English

Maximal discrete subgroups in unitary groups of operator algebras

Operator Algebras 2026-04-28 v1

Abstract

We show that if a group G is mixed-identity-free, then the projective unitary group of its group von Neumann algebra contains a maximal discrete subgroup containing G. The proofs are elementary and make use of free probability theory. In addition, we clarify the situation for C*-algebras.

Keywords

Cite

@article{arxiv.2206.06704,
  title  = {Maximal discrete subgroups in unitary groups of operator algebras},
  author = {Vadim Alekseev and Andreas Thom},
  journal= {arXiv preprint arXiv:2206.06704},
  year   = {2026}
}

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9 pages