English

Strongly solid ${\rm II_1}$ factors with an exotic MASA

Operator Algebras 2025-07-17 v3

Abstract

Using an extension of techniques of Ozawa and Popa, we give an example of a non-amenable strongly solid II1\rm{II}_1 factor MM containing an "exotic" maximal abelian subalgebra AA: as an AA,AA-bimodule, L2(M)L^2(M) is neither coarse nor discrete. Thus we show that there exist II1\rm{II}_1 factors with such property but without Cartan subalgebras. It also follows from Voiculescu's free entropy results that MM is not an interpolated free group factor, yet it is strongly solid and has both the Haagerup property and the complete metric approximation property.

Keywords

Cite

@article{arxiv.0904.1225,
  title  = {Strongly solid ${\rm II_1}$ factors with an exotic MASA},
  author = {Cyril Houdayer and Dimitri Shlyakhtenko},
  journal= {arXiv preprint arXiv:0904.1225},
  year   = {2025}
}

Comments

23 pages

R2 v1 2026-06-21T12:49:14.200Z