English

Definably amenable groups in Continuous logic

Logic 2025-04-03 v3

Abstract

We introduce the notions of definable amenability and extreme definable amenability for groups in continuous structures and conduct an extensive analysis of them, drawing parallels with the classical first-order case. We characterize both notions using fixed-point properties. We show that stable and ultracompact groups are definably amenable and prove that, for groups definable in dependent theories, definable amenability is equivalent to the existence of an f-generic type. Finally, we show the randomizations of first-order definably amenable groups are extremely definably amenable.

Keywords

Cite

@article{arxiv.2201.09971,
  title  = {Definably amenable groups in Continuous logic},
  author = {Juan Felipe Carmona and Alf Onshuus},
  journal= {arXiv preprint arXiv:2201.09971},
  year   = {2025}
}