Characters of countably tight spaces and inaccessible cardinals

Research output: Contribution to journalArticle

Abstract

In this paper, we study some connections between characters of countably tight spaces of size ω1 and inaccessible cardinals. A countable tight space is indestructible if every σ-closed forcing notion preserves countable tightness of the space. We show that, assuming the existence of an inaccessible cardinal, the following statements are consistent:(1)Every indestructibly countably tight space of size ω1 has character ≤ω1.(2)2ω12 and there is no countably tight space of size ω1 and character ω2. For the converse, we show that, if ω2 is not inaccessible in the constructible universe L, then there is an indestructibly countably tight space of size ω1 and character ω2.

Original languageEnglish
Pages (from-to)95-106
Number of pages12
JournalTopology and its Applications
Volume161
Issue number1
DOIs
Publication statusPublished - 2014
Externally publishedYes

Fingerprint

Countable Tightness
Constructible
Converse
Forcing
Countable
Character
Closed

Keywords

  • Countable tight space
  • Countable tightness indestructibility
  • Inaccessible cardinal
  • Kurepa tree
  • Primary
  • Topological game

ASJC Scopus subject areas

  • Geometry and Topology

Cite this

Characters of countably tight spaces and inaccessible cardinals. / Usuba, Toshimichi.

In: Topology and its Applications, Vol. 161, No. 1, 2014, p. 95-106.

Research output: Contribution to journalArticle

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