On double-membership graphs of models of Anti-Foundation

Abstract

We answer some questions about graphs which are reducts of countable models of Anti-Foundation, obtained by considering the binary relation of double-membership $x\in y\in x$. We show that there are continuum-many such graphs, and study their connected components. We describe their complete theories and prove that each has continuum-many countable models, some of which are not reducts of models of Anti-Foundation.

arXiv comment15 pages, 2 figures

References in corpus (1)

• Undirecting membership in models of ZFA