Quasimaps and some examples of stacks for everybody

Abstract

This note introduces the theory of quasimaps to GIT quotients with intuition and concrete examples, with the goal of explaining a closed formula for the quasimap $I$-function. Along the way, it emphasizes aspects of this story that illustrate general stacky concepts.

Final version. To appear in the volume "Singularities, Mirror Symmetry, and the Gauged Linear Sigma Model."