Fri Aug 26, 2016
60 Evans Hall, 4:10–6 PM
Martin Otto (Technische Universitaet Darmstadt)
Back & Forth Between Malleable Finite Models
This talk attempts to survey some model-theoretic techniques, model transformations and constructions - especially for logics of a modal/guarded flavour - that can replace classical compactness arguments, which are not available in restriction to finite models or other non-elementary classes of interest. Even where these algebraic-combinatorial and game-oriented techniques concur with the usually smoother infinitary methods of classical model theory they occasionally offer additional constructive or quantitative information. Some of the underlying combinatorial constructions to be discussed involve rather generic finite coverings for graphs and hypergraphs and are of independent interest. They can also be used towards alternative proofs of powerful extension properties for partial isomorphisms, which also have applications for the finite model theory of related logics.