The project is on the borderline between model theory (mathematical logic) and permutation group theory (algebra), though ideas from other fields such as set theory and combinatorics are involved. The goal is to investigate the following question for a range of first order structures: if one knows the automorphism group Aut(M) of a countable first order structure M, how much is known about M?
The question only makes sense in highly symmetric contexts, such as for omega-categorical structures. Work on reconstruction so far has mainly centred on the small index property, which enables one to recover the topology on Aut(M) from the pure group, and hence to recover M up to bi-interpretability. The proposal is partly to obtain reconstruction results for new classes of structures, by developing new methods for cases where current techniques fail; and partly to prove positive results on a new kind of reconstruction, namely interpretability of a structure in its automorphism group.
The main candidates for investigation are a class of combinatorial constructions due to Hrushovski, which are crucial in model-theoretic simplicity theory, and the class of smoothly approximable structures. The latter have a natural algebraic characterization in terms of covers of classical geometries. The intended methods stem from an approach to reconstruction developed by M. Rubin, which has been neglected in the published literature so far. The proposed approach will involve the notion of generic automorphism, which is highly relevant t o reconstruction and has also independent interest. Applications to reconstruction questions in the non omega-categorical case are envisaged.
Call for proposal
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