Normal Space
According to many authors (e.g., Kelley 1955, p. 112; Joshi 1983, p. 162; Willard 1970, p. 99) a normal space is a topological space in which for any two disjoint closed sets C,D there are two disjoint open sets U and V such that C subset= U and D subset= V.
Other authors (e.g., Cullen 1968, p. 118) define the notion differently, using separation axioms.
See also
Hilbert Cube, Tietze's Extension Theorem, Tychonoff Plank, Urysohn's LemmaThis entry contributed by Margherita Barile
Explore with Wolfram|Alpha
WolframAlpha
More things to try:
References
Cullen, H. F. "Normal Spaces. Completely Regular Spaces." §18 in Introduction to General Topology. Boston, MA: Heath, pp. 118-139, 1968.Joshi, K. D. Introduction to General Topology. New Delhi, India: Wiley, 1983.Kelley, J. L. General Topology. New York: Van Nostrand, 1955.Willard, S. "Normal Spaces." §15 in General Topology. Reading, MA: Addison-Wesley, pp. 99-108, 1970.Referenced on Wolfram|Alpha
Normal SpaceCite this as:
Barile, Margherita. "Normal Space." From MathWorld--A Wolfram Resource, created by Eric W. Weisstein. https://mathworld.wolfram.com/NormalSpace.html