2017


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Mercredi 30 Août
Heure: 11:00 - 12:30
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Coherence for skew near-semiring categories
Description: Tarmo Uustalu We consider skew near-semiring categories, a relaxation of
near-semiring categories where the unitors, associators, annihilator
and distributor are not required to be natural isomorphisms, they
are just natural transformations in a particular direction. We
prove a coherence theorem for such categories. The theorem states
that, in a free skew near-semiring category over a set of objects,
any two maps between an object and an object in normal form are
equal.

Our main motivating examples for skew near-semiring categories are from programming with effects. While (relative) monads and lax monoidal functors are the same as skew monoids in particular skew monoidal categories, (relative) MonadPlus and Alternative instances are skew near-semiring objects.

This is joint work with Mauro Jaskelioff, Exequiel Rivas and Niccolò Veltri.
Mardi 5 Septembre
Heure: 14:00 - 17:00
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: On the shape of random Pólya structures
Description: Michael Wallner
Mardi 19 Septembre
Heure: 14:00 - 17:00
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: TBA
Description: Valentin Bonzom
Vendredi 22 Septembre
Heure: 11:00 - 12:30
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Circular Proofs for Subtyping and Termination
Description: Rodolphe Lepigre In a recent (submitted) work with Christophe Raffalli, we designed a rich type
system for an extension of System F with subtyping. It includes primitive sums
and products, existential types, and (co-)inductive types. Using a combination
of (pointed) subtyping and circular proofs, we were able to express the system
with typing and subtyping rules that are syntax-directed (up to circularity).
During my talk, I will try to give you a flavour of the techniques we used. In
particular, I will show how choice operators can be used to get rid of typing
contexts, and to allow the commutation of quantifiers with other connectives.
I will then introduce the circular proof framework that is used for handling
inductive and co-inductive types in subtyping rules, and general recursion in
typing rules.
Vendredi 13 Octobre
Heure: 11:00 - 12:30
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Smooth models of Differential Linear Logic
Description: Marie Kerjean Differential Linear Logic was constructed following a study of discrete vectorial models of Linear Logic. We want to extend the semantics of Linear Logic in the natural domain of continuous objects and analysis. From the basic fact that Seely's formulas is the direct interpretation of the Kernel Theorem for distributions, we explain two developments :

On one hand we axiomatize a Smooth Differential Linear Logic with a graded syntax where to each solvable Linear partial differential equation one associate an exponential. We construct a model of nuclear Fréchet/ Df spaces for this syntax.

On the other hand, we argue that the interpretation of the $parr$ as Schwartz's epsilon product should be the cornestone of the construction of a smooth classical model of DiLL. From a first-model of $k$-reflexive spaces, and based on pioneering works by Kriegl, Michor and Meise, we construct a variety of (at least two) new models of DiLL. This part is joint work with Y. Dabrowski.
Vendredi 20 Octobre
Heure: 11:00 - 12:30
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Inlining après l'élimination de fermeture pour OCaml
Description: Pierre Chambart Usuellement, dans les langages de haut niveau, l'inlining est fait sur
un langage intermédiaire proche d'un lambda calcul, où celà revient
pour les cas simple à de la beta-réduction. Pour diverses raisons,
dans OCaml, nous avons décidé d'introduire un autre langage
intermédiaire où les fermetures sont explicite (flambda) sur lequel
les optimisations haut niveau sont effectuées. Nous discuterons des
avantages et complexités qui viennent avec ce choix.
Mardi 24 Octobre
Heure: 14:00 - 17:00
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: Bijections for Weyl Chamber walks ending on an axis, and arc diagrams
Description: Mathias Lepoutre
Heure: 15:30 - 18:30
Lieu: Salle B107, bâtiment B, Université de Villetaneuse
Résumé: False Beliefs in mathematics
Description: thé combinatoire