Simple Homogeneous Structures and Indiscernible Sequence Invariants
Abstract
We introduce some properties describing dependence in indiscernible sequences: and its dual , the definable Morley property, and -resolvability. Applying these properties, we establish the following results: We show that the degree of nonminimality introduced by Freitag and Moosa, which is closely related to (equal in ), may take on any positive integer value in an -stable theory, answering a question of Freitag, Jaoui, and Moosa. Proving a conjecture of Koponen, we show that every simple theory with quantifier elimination in a finite relational language has finite rank and is one-based. The arguments closely rely on finding types with , and on -resolvability. We prove some variants of the simple Kim-forking conjecture, a generalization of the stable forking conjecture to theories. We show a global analogue of the simple Kim-forking conjecture with infinitely many variables holds in every theory, and show that Kim-forking with a realization of a type with satisfies a finite-variable version of this result. We then show, in a low theory or when is isolated, if has the definable Morley property for Kim-independence, Kim-forking with realizations of gives a nontrivial instance of the simple Kim-forking conjecture itself. In particular, when and , Kim-forking with realizations of gives us a nontrivial instance of the simple Kim-forking conjecture. We show that the quantity , motivated in simple and theories by the above results, is in fact nontrivial even in stable theories.
Cite
@article{arxiv.2405.08211,
title = {Simple Homogeneous Structures and Indiscernible Sequence Invariants},
author = {John Baldwin and James Freitag and Scott Mutchnik},
journal= {arXiv preprint arXiv:2405.08211},
year = {2026}
}
Comments
63 pages