Toric Constructions via Integral Transversality

Abstract

In the Delzant world, symplectic toric manifolds correspond to unimodular polytopes, and unimodularity-preserving polytope constructions correspond to geometric constructions on the manifold side. We treat, in a unified framework, constructions such as taking a face, taking a slice, and polytope intersections, identifying each with its geometric counterpart, namely invariant submanifolds, symplectic reduction, and reduction of a product (a full list appears in Table 1). The key tool is "integral transversality", a lattice-refined transversality condition that provides a uniform criterion for preserving unimodularity, ensuring smoothness on the manifold side. To keep every construction within a single ambient vector space -- the dual of the Lie algebra of a fixed torus -- we allow the torus actions involved to have nontrivial, but connected kernels.