Horospherical stacks

Abstract

We prove structure theorems for algebraic stacks with a reductive group action and a dense open substack isomorphic to a horospherical homogeneous space, and thereby obtain new examples of algebraic stacks which are global quotient stacks. Our results partially generalize the work of Iwanari, Fantechi, Mann and Nironi, and Geraschenko and Satriano for abstract toric stacks