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Résidus des connexions à singularités et classes caractéristiques

Daniel Lehmann (1981)

Annales de l'institut Fourier

Un “théorème des résidus” est donné, qui exprime les classes caractéristiques réelles de dimension 2 k d’un fibré principal C à l’aide d’une connexion définie seulement au-dessus d’un voisinage du ( 2 k - 1 ) -squelette d’une triangulation de la base. Ce théorème coiffe simultanément la théorie de Chern-Weil, la théorie de l’obstruction modulo torsion, ainsi que des formules du type Riemann-Hurwitz pour les revêtements ramifiés.

Resolutions of moduli spaces and homological stability

Oscar Randal-Williams (2016)

Journal of the European Mathematical Society

We describe partial semi-simplicial resolutions of moduli spaces of surfaces with tangential structure. This allows us to prove a homological stability theorem for these moduli spaces, which often improves the known stability ranges and gives explicit stability ranges in many new cases. In each of these cases the stable homology can be identified using the methods of Galatius, Madsen, Tillmann and Weiss.

The computation of Stiefel-Whitney classes

Pierre Guillot (2010)

Annales de l’institut Fourier

The cohomology ring of a finite group, with coefficients in a finite field, can be computed by a machine, as Carlson has showed. Here “compute” means to find a presentation in terms of generators and relations, and involves only the underlying (graded) ring. We propose a method to determine some of the extra structure: namely, Stiefel-Whitney classes and Steenrod operations. The calculations are explicitly carried out for about one hundred groups (the results can be consulted on the Internet).Next,...

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