Logic Seminar

We discuss a recent paper of Pequignot in which he answers a question of Kechris, Solecki, and Todorcevic concerning graphs generated by a single Borel function. It is shown that the shift graph on the space of infinite subsets of natural numbers does not admit a Borel homomorphism into every such graph with infinite Borel chromatic number. Notably, only definability arguments are used and no counterexample is produced.