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Séminaire de Théorie Algorithmique des Nombres

Point counting on curves over finite fields

Rob de Jeu

( Vrije Universiteit Amsterdam )

Salle 2

le 17 décembre 2024 à 11:00

We discuss a rather general algorithm for point counting on a (nice) curve over a finite field of characteristic p, assuming a lift to the valuation ring in a finite extension of Q_p has been given. Our method for computing the action of Frobenius is based on computing cup products in cohomology, not on explicitly rewriting 1-forms using exact 1-forms. These cup products can be computed locally, and the same holds for the local expansions of a lift of Frobenius that is determined uniquely by some global equations. This is joint work with Amnon Besser, Pengju Guan, and Muxi Li.