The relative solidity conjecture for relatively hyperbolic groups

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Let GG be a group that is hyperbolic relative to a finite family of subgroups {H1,…,Hn}\{H_1,\ldots,H_n\}. Denote by M=L(G)\mathcal M=\mathcal L(G) the von Neumann algebra corresponding to GG. Let p∈Mp\in\mathcal M be a nonzero projection and let A⊆pMp\mathcal A\subseteq p\mathcal M p be a von Neumann subalgebra whose relative commutant A′∩pMp\mathcal A'\cap p\mathcal M p has no amenable direct summand. Relative solidity conjecture. There is some 1≤i≤n1\leq i\leq n such that a corner of A\mathcal A intertwines into L(Hi)\mathcal L(H_i) inside M\mathcal M, in the sense of Popa; that is, A≺ML(Hi)\mathcal A\prec_{\mathcal M}\mathcal L(H_i). This concerns the structure of commuting subalgebras of group von Neumann algebras associated with relatively hyperbolic groups; the supplied text gives no resolution status for the conjecture.

References

Primary source

Juan Felipe Ariza Mejia, Dulanji Nikethani Amaraweera, Ionut Chifan and Krishnendu Khan, “Relative solidity results and their applications to computations of some II_1 factor invariants”, arXiv:2509.19481 (2025).

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