On continuous images of Eberlein compacts
On continuous self-maps and homeomorphisms of the Golomb space
The Golomb space is the set of positive integers endowed with the topology generated by the base consisting of arithmetic progressions with coprime . We prove that the Golomb space has continuum many continuous self-maps, contains a countable disjoint family of infinite closed connected subsets, the set of prime numbers is a dense metrizable subspace of , and each homeomorphism of has the following properties: , , , and for all . Here and denotes the set of prime divisors...
On convergence spaces and groups
On countable connected Hausdorff spaces in which the intersection of every pair of connected subsets is connected.
On countable Fréchet-Urysohn spaces
On countable locally connected spaces
On countably paracompact spaces and closed maps
On covering properties by regular closed sets.
On -property of strong spaces
It is shown that every strong space is a -space. In particular, it follows that every paracompact space is a -space.
On D-connected sets in the space
On dense subspaces satisfying stronger separation axioms
We prove that it is independent of ZFC whether every Hausdorff countable space of weight less than has a dense regular subspace. Examples are given of countable Hausdorff spaces of weight which do not have dense Urysohn subspaces. We also construct an example of a countable Urysohn space, which has no dense completely Hausdorff subspace. On the other hand, we establish that every Hausdorff space of -weight less than has a dense completely Hausdorff (and hence Urysohn) subspace. We show that...
On d-paracompactness and related properties
On -compactifications and -compactifiable spaces.
On -sequentially regular spaces
On Eberlein compactifications of metrizable spaces
We prove that, for every finite-dimensional metrizable space, there exists a compactification that is Eberlein compact and preserves both the covering dimension and weight.
On embeddings into where is Lindelöf
A.V. Arkhangel’skii asked that, is it true that every space of countable tightness is homeomorphic to a subspace (to a closed subspace) of where is Lindelöf? denotes the space of all continuous real-valued functions on a space with the topology of pointwise convergence. In this note we show that the two arrows space is a counterexample for the problem by showing that every separable compact linearly ordered topological space is second countable if it is homeomorphic to a subspace of ...
On expansions of a Urysohn space to a regular space.
On extension of functors to the Kleisli category of some weakly normal monads
The problem of extension of normal functors to the Kleisli categories of the inclusion hyperspace monad and its submonads is considered. Some negative results are obtained.
On extension of the group operation over the Čech-Stone compactification
The convolution of ultrafilters of closed subsets of a normal topological group is considered as a substitute of the extension onto of the group operation. We find a subclass of ultrafilters for which this extension is well-defined and give some examples of pathologies. Next, for a given locally compact group and its dense subgroup , we construct subsets of β algebraically isomorphic to . Finally, we check whether the natural mapping from β onto β is a homomorphism with respect to the extension...
On extensions of fuzzy topologies