Lück's determinant conjecture for all discrete groups

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Let Γ\Gamma be a discrete group, let L(Γ)L(\Gamma) be its group von Neumann algebra, and let τ\tau be the standard trace on L(Γ)L(\Gamma). For A∈Mn(Z[Γ])A\in M_n(\mathbb{Z}[\Gamma]), write

ln⁡+(t)={0t=0,ln⁡(t)t>0,\ln_+(t)=\begin{cases}0 & t=0,\\ \ln(t) & t>0,\end{cases}

and let tr⁡n\operatorname{tr}_n denote the normalized trace on Mn(C)M_n(\mathbb{C}). The group Γ\Gamma satisfies Lück's determinant conjecture when

(τ⊗tr⁡n)(ln⁡+(A∗A))≥0(\tau\otimes\operatorname{tr}_n)\bigl(\ln_+(A^*A)\bigr)\geq 0

for every A∈Mn(Z[Γ])A\in M_n(\mathbb{Z}[\Gamma]) and every n∈Nn\in\mathbb{N}. Lück's determinant conjecture. Every discrete group satisfies Lück's determinant conjecture. The quantity is the logarithm of the modified Fuglede–Kadison determinant, obtained by ignoring zero singular values. The conjecture asks whether this determinant inequality holds universally for groups; the source presents it as an open possibility and motivates its extension to invariant random subgroups, where determinant-conjecture examples exist that are not co-sofic.

References

Primary source

Aareyan Manzoor, “Invariant Random Subgroups, Soficity, and Lück's determinant conjecture”, arXiv:2508.15154 (2025).

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