Logic Seminar
Greg Hjorth
University of California at Los Angeles
Treeable equivalence relations
Abstract: An equivalence relation $E$ on $X$ is treeable if there is an acyclic graph $R$ which is Borel as a subset of
$X\times X$ and whose connected components form the $E$-equivalence classes.
I will survey what is known about treeable equivalence relations up to Borel reducibility and orbit
equivalence. I will also mention a dichotomy theorem for when a treeable equivalence relation is reducible
to one with countable classes and another dichotomy theorem for when it is possible to select an end
from each equivalence class.
Tuesday September 6, 2005 at 4:00 PM in SEO 427