$π$-metrizable spaces and strongly $π$-metrizable spaces

Fucai Lin, Shou Lin

Published 2013-02-18Version 1

A space $X$ is said to be $\pi$-metrizable if it has a $\sigma$-discrete $\pi$-base. In this paper, we mainly give affirmative answers for two questions about $\pi$-metrizable spaces. The main results are that: (1) A space $X$ is $\pi$-metrizable if and only if $X$ has a $\sigma$-hereditarily closure-preserving $\pi$-base; (2) $X$ is $\pi$-metrizable if and only if $X$ is almost $\sigma$-paracompact and locally $\pi$-metrizable; (3) Open and closed maps preserve $\pi$-metrizability; (4) $\pi$-metrizability satisfies hereditarily closure-preserving regular closed sum theorems. Moreover, we define the notions of second-countable $\pi$-metrizable and strongly $\pi$-metrizable spaces, and study some related questions. Some questions about strongly $\pi$-metrizability are posed.