Vendredi 14 Mars
Heure: 
10:00  12:00 
Lieu: 
Salle B107, bâtiment B, Université de Villetaneuse 
Résumé: 
On type isomorphisms in simultaneous presence of sums and functions 
Description: 
Danko Ilik We consider the problem of characterizing isomorphisms of types, or, equivalently, constructive cardinality of sets, in the simultaneous presence of disjoint unions, Cartesian products, and exponentials. Mostly relying on results about polynomials with exponentiation that have not been used in our context, we derive: that the usual finite axiomatization known as HighSchool Identities (HSI) is complete for a significant subclass of types; that it is decidable for that subclass when two types are isomorphic; that, for the whole of the set of types, a recursive extension of the axioms of HSI exists that is complete; and that, for the whole of the set of types, the question as to whether two types are isomorphic is decidable when base types are to be interpreted as finite sets. We also point out certain related open problems. 

