The restriction conjecture for local Langlands packets of disconnected groups

Let BAB\to A be a map of finite groups acting on a connected reductive group GG, and write GA=GAG^A=G\rtimes A and GB=GBG^B=G\rtimes B. Let πA\pi^A correspond to (ϕ,ρA)(\phi,\rho^A) for GzA(F)G^A_z(F) and let πB\pi^B correspond to (ϕ,ρB)(\phi',\rho^B) for GzB(F)G^B_z(F). The restriction conjecture. The multiplicity of πB\pi^B in the restriction of πA\pi^A to GzB(F)G^B_z(F) is zero unless ϕ\phi and ϕ\phi' are GAG^A-equivalent. After choosing equivalent representatives with ϕ=ϕ\phi=\phi', this multiplicity equals the multiplicity of ρB\rho^B in the restriction of ρA\rho^A to the corresponding component group. This predicts compatibility of the local correspondence with restriction along maps of component groups; it remains conjectural in the stated generality.

Sources & referencesView supporting material

Primary source

Tasho Kaletha, “On the local Langlands conjectures for disconnected groups”, arXiv:2210.02519 (2026).

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