English

Sparse graphs and the fixed points on type spaces property

Logic 2024-08-14 v2

Abstract

We examine the topological dynamics of the automorphism groups of omega-categorical sparse graphs resulting from Hrushovski constructions. Specifically, we consider the fixed points on type spaces property, which a structure M has if, for each positive integer n, every Aut(M)-subflow of the space of n-types has a fixed point. Extending a result of Evans, Hubicka and Nesetril, we show that there exists an omega-categorical structure M, resulting from a Hrushovski construction, such that no omega-categorical expansion of M has the fixed points on type spaces property.

Keywords

Cite

@article{arxiv.2309.06829,
  title  = {Sparse graphs and the fixed points on type spaces property},
  author = {Rob Sullivan},
  journal= {arXiv preprint arXiv:2309.06829},
  year   = {2024}
}

Comments

Final version - accepted to Model Theory

R2 v1 2026-06-28T12:20:08.815Z