1978/12/31 by А. В. Архангельский · 212 citations
Computer Science · Decision Sciences · Mathematics · #Advanced Algebra and Logic #Combinatorics #Fuzzy and Soft Set Theory #Mathematics #Pure mathematics #Rings, Modules, and Algebras #Topological space #Topology (electrical circuits)
paper · pdf · doi:10.1070/rm1978v033n06abeh003884
published in Russian Mathematical Surveys 33(6), 33-96 (IOP Publishing)
openalex publication_date 1978/12/31 · openalex created_date 2025/10/10 · openalex updated_date 2025/11/06
In this paper we introduce and study three new cardinal topological invariants called the cs * -, cs-, and sb-characters. The class of topological spaces with countable cs * -character is closed under many topological operations and contains all -spaces and all spaces with point-countable cs * -network. Our principal result states that each non-metrizable sequential topological group with countable cs *character has countable pseudo-character and contains an open ksubgroup. This result is specific for topological groups: under Martin Axiom there exists a sequential topologically homogeneous k-space X with 0 = cs * (X) < (X).