Scheme-theoretic traditional Humphreys conjecture

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Assume p>hp>h. Let Wext∅W_{\mathrm{ext}}^\varnothing be the set of minimal coset representatives, let T(λ)\mathsf T(\lambda) be the indecomposable tilting module, let N\mathcal N be the nilpotent cone, and let C‾\overline C be the reduced closed subscheme associated with the orbit closure of the orbit corresponding to the two-sided cell containing ww.

Scheme-theoretic traditional Humphreys conjecture. For every w∈Wext∅w\in W_{\mathrm{ext}}^\varnothing, the coherent sheaf

Ext⁡Rep(G1)∙(T(w∙0),T(w∙0))\operatorname{Ext}^\bullet_{\mathsf{Rep}(\mathbf G_1)}(\mathsf T(w\bullet0),\mathsf T(w\bullet0))

is scheme-theoretically supported on C‾\overline C.

This is described as a priori stronger than the set-theoretic traditional Humphreys conjecture. The supplied text does not state whether it has been resolved.

References

Primary source

Pramod N. Achar and Simon Riche, “Tilting modules for reductive algebraic groups: characters and support varieties”, arXiv:2511.05063 (2025).

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