Most(?) theories have Borel complete reducts (2103.09724v2)

Abstract: We prove that many seemingly simple theories have Borel complete reducts. Specifically, if a countable theory has uncountably many complete 1-types, then it has a Borel complete reduct. Similarly, if $Th(M)$ is not small, then $M^{eq}$ has a Borel complete reduct, and if a theory $T$ is not $\omega$-stable, then the elementary diagram of some countable model of $T$ has a Borel complete reduct.