# Stone-Čech compactification

2020 Mathematics Subject Classification: *Primary:* 54D35 [MSN][ZBL]

The largest compactification $\beta X$ of a completely-regular space $X$. Constructed by E. Čech [1] and M.H. Stone [2].

Let $\{ f_\alpha : X \rightarrow [0,1] \}_{\alpha \in A}$ be the set of all continuous functions $X \rightarrow [0,1]$. The mapping $\phi : X \rightarrow \mathbf{R}^A$, where $\phi(X)_\alpha = f_\alpha(X)$, is a homeomorphism onto its own image. Then, by definition, $\beta X = [\phi(X)]$ (where $[ \cdot ]$ denotes the operation of closure). For any compactification $b X$ there exists a continuous mapping $\beta X \rightarrow b X$ that is the identity on $X$, a fact expressed by the word "largest" .

The Stone–Čech compactification of a quasi-normal space coincides with its Wallman compactification.

#### References

[1] | E. Čech, "On bicompact spaces" Ann. of Math. , 38 (1937) pp. 823–844 |

[2] | M.H. Stone, "Applications of the theory of Boolean rings to general topology" Trans. Amer. Soc. , 41 (1937) pp. 375–481 |

[3] | R. Engelking, "Outline of general topology" , North-Holland (1968) (Translated from Polish) |

[4] | P.S. Aleksandrov, "Some results in the theory of topological spaces, obtained within the last twenty-five years" Russian Math. Surveys , 15 : 2 (1960) pp. 23–83 Uspekhi Mat. Nauk , 15 : 2 (1960) pp. 25–95 |

#### Comments

Instead of Stone–Čech compactification one finds about equally frequently Čech–Stone compactification in the literature.

#### References

[a1] | R. Engelking, "General topology" , Heldermann (1989) |

[a2] | L. Gillman, M. Jerison, "Rings of continuous functions" , Springer (1976) |

[a3] | J.R. Porter, R.G. Woods, "Extensions and absolutes of Hausdorff spaces" , Springer (1988) |

[a4] | R.C. Walker, "The Stone–Čech compactification" , Springer (1974) |

**How to Cite This Entry:**

Stone-Čech compactification.

*Encyclopedia of Mathematics.*URL: http://encyclopediaofmath.org/index.php?title=Stone-%C4%8Cech_compactification&oldid=39436