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Preprint Number 423

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423. Dugald Macpherson, Katrin Tent
Pseudofinite groups with NIP theory and definability in finite simple groups

Submission date: 15 February 2012.


We show that any pseudofinite group with NIP theory and with a finite upper bound on the length of chains of centralisers is soluble-by-finite. In particular, any NIP rosy pseudofinite group is soluble-by-finite. This generalises, and shortens the proof of, an earlier result for stable pseudofinite groups. An example is given of an NIP pseudofinite group which is not soluble-by-finite. However, if C is a class of finite groups such that all infinite ultraproducts of members of C have NIP theory, then there is a bound on the index of the soluble radical of any member of C. We also survey some ways in which model theory gives information on families of finite simple groups, particularly concerning products of images of word maps.

Mathematics Subject Classification: 03C60

Keywords and phrases:

Full text arXiv 1202.3304: pdf, ps.

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