Separable extensions of first countable spaces
We give several topological/combinatorial conditions that, for a filter on ω, are equivalent to being a non-meager -filter. In particular, we show that a filter is countable dense homogeneous if and only if it is a non-meager -filter. Here, we identify a filter with a subspace of through characteristic functions. Along the way, we generalize to non-meager -filters a result of Miller (1984) about -points, and we employ and give a new proof of results of Marciszewski (1998). We also employ a theorem...
Let be a uniform space of uniform weight . It is shown that if every open covering, of power at most , is uniform, then is fine. Furthermore, an -metric space is fine, provided that every finite open covering is uniform.
The old game is the point-open one discovered independently by F. Galvin [7] and R. Telgársky [17]. Recall that it is played on a topological space as follows: at the -th move the first player picks a point and the second responds with choosing an open . The game stops after moves and the first player wins if . Otherwise the victory is ascribed to the second player. In this paper we introduce and study the games and . In the moves are made exactly as in the point-open game, but the...
A dense-in-itself space is called -discrete if the space of real continuous functions on with its box topology, , is a discrete space. A space is called almost--resolvable provided that is the union of a countable increasing family of subsets each of them with an empty interior. We analyze these classes of spaces by determining their relations with -resolvable and almost resolvable spaces. We prove that every almost--resolvable space is -discrete, and that these classes coincide in...