Speaker
F. Orgogozo
(CNRS & École polytechnique)
Description
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.)
