Abstract:In this paper we improve some mapping theorems on $\aleph $-spaces. For instance we show that an $\aleph $-space is preserved by a closed and countably bi-quotient map. This is an improvement of Yun Ziqiu's theorem: an $\aleph $-space is preserved by a closed and open map.
Keywords: $\aleph $-space, $k$-network, closed map, countably bi-quotient map
AMS Subject Classification: 54C10, 54E18