Transferring Symmetry

TL;DR

This paper demonstrates how to transfer symmetry properties from a larger cardinal to a smaller one in superstable abstract elementary classes using towers, without extra set-theoretic assumptions.

Contribution

It introduces a new application of towers to transfer symmetry from + to  in superstable AECs, expanding the tools for analyzing model-theoretic properties.

Findings

Symmetry for non-+-splitting implies symmetry for non--splitting.

Uses towers to transfer symmetry without extra set-theoretic assumptions.

Applicable to superstable AECs with amalgamation and joint embedding.

Abstract

In this paper, we apply results of \cite{Va3} and use towers to transfer symmetry from $\mu^+$ down to $\mu$ in superstable abstract elementary classes without using extra set-theoretic assumptions or tameness. Theorem. Suppose $\mathcal{K}$ is an abstract elementary class satisfying the amalgamation and joint embedding properties and that $\mathcal{K}$ is both $\mu$- and $\mu^+$-superstable. If $\mathcal{K}$ has symmetry for non-$\mu^+$-splitting, then $\mathcal{K}$ has symmetry for non-$\mu$-splitting. This is a new application of towers which were introduced by Shelah and Villaveces \cite{ShVi} and later used by VanDieren \cite{Va1}, \cite{Va2} and Grossberg, VanDieren, and Villaveces \cite{GVV} to prove the uniqueness of limit models.