Subdivision conjecture for moment polyhedra of Kac–Moody flag varieties

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Let GG be a Kac–Moody group of finite rank, and let cc be a Coxeter element. Write ΦT(G/B)\Phi_T(G/B) for the moment polyhedron of the Kac–Moody flag ind-scheme G/BG/B, and let XwwcX_w^{wc} denote the corresponding Richardson variety whenever wcwc is length-additive.

Subdivision conjecture. The moment polyhedron ΦT(G/B)\Phi_T(G/B) has a locally finite subdivision into Bruhat interval polytopes

{ΦT(Xwwc):wc length-additive}.\{\Phi_T(X_w^{wc}): wc\text{ length-additive}\}.

This proposes a Kac–Moody analogue of the finite-type subdivision results for permutahedra and Lusztig varieties. Since the source presents it as a conjectural statement and supplies no resolution evidence, its status is open.

References

Primary source

Allen Knutson, Mario Sanchez and Melissa Sherman-Bennett, “Permutahedra, Lusztig varieties, degenerations, and subdivisions”, arXiv:2607.02701 (2026).

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