Borel's pullback conjecture for enhanced local Langlands correspondences

Let d4a2~\tilde{d4a2} and d4a2d4a2 be connected reductive FF-groups, and let d45d4a2d4a2d4a2d45 d4a2d4a2d4a2 be a homomorphism satisfying Condition 1: the kernel of its differential is central and its cokernel is a commutative FF-group. Let d4a2d4a2 and G~\tilde G be the corresponding groups of FF-points, let d4a2Lηd4a2^L\eta be a dual L-homomorphism, and let Sη:C[Sϕ]C[SLηϕ]{}^S\eta:\mathbb C[\mathcal S_\phi]\to\mathbb C[\mathcal S_{{}^L\eta\circ\phi}] be the associated algebra homomorphism. For an enhanced parameter (ϕ,ρ)Φe(G)(\phi,\rho)\in\Phi_e(G), write π(ϕ,ρ)\pi(\phi,\rho) for the corresponding representation.

Borel's pullback conjecture. Suppose that a local Langlands correspondence exists for sufficiently large classes of representations of GG and G~\tilde G. Then

η(π(ϕ,ρ))=ρ~Irr(SLηϕ)HomSϕ(ρ,Sη(ρ~))π(Lηϕ,ρ~).\eta^*(\pi(\phi,\rho))=\bigoplus_{\tilde\rho\in\operatorname{Irr}(\mathcal S_{{}^L\eta\circ\phi})}\operatorname{Hom}_{\mathcal S_\phi}\bigl(\rho,{}^S\eta^*(\tilde\rho)\bigr)\otimes\pi({}^L\eta\circ\phi,\tilde\rho).

This predicts the decomposition of pullback representations under a functorial local Langlands correspondence; the source gives no resolution status.

Sources & referencesView supporting material

Primary source

Maarten Solleveld, “Langlands parameters, functoriality and Hecke algebras”, arXiv:1810.12693 (2019).

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