Equivariant Quantisation of Hypertoric Varieties via Symplectic Cuts

We study the equivariant geometric quantisation of a non-compact hypertoric orbifold of complex dimension $2n$ by compact symplectic cuts. When the defining arrangement has a non-empty bounded base region and the fixed lift is integral, we prove that, at every positive regular integral level $d$, the space of sections on the cut is the sum of the fibre-rotation weight spaces of weight at most $d$ in the original quantisation. The higher cohomology of the cut pre-quantum line orbibundle vanishes, so its equivariant index is the character of its actual section space. Using the moment polyptychs introduced in a companion paper, we give an orbifold Kawasaki-Riemann-Roch localisation formula for this character. We also compute it as a weighted lattice-point sum: a residual weight $x$ occurs at level $d$ if and only if the arrangement slack function satisfies $\mathcal{S}(x) \leq d$, with multiplicity $\binom{d - \mathcal{S}(x) + n}{n}$. The examples compare these calculations in rank one, including a cut with an orbifold point, and in rank two, for smooth cuts that are not toric.

Authors

Publication Details

Journal
arXiv (Cornell University)
Published
2026-11-10
DOI
https://doi.org/10.48550/arxiv.2611.14090
Primary Topic
Algebraic Geometry and Number Theory
Type
preprint
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preprint

Equivariant Quantisation of Hypertoric Varieties via Symplectic Cuts

Benjamin C. W. Brown
arXiv (Cornell University)
Algebraic Geometry and Number Theory
preprint

Equivariant Quantisation of Hypertoric Varieties via Symplectic Cuts

Benjamin C. W. Brown
preprint en

Abstract

We study the equivariant geometric quantisation of a non-compact hypertoric orbifold of complex dimension $2n$ by compact symplectic cuts. When the defining arrangement has a non-empty bounded base region and the fixed lift is integral, we prove that, at every positive regular integral level $d$, the space of sections on the cut is the sum of the fibre-rotation weight spaces of weight at most $d$ in the original quantisation. The higher cohomology of the cut pre-quantum line orbibundle vanishes, so its equivariant index is the character of its actual section space. Using the moment polyptychs introduced in a companion paper, we give an orbifold Kawasaki-Riemann-Roch localisation formula for this character. We also compute it as a weighted lattice-point sum: a residual weight $x$ occurs at level $d$ if and only if the arrangement slack function satisfies $\mathcal{S}(x) \leq d$, with multiplicity $\binom{d - \mathcal{S}(x) + n}{n}$. The examples compare these calculations in rank one, including a cut with an orbifold point, and in rank two, for smooth cuts that are not toric.

arXiv (Cornell University)
Algebraic Geometry and Number Theory
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