On countable cofinality of definable chains in Borel partial orders

Abstract

We prove that in some cases definable chains of Borel partial orderings are necessarily countably cofinal. This includes the following cases: analytic chains, ROD chains in the Solovay model, and $\Sigma^1_2$ chains in the assumption that $\omega_1^{L[x]}<\omega_1$ for all reals $x$.