Cardinal Characteristics of Models of Set Theory

Douglas Ulrich

Published 2018-11-13Version 1

We continue our investigation =of Shelah's interpretability orders $\trianglelefteq^*_\kappa$ as well as the new orders $\trianglelefteq^\times_\kappa$. In particular, we give streamlined proofs of the existence of minimal unstable, unsimple and nonlow theories in these orders, and we give a similar analysis of the hypergraph examples $T_{n, k}$ of Hrushovski. We also prove that if $\mathcal{B}$ is a complete Boolean algebra with the $\lambda$-c.c., then no nonprincipal ultrafilter on $\mathcal{U}$ $\lambda^+$-saturates any unsimple theory.