Dorottya Sziráki (Alfréd Rényi Institute of Mathematics)

The open dihypergraph dichotomy and the Hurewicz dichotomy for generalized Baire spaces

Generalized descriptive set theory studies analogues, associated to uncountable regular cardinals $\kappa$, of well known topological spaces such as the real line, the Cantor space and the Baire space. A canonical example is the generalized Baire space ${}^\kappa\kappa$ of functions $f:\kappa\to\kappa$ equipped with the ${<}\kappa$-support topology.

The open graph dichotomy for a given set $X$ of reals is a strengthening of the perfect set property for $X$, and it can also be viewed as the definable version of the open coloring axiom restricted to $X$. Raphaël Carroy, Benjamin Miller and Dániel Soukup have recently introduced an $\aleph_0$-dimensional generalization of the open graph dichotomy which implies several well-known dichotomy theorems for Polish spaces.

We show that in Solovay's model, this $\aleph_0$-dimensional open dihypergraph dichotomy holds for all sets of reals. In our main theorem, we obtain a version of this previous result for generalized Baire spaces ${}^\kappa\kappa$ for uncountable regular cardinals $\kappa$. As an application, we derive several versions of the Hurewicz dichotomy for definable subsets of ${}^\kappa\kappa$. This is joint work with Philipp Schlicht.