Vendredi 17 Mai

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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 so-called 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 order-incompleteness of lambda calculus, by studying the connection between the notion of absolute unorderability in a specific point and a weaker notion of subtractivity, namely n-subtractivity, for partially ordered algebras. Finally we study the relation between n-subtractivity and relativized separation conditions in topological algebras, obtaining an incompleteness theorem for a general topological semantics of lambda calculus.