Topology Atlas Document # qaaa-18 | Production Editor: Harriet Lord

© 2000 Copyright by Mikhail Matveev. All rights reserved.


Answer

Can Nice Spaces be Broken into Two Equal Parts?

Mikhail Matveev

Asked in Can Nice Spaces be Broken into Two Equal Parts? by Stephen Watson

Assume \omegan < c for all n \in \omega. For each n \in \omega, choose a subset An of the interval (1/(2n+1),1/(2n+2)) of the real line such that for \epsilon small enough, every \epsilon-neighbourhood of every point of this interval contains exactly \omegan points of An. This is easy. Now put X = {0} \cup \cup {An:n \in \omega}. It is clear that the point 0 is unique in the sense of local cardinality, so the decomposition is impossible.


Received by the editors: February 1, 2000