Blockers in hyperspaces

Abstract: Given a metric continuum X, let and denote the hyperspaces of all nonempty closed subsets and subcontinua, respectively. For we say that B does not block A if and the union of all subcontinua of X intersecting A and contained in is dense in X. In this paper we study some sets of blockers for several kinds of continua. In particular, we determine their Borel classes and, for a large class of locally connected continua X, we recognize them as cap-sets. [Copyright &y& Elsevier]