Cotangent-case Borel-orbit duality conjecture

Let GG be a reductive group with Langlands dual group GG^\vee, and let WW be the Weyl group. Let XX be a smooth spherical GG-variety such that TXT^*X is hyperspherical and has relative Langlands dual of the form TXT^*X^\vee for a smooth spherical GG^\vee-variety XX^\vee. Let B\XB\backslash X and B\XB^\vee\backslash X^\vee denote the sets of Borel orbits, and let rank(Y)\operatorname{rank}(Y) denote the dimension of the lattice of BB-semi-invariant rational-function characters on a variety YY. Cotangent-case orbit-duality conjecture. There exists a bijection

Φ:B\XB\X\Phi:B\backslash X\longrightarrow B^\vee\backslash X^\vee

that intertwines Knop's Weyl-group action and satisfies rank(x)+rank(Φ(x))=rank(G)\operatorname{rank}(x)+\operatorname{rank}(\Phi(x))=\operatorname{rank}(G). For every simple reflection sWs\in W, an orbit xB\Xx\in B\backslash X has type GG with respect to ss if and only if Φ(x)\Phi(x) has type T2T2 with respect to ss, and conversely.

This conjecture translates the relative Langlands duality prediction into combinatorics of Borel orbits. The source proposes it based on computations used in proving the main theorem; no resolution is given.

Sources & referencesView supporting material

Primary source

Guy Kapon and Guy Shtotland, “On Representations of Weyl Groups attached to Spherical Varieties”, arXiv:2607.24108 (2026).

Progress summary

Never refreshed

Nothing recorded yet. Refresh searches the literature and the public web for attempts on this problem, and writes the first summary here.

Solutions 0

No solutions have been posted yet.