Lück's homological torsion growth conjecture for aspherical manifolds

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Let MM be an aspherical closed manifold. Consider a descending chain of subgroups

π1(M)=G0⊇G1⊇G2⊇⋯\pi_1(M)=G_0\supseteq G_1\supseteq G_2\supseteq\cdots

such that each GiG_i is normal in G=π1(M)G=\pi_1(M), the index [G:Gi][G:G_i] is finite, and ⋂i≥0Gi={1}\bigcap_{i\geq 0}G_i=\{1\}. Let p ⁣:M‾→Mp\colon\overline{M}\to M be the universal covering and put M[i]:=Gi\M‾M[i]:=G_i\backslash\overline{M}. Thus p[i] ⁣:M[i]→Mp[i]\colon M[i]\to M is a [G:Gi][G:G_i]-sheeted covering. Homological torsion growth conjecture. For every natural number nn with 2n+1≠dim⁡(M)2n+1\neq\dim(M),

lim⁡i→∞ln⁡(∣tors⁡(Hn(M[i];Z))∣)[G:Gi]=0.\lim_{i\to\infty}\frac{\ln\bigl(\lvert\operatorname{tors}(H_n(M[i];\mathbb{Z}))\rvert\bigr)}{[G:G_i]}=0.

If dim⁡(M)=2m+1\dim(M)=2m+1 is odd, then M~\widetilde{M} is det⁡\det-L2L^2-acyclic and

lim⁡i→∞ln⁡(∣tors⁡(Hm(M[i];Z))∣)[G:Gi]=(−1)mρ(2)(M~).\lim_{i\to\infty}\frac{\ln\bigl(\lvert\operatorname{tors}(H_m(M[i];\mathbb{Z}))\rvert\bigr)}{[G:G_i]}=(-1)^m\rho^{(2)}(\widetilde{M}).

This conjecture is a homological approximation statement relating normalized torsion growth in finite covers to L2L^2-torsion; for locally symmetric spaces it reduces to a conjecture of Bergeron and Venkatesh. Its general status is unresolved.

References

Primary source

Sam Hughes and Wolfgang Lueck, “L^2-torsion of automorphisms”, arXiv:2510.20959 (2026).

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