nous tiré tous les enseignements de ces catastrophes nucléaires et de leurs conséquences humaines ? Comment aujourd’hui traiter des risques technologiques majeurs ? Pour le sociologue Frédérick Lemarchand, appréhender les menaces produites par l’homme sous le seul angle du "risque calculable" est un facteur d’aggravation des situations de crise, voire un moteur. Seule une approche complexe et pluridisciplinaire, avec l’apport des sciences sociales et humaines et l’aval de la société civile, peut être à la hauteur de tels enjeux. Cette réflexion se place sous ...
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Cours magistraux

le (1h28m21s)

Sylvain Maillot - An introduction to open 3-manifolds (Part 2)

W. Thurston's geometrization program has lead to manyoutstanding results in 3-manifold theory. Thanks to worksof G. Perelman, J. Kahn and V. Markovic, D. Wise, and I. Agol among others, compact 3-manifolds can now beconsidered to be reasonably well-understood.By contrast, noncompact 3-manifolds remainmuch more mysterious. There is a series of examples,beginning with work of L. Antoine and J. H. C. Whitehead,which show that open 3-manifolds can exhibit wildbehavior at infinity. No comprehensive structure theoryanalogous to geometrization à la Thurston is currently availablefor these objectsIn these lectures, we will focus on two aspects of the subject:(1) constructing interesting examples, and(2) finding sufficientconditions ...
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Cours magistraux

le (1h28m28s)

J. Aramayona - MCG and infinite MCG (Part 3)

The first part of the course will be devoted to some of the classical results about mapping class groups of finite-type surfaces. Topics may include: generation by twists, Nielsen-Thurston classification, abelianization, isomorphic rigidity, geometry of combinatorial models. In the second part we will explore some aspects of "big" mapping class groups, highlighting the analogies and differences with their finite-type counterparts, notably around isomorphic rigidity, abelianization, and geometry of combinatorial models.
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Cours magistraux

le (1h28m36s)

Robert Young - Quantitative geometry and filling problems (Part 5)

Plateau's problem asks whether there exists a minimal surface with a given boundary in Euclidean space. In this course, we will study related problems in broader classes of spaces and ask what the asymptotics of filling problems tell us about the geometry of surfaces in groups and spaces. What do minimal and nearly minimal surfaces look like in different spaces, and how is the geometry of surfaces related to the geometry of the ambient space? Our main examples will arise from geometric group theory, including nilpotent groups and symmetric spaces.
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Cours magistraux

le (1h28m48s)

E. Peyre - Slopes and distribution of points (part4)

The distribution of rational points of bounded height on algebraic varieties is far from uniform. Indeed the points tend to accumulate on thin subsets which are images of non-trivial finite morphisms. The problem is to find a way to characterise these thin subsets. The slopes introduced by Jean-Benoît Bost are a useful tool for this problem. These lectures will present several cases in which this approach is fruitful. We shall also describe the notion of locally accumulating subvarieties which arise when one considers rational points of ...
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Conférences

le (1h28m54s)

Dernières nouvelles du rayonnement fossile (IAP)

Conférence de l'Institut d'Astrophysique de Paris présentée par Karim Benabed, astrophysicien à l'IAP, le 4 novembre 2014 à l'IAP.Depuis l'annonce des premiers résultats cosmologiques basés sur le relevé du fond de ciel micro-onde réalisé par la mission satellite européenne Planck début 2013, l'actualité de ce rayonnement extrêmement froid (3 Kelvin), signature du big bang, émis il y a près de 14 milliard d'années, est brûlante ! En effet, une expérience américaine, BICEP, basé au Pole Sud a depuis annoncé une possible détection, dans leur propre relevé ...
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Cours magistraux

le (1h29m6s)

Robert Young - Quantitative geometry and filling problems (Part 3)

Plateau's problem asks whether there exists a minimal surface with a given boundary in Euclidean space. In this course, we will study related problems in broader classes of spaces and ask what the asymptotics of filling problems tell us about the geometry of surfaces in groups and spaces. What do minimal and nearly minimal surfaces look like in different spaces, and how is the geometry of surfaces related to the geometry of the ambient space? Our main examples will arise from geometric group theory, including nilpotent groups and symmetric spaces.
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Cours magistraux

le (1h29m10s)

Thomas Richard - Lower bounds on Ricci curvature, with a glimpse on limit spaces (Part 1)

The goal of these lectures is to introduce some fundamental tools in the study of manifolds with a lower bound on Ricci curvature. We will first state and prove the laplacian comparison theorem for manifolds with a lower bound on the Ricci curvature, and derive some important consequences : Bishop-Gromov inequality, Myers theorem, Cheeger-Gromoll splitting theorem. Then we will define the Gromov-Hausdorff distance between metric spaces which will allow us to consider limits of sequences of Riemannian manifolds, along the way we will prove ...
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