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Wydział Matematyki, Informatyki i Mechaniki Uniwersytetu Warszawskiego

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Sem. Topologia i T. Mnogości

 

Large conjugacy classes and weak amalgamation


Prelegent: Maciej Malicki

2022-01-12 16:15

Ivanov, and later Kechris and Rosendal, characterized the existence of dense or comeager (diagonal) conjugacy classes in automorphism groups of certain classes of Fraïssé limits. I will show how these results can be extended to limits of weak Fraïssé classes, using an approach developed by Krawczyk and Kubiś. I will discuss homogenizability of weak Fraïssé classes, i.e., existence of a definable expansion to a Fraïssé class. I will also examine automorphism groups of ordered Fraïssé classes with the question in mind whether there exists a non-archimedean extremely amenable group with ample generics.

 

Please note that the seminar will take place in lecture hall 4420.