Deligne's geometrical approach to the product formula for l-adic epsilon factors

Jun 15, 2018, 11:45 AM
Centre de Conférences Marilyn et James Simons (Le Bois-Marie)

Centre de Conférences Marilyn et James Simons

Le Bois-Marie

35, route de Chartres 91440 Bures-sur-Yvette


F. Orgogozo (CNRS & École polytechnique)


Around 1985, Gérard Laumon gave a proof of the local factorization of the determinant of the Frobenius map acting on the cohomology of a curve. Shortly before Laumon's work, however, Deligne had developed a different approach to the problem, which is not well known today. In this talk, I would like to introduce Deligne's method to a wider audience, in the hope that its full potential has yet to be exploited. Its starting point is Deligne's symmetric Künneth formula and the acyclicity properties of the Abel-Jacobi morphism, which led to the first proof of the result in the tame case. (Understanding Deligne's method is one part of an ongoing project with Joël Riou.)

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