Artin–Deligne duality conjecture for Arthur packets

From papers

Let GG be a quasi-split connected reductive group over a local or global field FF. For a parameter ψ\mathfrak{\psi}, let mathitPiψ(G)Amathit{Pi}_{\mathfrak{\psi}}(G)^A and mathitPiψ(G)Dmathit{Pi}_{\mathfrak{\psi}}(G)^D denote the Arthur packets defined using Artin's and Deligne's conventions, respectively; let w\mathfrak{w} be a Whittaker datum, Sψ\mathcal{S}_{\mathfrak{\psi}} the component group, and C^\widehat C the relevant duality automorphism. Artin–Deligne duality conjecture. Locally,

mathitPiψ(G)D=(mathitPiψ(G)A)=mathitPiψ(G)A,mathit{Pi}_{\mathfrak{\psi}}(G)^D=(mathit{Pi}_{\mathfrak{\psi}}(G)^A)^\vee=mathit{Pi}_{\mathfrak{\psi}^\vee}(G)^A,

and, for mathitpi\inmathitPiψ(G)Dmathit{pi}\inmathit{Pi}_{\mathfrak{\psi}}(G)^D and x\inmathcalSψx\inmathcal{S}_{\mathfrak{\psi}},

pi,xw,ψD=pi,x1w1,ψA=pi,C^1(x)w,ψA.\langle\mathit{pi},x\rangle^D_{\mathfrak{w},\mathfrak{\psi}}=\langle\mathit{pi}^\vee,x^{-1}\rangle^A_{\mathfrak{w}^{-1},\mathfrak{\psi}}=\langle\mathit{pi},\widehat C^{-1}(x)\rangle^A_{\mathfrak{w},\mathfrak{\psi}^\vee}.

Globally,

Lψ2(G)D=(Lψ2(G)A)=Lψ2(G)A,m(pi,ψ)=m(pi,ψ).L^2_{\mathfrak{\psi}}(G)^D=(L^2_{\mathfrak{\psi}}(G)^A)^\vee=L^2_{\mathfrak{\psi}^\vee}(G)^A, \qquad m(\mathit{pi}^\vee,\mathfrak{\psi}^\vee)=m(\mathit{pi},\mathfrak{\psi}).

This conjecture predicts compatibility between Artin and Deligne normalizations, contragredient representations, dual parameters, packet pairings, and global multiplicities. The source gives no resolution status.

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Sources & referencesView supporting material

Primary source

Hiraku Atobe, Wee Teck Gan, Atsushi Ichino, Tasho Kaletha, Alberto Mínguez and Sug Woo Shin, “Local Intertwining Relations and Co-tempered A-packets of Classical Groups”, arXiv:2410.13504 (2026).

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