English

Pointlike sets for varieties determined by groups

Group Theory 2018-01-16 v1 Formal Languages and Automata Theory

Abstract

For a variety of finite groups H\mathbf H, let H\overline{\mathbf H} denote the variety of finite semigroups all of whose subgroups lie in H\mathbf H. We give a characterization of the subsets of a finite semigroup that are pointlike with respect to H\overline{\mathbf H}. Our characterization is effective whenever H\mathbf H has a decidable membership problem. In particular, the separation problem for H\overline{\mathbf H}-languages is decidable for any decidable variety of finite groups H\mathbf H. This generalizes Henckell's theorem on decidability of aperiodic pointlikes.

Keywords

Cite

@article{arxiv.1801.04638,
  title  = {Pointlike sets for varieties determined by groups},
  author = {Samuel J. v. Gool and B. Steinberg},
  journal= {arXiv preprint arXiv:1801.04638},
  year   = {2018}
}
R2 v1 2026-06-22T23:44:53.449Z