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nLab countably compact topological space (Rev #4)

Context

Analysis

Topology

topology (point-set topology, point-free topology)

see also differential topology, algebraic topology, functional analysis and topological homotopy theory

Introduction

Basic concepts

Universal constructions

Extra stuff, structure, properties

Examples

Basic statements

Theorems

Analysis Theorems

topological homotopy theory

Contents

Definition

A topological space is called countably compact if every open cover consisting of a countable set of open subsets (every countable cover) admits a finite subcover, hence if there is a finite subset of the open in the original cover which still cover the space.

Examples

For the case of metric spaces, countably compact metric spaces are equivalently compact metric spaces.

  • The long line is an example of a countably compact space that is not compact.

Revision on July 25, 2018 at 20:41:54 by Todd Trimble See the history of this page for a list of all contributions to it.