Occurrence of every irreducible tensor-induction factor

Determine whether every irreducible factor of the tensor induction \(\operatorname{Ind}^{Q}_{F}\rho_\lambda\) occurs in the \(\lambda\)-isotypic component of the middle-degree completed cohomology \(\tilde{H}^{d}(K^{p})_{\overline{\mathbb{Q}}_{p}[\lambda]}\) for a strongly irreducible Galois representation \(\rho_\lambda\).

Background

The paper proves that, under strong irreducibility and a non-scalar local-inertia hypothesis, the relevant completed-cohomology eigenspace is isomorphic to a tensor induction tensored with a representation of G(Qp)\mathrm{G}(\mathbb{Q}_p). The authors explain that semisimplicity implies only that every irreducible constituent of the eigenspace is a simple factor of the tensor induction.

The unresolved issue is whether the converse holds: namely, whether all irreducible constituents of the tensor induction necessarily appear in the completed-cohomology eigenspace. The remark specifically questions whether Nekovář’s method establishes this stronger multiplicity-support assertion.

References

However it's not clear to us whether his method can show that all irreducible factors of $Ind{Q}{F}\rho\lambda$ would appear in $\tilde{H}d(Kp)_{\overline{Q_p}[\lambda]}$.

— Plectic Lie Algebra Action on Hilbert modular varieties  (2609.34465 - Jiang et al., 28 Sep 2026) in Remark immediately following Theorem 1.4 (Theorem \ref{thm-mainthm}), Section 4.1