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Nombre de programmes trouvés : 3064
Cours magistraux

le (2h4m52s)

Jérémie Szeftel The resolution of the bounded L2 curvature conjecture in General Relativity (Part 2)

In order to control locally a space-­‐time which satisfies the Einstein equations, what are the minimal assumptions one should make on its curvature tensor? The bounded L2 curvature conjecture roughly asserts that one should only need L2 bounds of the curvature tensor on a given space-­‐like hypersurface. This conjecture has its roots in the remarkable developments of the last twenty years centered around the issue of optimal well-­‐posedness for nonlinear wave equations. In this context, a corresponding conjecture for nonlinear wave equations cannot hold, unless the nonlinearity has a very special nonlinear structure. I will present the proof of this ...
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Cours magistraux

le (2h4m58s)

Rod Gover - An introduction to conformal geometry and tractor calculus (Part 2)

After recalling some features (and the value of) the invariant ``Ricci calculus'' of pseudo-­‐Riemannian geometry, we look at conformal rescaling from an elementary perspective. The idea of conformal covariance is visited and some covariant/invariant equations from physics are recovered in this framework. Motivated by the need to develop a more effective approach to such problems we are led into the idea of conformal geometry and a conformally invariant calculus; this``tractor calculus'' is then developed explicitly. We will discuss how to calculate using this, and touch on applications to the construction of conformal invariants and conformally invariant differential operators. The second ...
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Cours magistraux

le (2h5m33s)

Christian Gérard - Introduction to field theory on curved spacetimes (Part 3)

The aim of these lectures is to give an introduction to quantum field theory on curved spacetimes, from the point of view of partial differential equations and microlocal analysis. I will concentrate on free fields and quasi-free states, and say very little on interacting fields or perturbative renormalization. I will start by describing the necessary algebraic background, namely CCR and CAR algebras, and the notion of quasi-free states, with their basic properties and characterizations. I will then introduce the notion of globally hyperbolic spacetimes, and its importance for classical field theory (advanced and retarded fundamental solutions, unique solvability of the ...
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Cours magistraux

le (2h7m51s)

Andras Vasy - Microlocal analysis and wave propagation (Part 2)

In these lectures I will explain the basics of microlocal analysis, emphasizing non elliptic problems, such as wave propagation, both on manifolds without boundary, and on manifolds with boundary. In the latter case there is no `standard' algebra of differential, or pseudodifferential, operators; I will discuss two important frameworks: Melrose's totally characteristic, or b, operators and scattering operators. Apart from the algebraic and mapping properties, I will discuss microlocal ellipticity, real principal type propagation, radial points and generalizations, as well as normally hyperbolic trapping. The applications discussed will include Fredholm frameworks (which are thus global even for non elliptic problems!) ...
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Cours magistraux

le (2h8m16s)

Andras Vasy - Microlocal analysis and wave propagation (Part 4)

In these lectures I will explain the basics of microlocal analysis, emphasizing non elliptic problems, such as wave propagation, both on manifolds without boundary, and on manifolds with boundary. In the latter case there is no `standard' algebra of differential, or pseudodifferential, operators; I will discuss two important frameworks: Melrose's totally characteristic, or b, operators and scattering operators. Apart from the algebraic and mapping properties, I will discuss microlocal ellipticity, real principal type propagation, radial points and generalizations, as well as normally hyperbolic trapping. The applications discussed will include Fredholm frameworks (which are thus global even for non elliptic problems!) ...
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Label UNT Conférences

le (2h8m34s)

Internet et sécurité des données

Les mots de passe sont partout en informatique. Ils sont la principale défense offerte à tous les utilisateurs d'Internet (de l'expert au néophyte) pour protéger leurs informations (vos mails ou contacts) ou leurs réputations des forces malveillantes. Nos mots de passe sont donc l'objet de la convoitise de nombreuses personnes (crime organisé ou organisme d'état) et il existe de nombreuses stratégies pour un attaquant pour vous dérober votre mot de passe: cassage de mot de passe, hameçonnage plus ou moins avancé. Durant cette présentation, nous ...
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Cours magistraux

le (2h9m59s)

Jean-Pierre Demailly - Kobayashi pseudo-metrics, entire curves and hyperbolicity of algebraic varieties (Part 4)

We will first introduce the basic concepts pertaining to Kobayashi pseudo-distances and hyperbolic complex spaces, including Brody’s theorem and the Ahlfors-Schwarz lemma. One of the main goals of the theory is to understand conditions under which a given algebraic variety is Kobayashi hyperbolic. This leads to the introduction of jet spaces and jet metrics, and provides a strong link between the existence of entire curves and the existence of global algebraic differential equations.  
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Conférences

le (2h12m0s)

A-t-on enterré l'espace public ? Partie 1

Journées d’études organisées par Publislam et le réseau Pratiques Politiques locales (Iris), Ecole des Hautes Etudes en Sciences Sociales (EHESS), Paris. Le concept d’espace public – concept générique, analytique ou normatif – a occupé, pendant plusieurs décennies, une place centrale dans la pensée du politique. Mais aujourd’hui son usage connaît à la fois des décentrements et une certaine relégation. D’une part, sa fécondité heuristique semble s’étioler : dans les sociétés occidentales contemporaines des notions voisines, mais alternatives, prétendent s’y substituer, conduisant à une sorte de disqualification qui mérite d’être analysée. D’autre part, il est enrôlé pour analyser des situations ...
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