ON DELTA-NORMALITY

A subset G of a topological space is said to be a regular G(delta) if it is the intersection of the closures of a countable collection of open sets each of which contains G. A space is delta-normal if any two disjoint closed sets, of which one is a regular G(delta), can be separated by disjoint open sets. Mack has shown that a space X is countably paracompact if and only if its product with the closed unit interval is delta-normal. Nyikos has asked whether delta-normal Moore spaces need be countably paracompact. We show that they need not. We also construct a delta-normal almost Dowker space and a delta-normal Moore space having twins.