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Spectral theory of translation surfaces : A short introduction

Luc Hillairet (2009/2010)

Séminaire de théorie spectrale et géométrie

We define translation surfaces and, on these, the Laplace operator that is associated with the Euclidean (singular) metric. This Laplace operator is not essentially self-adjoint and we recall how self-adjoint extensions are chosen. There are essentially two geometrical self-adjoint extensions and we show that they actually share the same spectrum

Stabilité simultanée de deux fonctions différentiables

Jean-Paul Dufour (1979)

Annales de l'institut Fourier

Nous caractérisons les couples de fonctions différentiables ( f , g ) , définies sur une variété compacte V de dimension 2 , qui sont simultanément stables en ce sens que, pour tout couple ( f ' , g ' ) assez voisin, il existe un difféomorphisme h de V et deux difféomorphismes λ et μ de R tels que h et λ échangent f et f ' alors que h et μ échangent g et g ' . L’outil essentiel est une technique de résolution des équations du type η ( x ) = X = ( x 2 + x 3 ) + ( 1 + x ) Y ( x 2 ) où les inconnues X et Y sont des fonctions de classe C .

Stochastic differential inclusions of Langevin type on Riemannian manifolds

Yuri E. Gliklikh, Andrei V. Obukhovskiĭ (2001)

Discussiones Mathematicae, Differential Inclusions, Control and Optimization

We introduce and investigate a set-valued analogue of classical Langevin equation on a Riemannian manifold that may arise as a description of some physical processes (e.g., the motion of the physical Brownian particle) on non-linear configuration space under discontinuous forces or forces with control. Several existence theorems are proved.

Stratifications of polynomial spaces

Lev Birbrair (1998)

Publicacions Matemàtiques

In the paper we construct some stratifications of the space of monic polynomials in real and complex cases. These stratifications depend on properties of roots of the polynomials on some given semialgebraic subset of R or C. We prove differential triviality of these stratifications. In the real case the proof is based on properties of the action of the group of interval exchange transformations on the set of all monic polynomials of some given degree. Finally we compare stratifications corresponding...

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 .

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