Cuspidality conjecture for the categorical local Langlands correspondence

Let GG be a reductive group, let B(G)basB(G)_{\operatorname{bas}} denote the basic σ\sigma-conjugacy classes, and let GbG_b be the extended pure inner form corresponding to bB(G)basb\in B(G)_{\operatorname{bas}}. Write ib ⁣:BunGb=[/Gb(E)]BunGi^b\colon \operatorname{Bun}_G^b=[\ast/G_b(E)]\hookrightarrow \operatorname{Bun}_G for the open immersion, and let CTP\operatorname{CT}_P be the normalized geometric constant term functor for a parabolic subgroup PP of GG. Define Dlis(BunG,Q)cusp\mathcal{D}_{\operatorname{lis}}(\operatorname{Bun}_G,\overline{\mathbb{Q}}_\ell)_{\operatorname{cusp}} as the subcategory of objects AA such that CTP(A)=0\operatorname{CT}_P(A)=0 for every proper parabolic subgroup PP of GG. Cuspidality conjecture. The inclusion

Dlis(BunG,Q)[G]Dlis(BunG,Q)cusp\mathcal{D}_{\operatorname{lis}}(\operatorname{Bun}_G,\overline{\mathbb{Q}}_\ell)_{[G]}\subset \mathcal{D}_{\operatorname{lis}}(\operatorname{Bun}_G,\overline{\mathbb{Q}}_\ell)_{\operatorname{cusp}}

is an equality. In particular, for every smooth irreducible Q\overline{\mathbb{Q}}_\ell-representation π\pi of Gb(E)G_b(E), its Fargues--Scholze parameter φπFS\varphi^{\operatorname{FS}}_\pi is supercuspidal if and only if

CTP(i!bπ)=0\operatorname{CT}_P(i^b_!\pi)=0

for every proper parabolic subgroup PP of GG. This conjecture identifies the categorical [G][G]-part with the cuspidal subcategory and predicts a corresponding characterization of supercuspidal Fargues--Scholze parameters. The inclusion is established in the source; the converse, and hence the equality, is conjectural.

Sources & referencesView supporting material

Primary source

Yuta Takaya, “Second adjointness and cuspidal supports at the categorical level”, arXiv:2408.04582 (2024).

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