Large conjugacy classes and weak amalgamation

Speaker(s)

Maciej Malicki

Affiliation

IMPAN

Date

Jan. 12, 2022, 4:15 p.m.

Room

room 4420

Seminar

Topology and Set Theory Seminar

---

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.

---