A new method for constructing a compact and non SI-compact space

Abstract

In this paper, we provide a new method for constructing a compact and non SI-compact space and thus give a new answer for the question posed by Zhao and Ho. Using this method, we find a countable compact space which fails to be SI-compact. As a corollary, some new non sober frames are obtained and thus we give a new answer for a question raised by A.Jung. Inspired by the definition of SI-compactness, we introduce a new notion of compactness of topological spaces, namely, v-compactness, which is stronger than SI-compactness.Some properties of v-compactness, SI-compactness and weak v-compactness are discussed. Specifically, we prove that (1) all closed subspaces of a v-compact(SI-compact,weakly v-compact) space are v-compact (SI-compact, weakly v-compact);(2) a characterization of v-compactness for the upper topology is given; (3)some characterizations of weakly v-compact subsets of real line and Sorgenfrey line are given.