Cohomological concentration conjecture for 0-toral characters

At least 3 years old · documented by

Let Tr\mathbb{T}_r and Ur\mathbb{U}_r be the groups appearing in the cohomology varieties YTr,UrY_{\mathbb{T}_r,\mathbb{U}_r}, and let θ ⁣:Tr(Fq)→F‾ℓ×\theta\colon \mathbb{T}_r(\mathbb{F}_q)\to\overline{\mathbb{F}}_\ell^{\times} be the reduction of a character θ~ ⁣:Tr(Fq)→Z‾ℓ×\widetilde{\theta}\colon \mathbb{T}_r(\mathbb{F}_q)\to\overline{\mathbb{Z}}_\ell^{\times}. The notation Hc∗(YTr,Ur;F‾ℓ)θH_c^*(Y_{\mathbb{T}_r,\mathbb{U}_r};\overline{\mathbb{F}}_\ell)_\theta denotes the corresponding character component of compactly supported étale cohomology, and a 0-toral character is understood in the sense of Cunningham–Osserman. Cohomological concentration conjecture. If θ\theta is a 0-toral character, then

Hc∗(YTr,Ur;F‾ℓ)θH_c^*(Y_{\mathbb{T}_r,\mathbb{U}_r};\overline{\mathbb{F}}_\ell)_\theta

is non-zero in only one degree. The conjecture extends known concentration results for ordinary Deligne–Lusztig varieties and is proposed in the context of torsion in integral cohomology; its resolution is not stated in the source.

References

Primary source

Gebhard Böckle, Tony Feng, Michael Harris, Chandrashekhar Khare and Jack A. Thorne, “Cyclic base change of cuspidal automorphic representations over function fields”, arXiv:2205.04499 (2023).

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.