Artin–Deligne duality conjecture for Arthur packets

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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,x⟩w,ψD=⟨pi∨,x−1⟩w−1,ψA=⟨pi,C^−1(x)⟩w,ψ∨A.\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)∨=Lψ∨2(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.

References

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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