Metaplectic Casselman–Shalika conjecture

Let GG be the reductive group with coweight lattice Λ\Lambda, let Λ,+\Lambda^{\sharp,+} be the dominant metaplectic coweights, and let γΛ,+\gamma\in\Lambda^{\sharp,+} and μ,νΛ\mu,\nu\in\Lambda satisfy μ+νΛ+\mu+\nu\in\Lambda^+. Let C{\mathcal C} be the category of finite-dimensional representations of the corresponding big quantum group, let Wλ,!W^{\lambda,!} and Wλ,W^{\lambda,*} be its standard and costandard objects, and let Fr:Rep(Gˇζ)C\operatorname{Fr}:\operatorname{Rep}(\check G_\zeta)\to{\mathcal C} be the quantum Frobenius functor. The complex specified in the source by the referenced formula vanishes unless μΛ+\mu\in\Lambda^+. In the latter case, Metaplectic Casselman–Shalika conjecture. there is an isomorphism

c(GrBνGrGγ,(χμν)Lψ(sBν)AEγ)[ν,2ρˇ]DRHomD(C)(Wμ+ν,!,Wμ,Fr(V(γ))).\operatorname{R\Gamma}_c(\operatorname{Gr}_B^\nu\cap\overline{\operatorname{Gr}}_G^\gamma,(\chi_\mu^\nu)^*\mathcal L_\psi\otimes(s_B^\nu)^*\mathcal A_{\mathcal E}^\gamma)[\langle\nu,2\check\rho\rangle]\simeq\mathbb D\operatorname{RHom}_{\operatorname{D}({\mathcal C})}(W^{\mu+\nu,!},W^{\mu,*}\otimes\operatorname{Fr}(V(\gamma))).

This identifies the relevant metaplectic Whittaker cohomology with a derived Hom expression in the quantum-group category and is stated in the Casselman–Shalika section; the supplied text gives no resolution status.

Sources & referencesView supporting material

Primary source

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

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