Commutation of the nonabelian Fourier transforms on elliptic unipotent representations

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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 FT⁡ell∨\operatorname{FT}^{\vee}_{\mathsf{ell}} be the Fourier transform on the elliptic unipotent side, let res⁡unpar\operatorname{res}^{\mathsf{par}}_{\mathsf{un}} and res⁡unK0\operatorname{res}^{K_0}_{\mathsf{un}} be restriction maps to the unipotent representations of parahoric quotients, and let proj⁡ellpar\operatorname{proj}^{\mathsf{par}}_{\mathsf{ell}} be projection to the elliptic parahoric space. Write FT⁡par\operatorname{FT}^{\mathsf{par}} for the parahoric Fourier transform and FT⁡K0\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:

proj⁡ellpar∘res⁡unpar∘FT⁡ell∨=proj⁡ellpar∘FT⁡par∘res⁡par.\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

res⁡unK0∘FT⁡ell∨=FT⁡K0∘res⁡unK0.\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.

References

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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