English

Examples of W$^*$ and C$^*$-superrigid product groups

Operator Algebras 2026-02-06 v1

Abstract

We provide a new large class CAFP\mathcal C_{AFP} of amalgamated free product groups for which the product rigidity result from [CdSS15] holds: if G1,,GnCAFPG_1,\dots,G_n\in\mathcal C_{AFP} and HH is any group such that L(G1××Gn)L(H)L(G_1\times\dots\times G_n)\cong L(H), then there exists a product decomposition H=H1××HnH=H_1\times\dots\times H_n such that L(Hi)L(H_i) is stably isomorphic to L(Gi)L(G_i), for any 1in1\leq i\leq n. The class CAFP\mathcal C_{AFP} contains WW^* and CC^*-superrigid groups from [CD-AD20]. Consequently, we obtain examples of product groups that are both WW^* and CC^*-superrigid.

Cite

@article{arxiv.2602.05618,
  title  = {Examples of W$^*$ and C$^*$-superrigid product groups},
  author = {Jakub Curda and Daniel Drimbe},
  journal= {arXiv preprint arXiv:2602.05618},
  year   = {2026}
}
R2 v1 2026-07-01T09:37:49.927Z