关于Y.Yajima的一个定理

ON A THEOREM OF Y. YAJIMA

本文定义了次preortho—紧性,证明了一个空间X是次亚紧的当且仅当乘积X×βX是次preortho—紧的。这改进了Y. Yajima近来的一个定理。

In this paper we give the definition of subpreorthocompactness and prove that a space X is submetacompact if and only if the product X ×β X is subpreorthocompact which improve a theorem proved by Y. Yajima recently.