Relative primeness and Borel partition properties for equivalence relations

TL;DR

This paper introduces the concept of relative primeness for equivalence relations, strengthening non-reducibility, and explores Borel partition properties, including Borel weak compactness, for standard benchmark relations.

Contribution

It develops the notion of relative primeness for equivalence relations and extends Borel partition properties, providing new characterizations and frameworks for analyzing Borel reducibility.

Findings

Relative primeness strengthens non-reducibility for many benchmark relations.

Introduces Borel weak compactness and characterizes partition properties for specific equivalence relations.

Discusses dichotomies and frameworks for Borel reducibility questions.

Abstract

We introduce a notion of relative primeness for equivalence relations, strengthening the notion of non-reducibility, and show for many standard benchmark equivalence relations that non-reducibility may be strengthened to relative primeness. We introduce several analogues of cardinal properties for Borel equivalence relations, including the notion of a prime equivalence relation and Borel partition properties on quotient spaces. In particular, we introduce a notion of Borel weak compactness, and characterize partition properties for the equivalence relations ${\mathbb F}_2$ and ${\mathbb E}_1$. We also discuss dichotomies related to primeness, and see that many natural questions related to Borel reducibility of equivalence relations may be viewed in the framework of relative primeness and Borel partition properties.