THE 2-KKM PRINCIPLE IN ABSTRACT CONVEX SPACES :EQUIVALENT FORMULATIONS AND APPLICATIONS

摘要

Since any family of closed balls in a hyperconvex metric space hasnonempty intersection whenever each two members of the family intersects. Mo-tivated by this fact, T.-1I. Chang et al. [2-4] introduced 2-KKM maps for hyper-convex metric spaces. In this paper, we seek equivalents or consequences of the2-KKM theorem when it is available.