The type II ring-isomorphism conjecture for locally measurable operator algebras

Let MM and NN be von Neumann algebras of type II. Let LS(M)LS(M) and LS(N)LS(N) denote their algebras of locally measurable operators. A ring isomorphism is a bijective ring homomorphism Ψ ⁣:LS(M)LS(N)\Psi\colon LS(M)\to LS(N). A real ^*-isomorphism is a bijective real-linear ^*-preserving algebra homomorphism. The type II ring-isomorphism conjecture. If Ψ ⁣:LS(M)LS(N)\Psi\colon LS(M)\to LS(N) is a ring isomorphism, then there exist an invertible operator yLS(N)y\in LS(N) and a real ^*-isomorphism ψ ⁣:MN\psi\colon M\to N such that

Ψ(x)=yψ(x)y1\Psi(x)=y\psi(x)y^{-1}

for any xLS(M)x\in LS(M). The conjecture extends the corresponding result for von Neumann algebras of type I\mathrm{I}_\infty or III. The source notes that little is known about the structure of LS(M)LS(M) for type II algebras and that even automatic real-linearity of such ring isomorphisms is unknown, including for approximately finite-dimensional type II1_1 factors.

Sources & referencesView supporting material

Primary source

Michiya Mori, “Lattice isomorphisms between projection lattices of von Neumann algebras”, arXiv:2006.08959 (2020).

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