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Displaying 3741 – 3760 of 8747

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Margulis Lemma, entropy and free products

Filippo Cerocchi (2014)

Annales de l’institut Fourier

We prove a Margulis’ Lemma à la Besson-Courtois-Gallot, for manifolds whose fundamental group is a nontrivial free product A * B , without 2-torsion. Moreover, if A * B is torsion-free we give a lower bound for the homotopy systole in terms of upper bounds on the diameter and the volume-entropy. We also provide examples and counterexamples showing the optimality of our assumption. Finally we give two applications of this result: a finiteness theorem and a volume estimate for reducible manifolds.

Maslov indices on the metaplectic group M p ( n )

Maurice De Gosson (1990)

Annales de l'institut Fourier

We use the properties of M p ( n ) to construct functions μ : M p ( n ) Z 8 associated with the elements of the lagrangian grassmannian Λ (n) which generalize the Maslov index on Mp(n) defined by J. Leray in his “Lagrangian Analysis”. We deduce from these constructions the identity between M p ( n ) and a subset of S p ( n ) × Z 8 , equipped with appropriate algebraic and topological structures.

Mass endomorphism, surgery and perturbations

Bernd Ammann, Mattias Dahl, Andreas Hermann, Emmanuel Humbert (2014)

Annales de l’institut Fourier

We prove that the mass endomorphism associated to the Dirac operator on a Riemannian manifold is non-zero for generic Riemannian metrics. The proof involves a study of the mass endomorphism under surgery, its behavior near metrics with harmonic spinors, and analytic perturbation arguments.

Currently displaying 3741 – 3760 of 8747