Larsen's Galois maximality conjecture for compatible systems

From papers

Let KK be a finitely generated field, let XX be a smooth projective variety over KK, and consider a \mathdsQ\mathds{Q}-compatible system of Galois representations

{ρ ⁣:GKGL(Heˊti(XK,\mathdsQ))}.\{\rho_{\ell} \colon G_K \to \operatorname{GL}(\operatorname{H}^{i}_{\operatorname{\acute{e}t}}(X_{\overline{K}},\mathds{Q}_{\ell}))\}.

Let Gsc\mathbf{G}_{\ell}^{\operatorname{sc}} be the simply connected cover of the adjoint algebraic monodromy group, and let Γsc\Gamma_{\ell}^{\operatorname{sc}} be the inverse image of the adjoint Galois image in Gsc(\mathdsQ)\mathbf{G}_{\ell}^{\operatorname{sc}}(\mathds{Q}_{\ell}). Larsen's Galois maximality conjecture. For all sufficiently large primes \ell, Γsc\Gamma_{\ell}^{\operatorname{sc}} is a maximal compact subgroup of Gsc(\mathdsQ)\mathbf{G}_{\ell}^{\operatorname{sc}}(\mathds{Q}_{\ell}). Moreover, it is hyperspecial: there exists a smooth affine group scheme Gsc\mathscr{G}_{\ell}^{\operatorname{sc}} over \mathdsZ\mathds{Z}_{\ell} such that

Gsc(\mathdsZ)=Γsc.\mathscr{G}_{\ell}^{\operatorname{sc}}(\mathds{Z}_{\ell})=\Gamma_{\ell}^{\operatorname{sc}}.

This is presented as a weaker form of the Galois maximality conjecture for arbitrary smooth projective varieties. The supplied text gives no resolution status for this assertion.

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Sources & referencesView supporting material

Primary source

Zhichao Tang and Haitao Zou, “Monodromy rank and the semisimple Mumford-Tate conjecture for hyper-Kähler varieties”, arXiv:2602.19835 (2026).

Additional references

2 papers in this index state this conjecture (2017–2026). The statement above is taken from the most recent of them; the others are arXiv:1707.07366.

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