Kottwitz's multiplicity conjecture for global rigid inner forms

Let GG be a connected reductive group over a global function field FF, let φ\varphi range over the global parameters for GG, and let Πφ\Pi_\varphi be the conjectural global LL-packet arising from a coherent family of local representations of rigid inner forms. For πΠφ\pi\in\Pi_\varphi, let Sφ\mathcal{S}_\varphi be the finite group associated with the centralizer of φ\varphi, let , ⁣:Sφ×ΠφC\langle-,-\rangle\colon\mathcal{S}_\varphi\times\Pi_\varphi\to\mathbb{C} be the conjectural pairing, and define

m(φ,π):=Sφ1xSφx,π.m(\varphi,\pi):=|\mathcal{S}_\varphi|^{-1}\sum_{x\in\mathcal{S}_\varphi}\langle x,\pi\rangle.

Kottwitz's multiplicity conjecture. The multiplicity of π\pi in the discrete spectrum of GG is given by

φm(φ,π),\sum_{\varphi}m(\varphi,\pi),

where the sum is over all φ\varphi such that πΠφ\pi\in\Pi_\varphi. This is the proposed global multiplicity formula for coherent rigid inner forms; the source supplies no evidence that it has been proved or refuted.

Sources & referencesView supporting material

Primary source

Peter Dillery, “Rigid inner forms over global function fields”, arXiv:2110.10820 (2025).

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