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Nombre de programmes trouvés : 631
Conférences

le (52m51s)

Burkhard Wilking - Manifolds with almost nonnegative curvature operator

We show that n-manifolds with a lower volume bound v and upper diameter bound D whose curvature operator is bounded below by $-\varepsilon(n,v,D)$ also admit metrics with nonnegative curvature operator. The proof relies on heat kernel estimates for the Ricci flow and shows that various smoothing properties of the Ricci flow remain valid if an upper curvature bound is replaced by a lower volume bound. nonnegative curvature operator.
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Conférences

le (52m41s)

F. Campana - Birational stability of the orbifold cotangent bundle

We show that a foliation on a projective complex manifold is algebraic with rationally connected (closure of) leaves exactly when its minimal slope with respect to some movable class is positive. This extends and strengthens former classical results by Y. Miyaoka and Bogomolov-McQuillan. Applications to foliations, hyperbolicity (a converse to a result of JP. Demailly) and moduli will be mentioned.This is a joint work with Mihai Paun, partly based on a former joint work with T.
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Conférences

le (51m50s)

Melanie Rupflin - Horizontal curves of metrics and applications to geometric flows

On closed surfaces there are three basic ways to evolve a metric, by conformal change, by pull-back with diffeomorphisms and by horizontal curves, moving orthogonally to the first two types of evolution. As we will discuss in this talk, horizontal curves are very well behaved even if the underlying conformal structures degenerate in moduli space as t to T. We can describe where the metrics will have essentially settled down to the limit by time t T as opposed to regions on which the metric still has to do an infinite amount of stretching. This quantified information is essential in ...
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Conférences

le (51m42s)

S. Donaldson - Boundary value problems for $G_2$ structures

In the lecture we consider the existence of G2 structures on 7-manifolds with boundary, with prescribed data on the boundary. In the first part we will review general background and theory, including Hitchin’s variational approach. We will then discuss in more detail reductions of the problem in the presence of symmetry and in ”adiabatic limits”, and connections with real and complex Monge-Ampère equations.
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