Canonical splitting and unramifiedness compatibility conjecture

Let K\mathcal{K} be the set of relevant subgroups, let HφH_\varphi be the image defined in the preceding diagrams, and let \phi_\overline{\overline{\overline{\overline{\chi}}}} be the parameter of an unramified genuine character. Let \mathcal{S}(\phi_\overline{\overline{\overline{\overline{\chi}}}}) be its component group. Unramified packet compatibility conjecture. There is a canonical splitting sφs_\varphi of ΓGQ,ntor^\widehat{\Gamma_{G_{Q,n}}^{\rm tor}} over ΓGQ,ntor^/Hφ\widehat{\Gamma_{G_{Q,n}}^{\rm tor}}/H_\varphi, together with a bijection

\mathcal{L}(\phi_\overline{\overline{\overline{\overline{\chi}}}})\longleftrightarrow\operatorname{Irr}(\mathcal{S}(\phi_\overline{\overline{\overline{\overline{\chi}}}})),

written \pi(\phi_\overline{\overline{\overline{\overline{\chi}}}},\rho)\leftrightarrow\rho. For every KKK\in\mathcal{K}, splitting sK:KGs_K:K\hookrightarrow\overline{G} agreeing with sQ,ns_{Q,n} on T(O)\mathbf{T}(O), fzHom(K,μn)f_z\in\operatorname{Hom}(K,\mu_n)^\natural, and yΓGtor^y\in\widehat{\Gamma_G^{\rm tor}} such that ysKy\cdot s_K is associated with sKs_K, one has that \pi(\phi_\overline{\overline{\overline{\overline{\chi}}}},\rho) is (K,sK)(K,s_K)-unramified if and only if \pi(\phi_\overline{\overline{\overline{\overline{\chi}}}},\gamma_{z,y}\cdot\rho) is (yK,(yfz)(ysK))(y\cdot K,(y\cdot f_z)\otimes(y\cdot s_K))-unramified, where

γz,y=(φhiK(fz))(sφφ(y)).\gamma_{z,y}=\bigl(\varphi\circ h\circ i_K^\natural(f_z)\bigr)\cdot\bigl(s_\varphi\circ\varphi(y)\bigr).

This would describe how unramifiedness transforms under the dual torus and character actions.

Sources & referencesView supporting material

Primary source

Fan Gao, Freydoon Shahidi and Dani Szpruch, “Restrictions, L-parameters, and local coefficients for genuine representations”, arXiv:2102.08859 (2021).

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