Zhou's connected-components conjecture for Hodge–Newton irreducible affine Deligne–Lusztig varieties

Let GG be an adjoint simple group, let (λ,b)(\lambda,b) be a pair consisting of a cocharacter and an element defining an affine Deligne–Lusztig variety X(λ,b)KX(\lambda,b)_K, and let ηG\eta_G be the natural map to π1(G)Γ0\pi_1(G)_{\Gamma_0}. Write π1(G)Γ0σ\pi_1(G)_{\Gamma_0}^\sigma for the set of σ\sigma-fixed points of π1(G)Γ0\pi_1(G)_{\Gamma_0}.

Zhou's conjecture. If (λ,b)(\lambda,b) is Hodge–Newton irreducible, then ηG\eta_G induces a bijection

π0(X(λ,b)K)π1(G)Γ0σ.\pi_0(X(\lambda,b)_K) \cong \pi_1(G)_{\Gamma_0}^\sigma.

This predicts that, in the Hodge–Newton irreducible case, the connected components are completely detected by the fundamental-group obstruction. The supplied text gives no resolution, so the conjecture is left open.

Sources & referencesView supporting material

Primary source

Sian Nie, “Connectedness of affine Deligne-Lusztig varieties for unramified groups”, arXiv:2107.05205 (2021).

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