"Borel complexity of ideal limit points"
He, XiThis is joint work with Hang Zhang (Southwest Jiaotong University) and Shuguo Zhang (Sichuan University). The (set of) ideal limit points is defined by replacing ''finite sets'' with ''sets of an ideal'' in the definition of the ordinary limit points. Generally speaking, ideal limit points is not necessarily closed, and its complexity is not easy to calculate. We will introduce the related research of ideal limit points, focusing on whether it is Borel and some properties of low complexity (closed or $F_\sigma$), and point out the relationship between these studies and some combinatorial properties.