Regular-quotient gluing conjecture for spherical varieties

Let X=G/HX=G/H be an affine homogeneous spherical variety with abelian regular centralizers and no type NN roots. Let c=(h)/ ⁣/H\mathfrak c=(\mathfrak h^\perp){/\!/}H, let (h)reg\fatslashH(\mathfrak h^\perp)^\mathrm{reg}\mathbin{\mkern-6mu\fatslash}H be the regular quotient, and let Dnsc\mathfrak D_{ns}\subset\mathfrak c be a divisor. Regular-quotient gluing conjecture. Away from a codimension 22 locus in c\mathfrak c, there is an identification

(h)reg\fatslashHccDnsc.(\mathfrak h^\perp)^\mathrm{reg}\mathbin{\mkern-6mu\fatslash}H\simeq \mathfrak c\coprod_{\mathfrak c\setminus\mathfrak D_{ns}}\mathfrak c.

Thus the regular quotient is expected to be obtained by gluing two copies of the GIT quotient along the complement of a divisor. The paper says that this is verified in several examples, but does not establish it in general.

Sources & referencesView supporting material

Primary source

Thomas Hameister, Zhilin Luo and Benedict Morrissey, “Relative Dolbeault Geometric Langlands via the Regular Quotient”, arXiv:2409.15691 (2025).

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