English

Torsion-Free Abelian Groups are Borel Complete

Logic 2023-02-22 v6 Group Theory

Abstract

We prove that the Borel space of torsion-free Abelian groups with domain ω\omega is Borel complete, i.e., the isomorphism relation on this Borel space is as complicated as possible, as an isomorphism relation. This solves a long-standing open problem in descriptive set theory, which dates back to the seminal paper on Borel reducibility of Friedman and Stanley from 1989.

Keywords

Cite

@article{arxiv.2102.12371,
  title  = {Torsion-Free Abelian Groups are Borel Complete},
  author = {Gianluca Paolini and Saharon Shelah},
  journal= {arXiv preprint arXiv:2102.12371},
  year   = {2023}
}
R2 v1 2026-06-23T23:28:42.311Z