Popa's W*-superrigidity conjecture for property (T) groups

From papers

Let GG be an ICC group with property (T), let HH be a group, and let L(G)\operatorname{L}(G) and L(H)\operatorname{L}(H) denote their group von Neumann algebras. An isomorphism L(G)L(H)\operatorname{L}(G)\cong\operatorname{L}(H) is said to be induced by a character GTG\to\mathbb T and a group isomorphism GHG\to H up to conjugation by a unitary element when it has that form. Popa's conjecture. For any such GG and HH, every isomorphism

L(G)L(H)\operatorname{L}(G)\cong\operatorname{L}(H)

is induced by a character GTG\to\mathbb T and a group isomorphism GHG\to H, up to conjugation by a unitary element. This generalizes Connes' rigidity conjecture and incorporates Jones' formula for outer automorphisms. The statement is presented as a conjectural strengthening for property (T) groups; no resolution is given here.

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Sources & referencesView supporting material

Primary source

I. Chifan, A. Ioana, D. Osin and B. Sun, “Wreath-like products of groups and their von Neumann algebras II: Outer automorphisms”, arXiv:2304.07457 (2025).

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