English

LCLs in the Borel Hierarchy

Logic 2026-01-28 v1 Combinatorics

Abstract

A locally checkable labeling problem (LCL) on a group Γ\Gamma asks one to find a labeling of the Cayley graph of Γ\Gamma satisfying a fixed, finite set of "local" constraints. Typical examples include proper coloring and perfect matching problems. In descriptive combinatorics, one often considers the existence of solutions to LCLs in the setting of descriptive set theory. For example, given a free action of Γ\Gamma on a Polish space XX, we might be interested in solving a given LCL on each orbit in a continuous, Borel, measurable, etc. way. In an attempt to understand more finely the gap between Borel and continuous combinatorics, we consider the existence of Baire class mm solutions to LCLs. For all n>1n > 1 and mωm \in \omega, we produce an LCL on Fn\mathbb{F}_n which always admits Baire class m+1m+1 solutions, but not necessarily Baire class mm solutions.

Keywords

Cite

@article{arxiv.2601.19046,
  title  = {LCLs in the Borel Hierarchy},
  author = {Felix Weilacher},
  journal= {arXiv preprint arXiv:2601.19046},
  year   = {2026}
}
R2 v1 2026-07-01T09:21:23.668Z