Perverse character sheaf conjecture for loop Lie algebras

Let GG be a reductive group, let ξ=(M,λ,L,O,L)\xi=(M,\lambda,L,\mathcal{O},\mathcal{L}) be a polar-cuspidal datum for GG, and let QLM\mathbf{Q}\subset LM be a parahoric subgroup containing LL as a Levi factor. Let LgLgL\mathfrak{g}^{\heartsuit}\subset L\mathfrak{g} denote the regular semisimple locus, and let Sξ,Q\mathcal{S}_{\xi,\mathbf{Q}} be the associated character sheaf. Perverse character sheaf conjecture. The restriction

Sξ,QLgDLG(Lg)\mathcal{S}_{\xi,\mathbf{Q}}|_{L\mathfrak{g}^{\heartsuit}}\in D^\bullet_{LG}(L\mathfrak{g}^{\heartsuit})

is perverse in the sense of Bouthier--Kazhdan--Varshavsky. The conjecture extends the known perversity result for the affine Springer sheaf on the regular semisimple locus, while its validity for general polar-cuspidal data and parahoric subgroups remains open.

Sources & referencesView supporting material

Primary source

Ngo Bao Chau and Zhiwei Yun, “Character sheaves on loop Lie algebras: polar partition”, arXiv:2506.14584 (2025).

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