Some properties of uniform ordered spaces
A rotoid is a space X with a special point e ∈ X and a homeomorphism F: X² → X² having F(x,x) = (x,e) and F(e,x) = (e,x) for every x ∈ X. If any point of X can be used as the point e, then X is called a strong rotoid. We study some general properties of rotoids and prove that the Sorgenfrey line is a strong rotoid, thereby answering several questions posed by A. V. Arhangel'skii, and we pose further questions.
A space is truly weakly pseudocompact if is either weakly pseudocompact or Lindelöf locally compact. We prove: (1) every locally weakly pseudocompact space is truly weakly pseudocompact if it is either a generalized linearly ordered space, or a proto-metrizable zero-dimensional space with for every ; (2) every locally bounded space is truly weakly pseudocompact; (3) for , the -Lindelöfication of a discrete space of cardinality is weakly pseudocompact if .
We show that if is first-countable, of countable extent, and a subspace of some ordinal, then is Lindelöf.
We investigate spaces over LOTS (linearly ordered topological spaces). We find natural necessary conditions for linear Lindelöfness of over LOTS. We also characterize countably compact LOTS whose is linearly Lindelöf for each n. Both the necessary conditions and the characterization are given in terms of the topology of the Dedekind completion of a LOTS.
In quest'articolo dimostriamo come il concetto «spezzabilità», formulato e sviluppato di Arhangel'skii, viene trasferito dallo studio di spazi topologici a quello di spazi topologici parzialmente ordinati. Otteniamo numerosi risultati in forma «se è spezzabile (facendo uso di funzioni appropriatamente scelte) su spazi che hanno una proprietà, allora anche soddisfa la stessa proprietà».
We examine the Gruenhage property, property * (introduced by Orihuela, Smith, and Troyanski), fragmentability, and the existence of σ-isolated networks in the context of linearly ordered topological spaces (LOTS), generalized ordered spaces (GO-spaces), and monotonically normal spaces. We show that any monotonically normal space with property * or with a σ-isolated network must be hereditarily paracompact, so that property * and the Gruenhage property are equivalent in monotonically normal spaces....