Geometric Broué's abelian defect conjecture

Let \ell be a prime and let G=G(q)G=\mathbb{G}(q) be a finite group of Lie type, where pp\ne\ell and qq is a power of pp. Let DSyl(G)D\in\operatorname{Syl}_{\ell}(G), let (K,O,k)(K,\mathcal{O},k) be an \ell-modular system, and put H=NG(D)H=N_G(D). Let dd be the order of qq modulo \ell, and let κ\kappa be coprime to dd. Geometric Broué's abelian defect conjecture. There exists a Deligne–Lusztig variety Yκ/dY_{\kappa/d}, with GG acting on the right and CG(D)C_G(D) acting on the left, such that the action of CG(D)C_G(D) extends to HH, every unipotent character χUch(B0(G))\chi\in\operatorname{Uch}(B_0(G)) occurs in a unique cohomology group Hi(Yκ/d,K)H^i(Y_{\kappa/d},K), the complex C=RΓ(Yκ/d,k)C=R\Gamma(Y_{\kappa/d},k) induces a perverse equivalence between B0(G)B_0(G) and B0(H)B_0(H), and the associated perversity function is obtained from the cohomological degree map via a suitable bijection between Uch(B0(G))\operatorname{Uch}(B_0(G)) and SB0(H)\mathcal{S}_{B_0(H)}. The source presents this combined geometric statement as open, with only restricted cases known.

Sources & referencesView supporting material

Primary source

Stefano Sannella, “An algorithmic approach to perverse derived equivalences: Broué's Conjecture for Ω^+_8(2)”, arXiv:1810.01467 (2019).

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