Valentin Shehtman

Talk on 3/6/15, 17h30: Bisimulation games and local finiteness

Bisimulation games are Kripke model analogues of Ehrenfeucht - Fraisse games (developed in classical model theory). In this talk we show how bisimulation games can simplify proofs of local finiteness of nonclassical propositional logics (or the corresponding varieties of algebras); a logic L is called locally finite if for any finite n there are finitely many formulas in n variables up to equivalence in L. Well-known results of this kind are the theorems by Segerberg - Maksimova and Kuznetsov - Komori on local finiteness of modal and intermediate logics of finite depth.  We propose various analogues of these theorems and discuss further lines of research.

Tutorial on 5/6/15, 10h00: Kripke models, bisimulations and bisimulation games

Kripke models are one of the main tools in modal and intuitionistic logic. Such a model can be presented as a labelled transition system with coloured states. Bisimulation is a natural relation associating Kripke models (or transition systems) with the same behaviour. Bisimulations can be constructed from bisimulation games; a winning strategy for the second player in this game gives a bisimulation. A recent application of bisimulation games is classification of formulas in modal logic; some examples will be given in this tutorial.

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