A perfectly normal locally metrizable non-paracompact space
The Polish space Y constructed in [vM1] admits no nontrivial isotopy. Yet, there exists a Polish group that acts transitively on Y.
On the set of real numbers we consider a poset (by inclusion) of topologies , where , such that iff . The poset has the minimal element , the Euclidean topology, and the maximal element , the Sorgenfrey topology. We are interested when two topologies and (especially, for ) from the poset define homeomorphic spaces and . In particular, we prove that for a closed subset of the space is homeomorphic to the Sorgenfrey line iff is countable. We study also common properties...
In this paper, a simple proof is given for the following theorem due to Blair [7], Blair-Hager [8] and Hager-Johnson [12]: A Tychonoff space is -embedded in every larger Tychonoff space if and only if is almost compact or Lindelöf. We also give a simple proof of a recent theorem of Bella-Yaschenko [6] on absolute embeddings.