The character identity conjecture for disconnected groups

From papers

Let ϕ:LFLG\phi:L_F\to{}^LG be a tempered Langlands parameter, let s~S~ϕ[z]\tilde s\in\tilde S_\phi^{[z]} be semisimple, and let e\mathfrak e be the associated endoscopic datum. Choose a zz-pair and write ϕz\phi^{\mathfrak z} for the induced parameter. Let Π~ϕ,z\tilde\Pi_{\phi,z} be parametrized by Irr(π0(S~ϕ[z]),[z])\operatorname{Irr}(\pi_0(\tilde S_\phi^{[z]}),[z]), with ρ~π~ρ~\tilde\rho\mapsto\tilde\pi_{\tilde\rho}. The character identity conjecture. For matching functions ff and fzf^{\mathfrak z}, one has

SΘϕz(fz)=ρ~tr(ρ~)(s~)Θπ~ρ~(f),S\Theta_{\phi^{\mathfrak z}}(f^{\mathfrak z})=\sum_{\tilde\rho}\operatorname{tr}(\tilde\rho)(\tilde s)\,\Theta_{\tilde\pi_{\tilde\rho}}(f),

where the sum runs over Irr(π0(S~ϕ[z]),[z])\operatorname{Irr}(\pi_0(\tilde S_\phi^{[z]}),[z]). This is the expected endoscopic character relation accompanying the local Langlands parametrization; its validity depends on the conjectural packets and transfer factors for disconnected groups.

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Sources & referencesView supporting material

Primary source

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

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