25 Mai - 31 Mai

Retour à la vue des calendrier
Mardi 26 Mai
Heure: 14:00 - 17:00
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Efficient Algebraic Diagonals and Walks
Description: Louis Dumont The diagonal of a multivariate power series F is the univariate power series Diag F generated by the diagonal terms of F. Diagonals form an important class of power series; they occur frequently in number theory, theoretical physics and enumerative combinatorics. Westudy algorithmic questions related to diagonals in the case where F is the Taylor expansion of a bivariate rational function. It is classical that in this case Diag F is an algebraic function. We propose an algorithm that computes an annihilating polynomial forDiag F. Generically, it is its minimal polynomial and is obtained in time quasi-linear in its size. We show that this minimal polynomial has an exponential size with respect to the degree of the input rational function. Throughout the talk, we use a common problemof counting certain lattice walks to illustrate the capacities and limits of our tools.
Mercredi 27 Mai
Heure: 14:00 - 16:00
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Logics via algebras and substitutions
Description: Antonino Salibra In this talk we present a translation of formulas and models of classical and non-classical logics
into factor algebras. The correspondence:
Propositional variables --- operator of decompositions
Logical operations --- substitutions
Formulas --- algebraic terms
Models --- factor algebras,
provides a uniform calculus of provability for all the logics which admit the translation.
Many examples will be discussed:
classical logic, intuitionistic logic, linear logic, many-valued logics.