Published online by Cambridge University Press: 20 November 2018
Suppose x = (x∝) is a net with values in a metric space X having metric ρ. If a point z in X can be found to minimize
then z is called a center point (c.p.) of x. The space X is (netwise) c.p. complete if every bounded net has at least one c.p.; it is sequentially c.p. complete if every bounded sequence has a c.p. Netwise c.p. completeness implies sequential c.p. completeness, and the latter implies completeness since any c.p. of a Cauchy sequence will necessarily be a limit point of that sequence.
These notions are related to the set centers of Calder et al. [2].