Stability conjecture for Steinberg-module homology of congruence subgroups

Let pp be a prime. Let VBZ/Γ(p)\mathrm{VB}_{\mathbb{Z}}/\Gamma(p) denote the indicated module category, let \mathbfitAΓ(p)\mathbfit{A}_{\Gamma(p)} be its apartment algebra, let k\Bbbk be the coefficient module, and let St\mathbf{St} be the Steinberg module. For integers i,j0i,j\geq 0, consider

Tori\mathbfitAΓ(p)(k,Hj(Γ(p);St)).\operatorname{Tor}^{\mathbfit{A}_{\Gamma(p)}}_i\bigl(\Bbbk,\operatorname{H}_j(\Gamma(p);\mathbf{St})\bigr).

Steinberg-module stability conjecture. For each i,j0i,j\geq 0, the VBZ/Γ(p)\mathrm{VB}_{\mathbb{Z}}/\Gamma(p)-module

Tori\mathbfitAΓ(p)(k,Hj(Γ(p);St))\operatorname{Tor}^{\mathbfit{A}_{\Gamma(p)}}_i\bigl(\Bbbk,\operatorname{H}_j(\Gamma(p);\mathbf{St})\bigr)

is supported in finitely many degrees.

The conjecture is presented as a precise form of the expected representation stability for congruence-subgroup homology with Steinberg coefficients. The paper proves it for p=3p=3, j=0j=0, and all ii, while the general assertion remains open.

Sources & referencesView supporting material

Primary source

Jeremy Miller, Rohit Nagpal and Peter Patzt, “Stability in the high-dimensional cohomology of congruence subgroups”, arXiv:1806.11131 (2020).

Progress summary

Never refreshed

Nothing recorded yet. Refresh searches the literature and the public web for attempts on this problem, and writes the first summary here.

Solutions 0

No solutions have been posted yet.