Countable models of the theories of Baldwin-Shi hypergraphs and their regular types
Abstract
We continue the study of the theories of Baldwin-Shi hypergraphs from . Restricting our attention to when the rank is rational valued, we show that each countable model of the theory of a given Baldwin-Shi hypergraph is isomorphic to a generic structure built from some suitable subclass of the original class of finite structures with the inherited notion of strong substructure. We introduce a notion of dimension for a model and show that there is a an elementary chain of countable models of the theory of a fixed Baldwin-Shi hypergraph with if and only if the dimension of is at most the dimension of and that each countable model is isomorphic to some . We also study the regular types that appear in these theories and show that the dimension of a model is determined by a particular regular type. Further, drawing on the work of Brody and Laskowski, we use these structures to give an example of a pseudofinite, -stable theory with a non-locally modular regular type, answering a question of Pillay in .
Keywords
Cite
@article{arxiv.1804.00932,
title = {Countable models of the theories of Baldwin-Shi hypergraphs and their regular types},
author = {Danul K. Gunatilleka},
journal= {arXiv preprint arXiv:1804.00932},
year = {2018}
}
Comments
12 pages