The regular open-open topology for function spaces.
Hewitt [Rings of real-valued continuous functions. I., Trans. Amer. Math. Soc. 64 (1948), 45–99] defined the -topology on , denoted , and demonstrated that certain topological properties of could be characterized by certain topological properties of . For example, he showed that is pseudocompact if and only if is a metrizable space; in this case the -topology is precisely the topology of uniform convergence. What is interesting with regards to the -topology is that it is possible, with...
A space is said to have the Rothberger property (or simply is Rothberger) if for every sequence of open covers of , there exists for each such that . For any , necessary and sufficient conditions are obtained for to have the Rothberger property when is a Mrówka mad family and, assuming CH (the Continuum Hypothesis), we prove the existence of a maximal almost disjoint family for which the space is Rothberger for all .
Let X be an atom (= hereditarily indecomposable continuum). Define a metric ϱ on X by letting where is the (unique) minimal subcontinuum of X which contains x and y and W is a Whitney map on the set of subcontinua of X with W(X) = 1. We prove that ϱ is an ultrametric and the topology of (X,ϱ) is stronger than the original topology of X. The ϱ-closed balls C(x,r) = y ∈ X:ϱ ( x,y) ≤ r coincide with the subcontinua of X. (C(x,r) is the unique subcontinuum of X which contains x and has Whitney value...
We establish the topological relationship between compact Hausdorff spaces X and Y equivalent to the existence of a bound-2 isomorphism of the sup norm Banach spaces C(X) and C(Y).
Let be the space of all lower semi-continuous extended real-valued functions on a Hausdorff space , where, by identifying each with the epi-graph , is regarded the subspace of the space of all closed sets in with the Fell topology. Let We show that is homeomorphic to the Hilbert cube if and only if is second countable, locally compact and infinite. In this case, it is proved that is homeomorphic to (resp. ) if is compact (resp. is non-compact), where is the cone over...