English

Indiscrete Common Commensurators

Group Theory 2023-10-11 v2

Abstract

We develop a framework for common commensurators of discrete subgroups of lattices in isometry groups of CAT(0) spaces. We show that the Greenberg-Shalom hypothesis about discreteness of common commensurators of Zariski dense subgroups and lattices fails in this generality, even if one imposes strong finiteness conditions. We analyze some examples due to Burger and Mozes in this context and show that they have discrete common commensurator.

Cite

@article{arxiv.2310.04876,
  title  = {Indiscrete Common Commensurators},
  author = {Jingyin Huang and Mahan Mj},
  journal= {arXiv preprint arXiv:2310.04876},
  year   = {2023}
}

Comments

20pgs no figures

R2 v1 2026-06-28T12:43:29.845Z