Abreu–Nigro's homeomorphism conjecture for regular semisimple Lusztig varieties

Let G=GLn(C)G=\operatorname{GL}_n(\mathbb{C}), let sGrs\mathbf{s}\in G^{\mathrm{rs}} be regular semisimple, and let w,wSnw,w'\in S_n be smooth permutations associated, via the natural combinatorial map from smooth permutations to linear Hessenberg subspaces, to the same linear Hessenberg space HH. Thus ww is the unique codominant permutation with

XH(s)=Yw(s),X_H(s)=Y_w(\mathbf{s}),

and the varieties Yw(s)Y_w(\mathbf{s}) and Yw(s)Y_{w'}(\mathbf{s}) have isomorphic graded SnS_n-representations in cohomology. Abreu–Nigro's homeomorphism conjecture. The regular semisimple Lusztig varieties Yw(s)Y_w(\mathbf{s}) and Yw(s)Y_{w'}(\mathbf{s}) are homeomorphic. This would strengthen the known equality of their GKM graphs and graded SnS_n-representations by identifying the varieties topologically; the source gives no resolution of the conjecture.

Sources & referencesView supporting material

Primary source

Patrick Brosnan, Jaehyun Hong and Donggun Lee, “Geometry of regular semisimple Lusztig varieties”, arXiv:2504.15868 (2026).

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