Maximal WAP and tame quotients of type spaces
Logic
2025-01-28 v1
Abstract
We study maximal WAP and tame (in the sense of topological dynamics) quotients of SX(C), where C is a sufficiently saturated (called monster) model of a complete theory T, X is a ∅-type-definable set, and SX(C) is the space of complete types over C concentrated on X. Namely, let FWAP⊆SX(C)×SX(C) be the finest closed, aut(C)-invariant equivalence relation on SX(C) such that the flow (aut(C),SX(C)/FWAP) is WAP, and let FTame⊆SX(C)×SX(C) be the finest closed, aut(C)-invariant equivalence relation on SX(C) such that the flow (aut(C),SX(C)/FTame) is tame. We show good behaviour of FWAP and FTame under changing the monster model C. Namely, we prove that if C′≻C is a bigger monster model, FWAP′ and FTame′ are the counterparts of FWAP and FTame computed for C′, and r:SX(C′)→SX(C) is the restriction map, then r[FWAP′]=FWAP and r[FTame′]=FTame. Using these results, we show that the Ellis (or ideal) groups of (aut(C),SX(C)/FWAP) and (aut(C),SX(C)/FTame) do not depend on the choice of the monster model C.
Cite
@article{arxiv.2501.15632,
title = {Maximal WAP and tame quotients of type spaces},
author = {Krzysztof Krupiński and Adrián Portillo},
journal= {arXiv preprint arXiv:2501.15632},
year = {2025}
}