English

Thoma type results for discrete quantum groups

Quantum Algebra 2018-01-04 v2

Abstract

Thoma's theorem states that a group algebra C(Γ)C^*(\Gamma) is of type I if and only if Γ\Gamma is virtually abelian. We discuss here some similar questions for the quantum groups, our main result stating that, under suitable virtually abelianity conditions on a discrete quantum group Γ\Gamma, we have a stationary model of type π:C(Γ)MF(C(L))\pi:C^*(\Gamma)\to M_F(C(L)), with FF being a finite quantum group, and with LL being a compact group. We discuss then some refinements of these results in the quantum permutation group case, Γ^SN+\widehat{\Gamma}\subset S_N^+, by restricting the attention to the matrix models which are quasi-flat, in the sense that the images of the standard coordinates, known to be projections, have rank 1\leq1.

Keywords

Cite

@article{arxiv.1705.07050,
  title  = {Thoma type results for discrete quantum groups},
  author = {Teodor Banica and Alexandru Chirvasitu},
  journal= {arXiv preprint arXiv:1705.07050},
  year   = {2018}
}

Comments

20 pages

R2 v1 2026-06-22T19:52:42.419Z