English

Undecidability of epimorphisms onto products of hyperbolic groups

Group Theory 2025-12-30 v1

Abstract

We exhibit examples of finitely presented subgroups PP of direct products of hyperbolic groups for which there is no algorithm that detects whether a finitely presented group has a quotient isomorphic to PP. For any torsion-free, linear, hyperbolic group QQ that maps onto the free group of rank 22 and m2m\geq 2, we construct a recursive sequence (Γn)nN(\Gamma_n)_{n\in \mathbb{N}} of torsion-free, hyperbolic C(16)C'(\frac{1}{6}) small cancellation groups, with the property that there is no algorithm determining the values nNn\in \mathbb{N} such that Γn\Gamma_n has a quotient isomorphic to the direct product QmQ^{m} of mm-copies of QQ.

Keywords

Cite

@article{arxiv.2512.22841,
  title  = {Undecidability of epimorphisms onto products of hyperbolic groups},
  author = {Konstantinos Tsouvalas},
  journal= {arXiv preprint arXiv:2512.22841},
  year   = {2025}
}

Comments

11 pages, Comments welcome