Vendredi 17 Mai
Heure: 
00:59  13:30 
Lieu: 
Salle à fixer, Université de Villetaneuse 
Résumé: 
Are partial orderings intrinsic to computations? 
Description: 
Antonino Salibra Answering a question by Honsell and Plotkin, we show that there are two equations between lambda terms, the socalled subtractive equations, consistent with lambda calculus but not contemporaneously satisfied in any Scott continuous model. We also relate the subtractive equations to the open problem of the orderincompleteness of lambda calculus, by studying the connection between the notion of absolute unorderability in a specific point and a weaker notion of subtractivity, namely nsubtractivity, for partially ordered algebras. Finally we study the relation between nsubtractivity and relativized separation conditions in topological algebras, obtaining an incompleteness theorem for a general topological semantics of lambda calculus. 

