Metrization and semimetrization theorems with applications to manifolds

Abstract

This paper is a study of conditions under which a space with $S_2$ is metrizable, o-semimetrizable or semimetrizable. It is shown that: a $wMN$, $wgamma$-space is metrizable if and only if it has $S_2$, a quasi-$gamma$-space is metrizable if and only if it is a pseudo $wN$-space with $S_2$, a separable manifold is metrizable if and only if it has $S_2$ with property $(*)$, a perfectly normal manifold with quasi-${G}^{*}_delta$-diagonal is metrizable and a separable manifold is a hereditarily separable metrizable if and only if it has $theta$-${alpha}_2$.