Quasi-convex subsets and the farthest direction in Alexandrov spaces with lower curvature bound.

This paper aims to give a further study on quasi-convex subsets in Alexandrov spaces with lower curvature bound which are introduced in [SSW]. We first provide new insights on quasi-convex subsets (Theorem A and Corollary C), and then as applications of them we explore more properties of quasi-convex subsets.