Cohomology of toric origami manifolds with acyclic proper faces

TL;DR

This paper explores the cohomology of orientable toric origami manifolds with acyclic proper faces, extending previous results to more general orbit spaces and providing a comprehensive description of their equivariant cohomology rings.

Contribution

It generalizes the understanding of cohomology for toric origami manifolds by relaxing orbit space conditions and describes equivariant cohomology in broader cases.

Findings

Cohomology of toric origami manifolds with acyclic faces is characterized.

Provides a description of equivariant cohomology rings for these manifolds.

Extends previous results to non-contractible orbit spaces.

Abstract

A toric origami manifold is a generalization of a symplectic toric manifold (or a toric symplectic manifold). The origami symplectic form is allowed to degenerate in a good controllable way in contrast to the usual symplectic form. It is widely known that symplectic toric manifolds are encoded by Delzant polytopes, and the cohomology and equivariant cohomology rings of a symplectic toric manifold can be described in terms of the corresponding polytope. Recently, Holm and Pires described the cohomology of a toric origami manifold $M$ in terms of the orbit space $M/T$ when $M$ is orientable and the orbit space $M/T$ is contractible. But in general the orbit space of a toric origami manifold need not be contractible. In this paper we study the topology of orientable toric origami manifolds for the wider class of examples: we require that every proper face of the orbit space is acyclic, while the orbit space itself may be arbitrary. Furthermore, we give a general description of the equivariant cohomology ring of torus manifolds with locally standard torus actions in the case when proper faces of the orbit space are acyclic and the free part of the action is a trivial torus bundle.