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Strong density for higher order Sobolev spaces into compact manifolds

Pierre Bousquet, Augusto C. Ponce, Jean Van Schaftingen (2015)

Journal of the European Mathematical Society

Given a compact manifold N n , an integer k * and an exponent 1 p < , we prove that the class C ( Q ¯ m ; N n ) of smooth maps on the cube with values into N n is dense with respect to the strong topology in the Sobolev space W k , p ( Q m ; N n ) when the homotopy group π k p ( N n ) of order k p is trivial. We also prove density of maps that are smooth except for a set of dimension m - k p - 1 , without any restriction on the homotopy group of N n .

Sur le théorème des fonctions composées différentiables

Jean-Jacques Risler (1982)

Annales de l'institut Fourier

Soit f : X Y un morphisme propre relativement algébrique entre espaces semi-analytiques. On montre que si 𝒞 ( Y ) désigne l’anneau des fonctions de classe 𝒞 sur Y , l’image par f de 𝒞 ( Y ) est fermée dans 𝒞 ( X ) muni de sa topologie naturelle d’espace de Frechet ; ceci généralise un résultat précédent de J.-C. Tougeron (lui-même généralisant un résultat de Glaeser) qui traite du cas semi-algébrique. La méthode est tout à fait analogue et utilise des propriétés algébriques de l’anneau des fonctions Nash-analytiques introduit...

The Lie group of real analytic diffeomorphisms is not real analytic

Rafael Dahmen, Alexander Schmeding (2015)

Studia Mathematica

We construct an infinite-dimensional real analytic manifold structure on the space of real analytic mappings from a compact manifold to a locally convex manifold. Here a map is defined to be real analytic if it extends to a holomorphic map on some neighbourhood of the complexification of its domain. As is well known, the construction turns the group of real analytic diffeomorphisms into a smooth locally convex Lie group. We prove that this group is regular in the sense of Milnor. ...

Variational calculus on Lie algebroids

Eduardo Martínez (2008)

ESAIM: Control, Optimisation and Calculus of Variations

It is shown that the Lagrange's equations for a Lagrangian system on a Lie algebroid are obtained as the equations for the critical points of the action functional defined on a Banach manifold of curves. The theory of Lagrangian reduction and the relation with the method of Lagrange multipliers are also studied.

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