The subtop cohomology conjecture for metaplectic Whittaker models

Let ρ\rho be the quadratic form on the coweight lattice associated with the metaplectic data. For cˉ\bar c the residue-field point and θˉ\bar\theta the image of θ\theta in the adjoint coweight lattice, let θ\theta range over simple coroots. Assume

ϱ(αi)Z\varrho(\alpha_i)\notin \mathbb{Z}

for every simple coroot αi\alpha_i. The subtop cohomology property is the condition that, for every positive coweight λ\lambda that is not a simple coroot, the compactly supported cohomology complex

c(GrB0GrBλ,sλLG)\operatorname{R\Gamma}_c(\operatorname{Gr}_B^0\cap \operatorname{Gr}_{B^-}^{-\lambda},s_{-\lambda}^*\mathcal L_G)

is concentrated in degrees at most λ,2ρˇ2\langle\lambda,2\check\rho\rangle-2. Subtop cohomology conjecture. If ϱ(αi)Z\varrho(\alpha_i)\notin\mathbb{Z} for every simple coroot αi\alpha_i, then the subtop cohomology property is satisfied for ϱ\varrho. The property is used to control the subtop cohomology of metaplectic Whittaker sheaves; the supplied text gives no resolution status beyond this asserted statement.

Sources & referencesView supporting material

Primary source

Sergey Lysenko, “Twisted Whittaker models for metaplectic groups”, arXiv:1509.02433 (2017).

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