Han's decomposition and temperedness conjectures for Langlands–Shahidi parameters

Let φ ⁣:WFLG(Q)\varphi\colon W_F\to{{}^LG}({\overline{\mathbb{Q}}_\ell}) be a semisimple LL-parameter of Langlands–Shahidi type, and let Fφ{\mathcal{F}}_\varphi be the corresponding Hecke eigensheaf. For each bB(G)b\in B(G), let GbG_b be the associated inner form, let Πφ(Gb)\Pi_\varphi(G_b) be the corresponding packet, and let i!b,reni^{b,\operatorname{ren}}_! and ib,reni^{b,\operatorname{ren}}_* denote the normalized extension functors. Han's conjectures. There is a decomposition

Fφ=bB(G),πΠφ(Gb)i!b,renπm(π),{\mathcal{F}}_\varphi=\bigoplus_{b\in B(G),\,\pi\in\Pi_\varphi(G_b)}i^{b,\operatorname{ren}}_!\pi^{\oplus m(\pi)},

where each multiplicity m(π)m(\pi) is finite and nonzero, and every summand satisfies

i!b,renπib,renπ.i^{b,\operatorname{ren}}_!\pi\cong i^{b,\operatorname{ren}}_*\pi.

These are cited in the source as Han's Conjectures 2.1.8 and 2.1.9. Their resolution is not specified in the paper.

Sources & referencesView supporting material

Primary source

Yuta Takaya and Milton Lin, “Categorification of local relative Langlands duality”, arXiv:2601.02258 (2026).

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