16 citations · 106 across the 45 of their papers we have counts for
11 papers · 1 filter
A metrizable Lawson semitopological semilattice with non-closed partial order
Taras Banakh, Serhii Bardyla, Alex Ravsky
We construct a metrizable Lawson semitopological semilattice whose partial order is not closed in . This resolves a problem posed…
Variants of the Segment Number of a Graph
Yoshio Okamoto, Alexander Ravsky, Alexander Wolff
The \emph{segment number} of a planar graph is the smallest number of line segments whose union represents a crossing-free straight-line drawing of the given graph in the plane. Th…
Closed subsets of compact-like topological spaces
Serhii Bardyla, Alex Ravsky
We investigate closed subsets (subsemigroups, resp.) of compact-like topological spaces (semigroups, resp.). We prove that each Hausdorff topological space can be embedded as a clo…
A note on compact-like semitopological groups
Alex Ravsky
The note contains a few results related to separation axioms and automatic continuity of operations in compact-like semitopological groups. In particular, is presented a semiregula…
Embeddings into countably compact Hausdorff spaces
Taras Banakh, Serhii Bardyla, Alex Ravsky
In this paper we consider the problem of characterization of topological spaces that embed into countably compact Hausdorff spaces. We study the separation axioms of subspaces of c…
Zero-sum subsets of decomposable sets in Abelian groups
Taras Banakh, Alex Ravsky
A subset of an Abelian group is if . In the paper we give partial answer to an open problem asking whether every finite decomposable s…
Positive answers to Koch's problem in special cases
Taras Banakh, Serhii Bardyla, Igor Guran +2
A topological semigroup is monothetic provided it contains a dense cyclic subsemigroup. The Koch problem asks whether every locally compact monothetic monoid is compact. This probl…
A metrizable semitopological semilattice with non-closed partial order
Taras Banakh, Serhii Bardyla, Alex Ravsky
We construct a metrizable semitopological semilattice whose partial order is a non-closed dense subset of . As a by-product we find n…
Banalytic spaces and characterization of Polish groups
Taras Banakh, Alex Ravsky
A topological space is defined to be banalytic (resp. analytic) if it is the image of a Polish space under a Borel (resp. continuous) map. A regular topological space is analytic i…
On the spread of topological groups containing subsets of the Sorgenfrey line
Taras Banakh, Igor Guran, Alex Ravsky
We prove that any topological group containing a subspace of the Sorgenfrey line has spread . Under OCA, each topological group containing an uncounta…
Computing Height-Optimal Tangles Faster
Oksana Firman, Philipp Kindermann, Alexander Ravsky +2
We study the following combinatorial problem. Given a set of y-monotone wires, a tangle determines the order of the wires on a number of horizontal layers such that the orders…