3 papers
math.GN2001
Topological groups with several disconnectedness
Masasi Higasikawa
We investigate some properties of topological groups related to disconnectedness or Archimedeanness. We prove or disprove the preservation of those under operations as subgroups, q…
math.GN2001
Non-productive duality properties of topological groups
Masasi Higasikawa
We address two properties for Abelian topological groups: ``every closed subgroup is dually closed'' and ``every closed subgroup is dually embedded.'' We exhibit a pair of topologi…
math.CO2001
There is no universal countable random-free graph
Masasi Higasikawa
We consider embeddings between infinite graphs. In particular, We establish that there is no universal element in the class of countable graphs into which the random graph is not e…