Commutation of the nonabelian Fourier transforms on elliptic unipotent representations

Let GG be the reductive pp-adic group and let Run,ell\mathsf{R}_{\mathsf{un},\mathsf{ell}} denote its elliptic unipotent representation space. Let FTell\operatorname{FT}^{\vee}_{\mathsf{ell}} be the Fourier transform on the elliptic unipotent side, let resunpar\operatorname{res}^{\mathsf{par}}_{\mathsf{un}} and resunK0\operatorname{res}^{K_0}_{\mathsf{un}} be restriction maps to the unipotent representations of parahoric quotients, and let projellpar\operatorname{proj}^{\mathsf{par}}_{\mathsf{ell}} be projection to the elliptic parahoric space. Write FTpar\operatorname{FT}^{\mathsf{par}} for the parahoric Fourier transform and FTK0\operatorname{FT}^{K_0} for the transform associated with a maximal hyperspecial parahoric K0K_0. Commutation conjecture. The two Fourier transforms commute on the elliptic space:

projellparresunparFTell=projellparFTparrespar.\operatorname{proj}^{\mathsf{par}}_{\mathsf{ell}}\circ \operatorname{res}^{\mathsf{par}}_{\mathsf{un}}\circ \operatorname{FT}^{\vee}_{\mathsf{ell}}=\operatorname{proj}^{\mathsf{par}}_{\mathsf{ell}}\circ \operatorname{FT}^{\mathsf{par}}\circ \operatorname{res}^{\mathsf{par}}.

Moreover, if K0K_0 is the maximal hyperspecial parahoric of GG, then on the elliptic subspace Run(G)ellR_{\mathsf{un}}(G)_{\mathsf{ell}} one has

resunK0FTell=FTK0resunK0.\operatorname{res}^{K_0}_{\mathsf{un}}\circ \operatorname{FT}^{\vee}_{\mathsf{ell}}=\operatorname{FT}^{K_0}\circ \operatorname{res}^{K_0}_{\mathsf{un}}.

This expected compatibility would relate the nonabelian Fourier transform for elliptic unipotent representations of the pp-adic group to the Fourier transforms for finite reductive quotients of parahoric subgroups. The supplied text gives no resolution, so the conjecture remains open.

Sources & referencesView supporting material

Primary source

Dan Ciubotaru, “The nonabelian Fourier transform for elliptic unipotent representations of exceptional p-adic groups”, arXiv:2006.13540 (2020).

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