Pavel Samuilovich Urysohn was a Soviet mathematician, born on 3 February 1898 and died on 17 August 1924, best known for his contributions to the theory of topological dimension and for developing Urysohn's metrization theorem and Urysohn's lemma, both fundamental results in topology. He also constructed what is now called the Urysohn universal space. His name is commemorated in the terms Frechet-Urysohn space, Menger-Urysohn dimension and Urysohn integral equation, and with Pavel Alexandrov he formulated the modern definition of compactness in 1923.
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1. Pavel Urysohn (Wikipedia)
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his contributions to the theory of topological dimension, and fo
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was a Soviet mathematician
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fundamental results in topology
View the SourceUrysohn's Lemma (Wikipedia)
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In topology, Urysohn's lemma is a lemma that states that a topological space is normal if and only if any two disjoint closed subsets can be
Tietze Extension Theorem (Wikipedia)
Wikimedia FoundationProofs Credited: Tietze Extension Theorem, Lead paragraphQuote, Proofs Credited: Tietze Extension Theorem, Lead paragraph
In topology, the Tietze extension theorem (also known as the Tietze-Urysohn-Brouwer extension theorem or Urysohn-Brouwer lemma) states that any real-valued, continuous function on a closed subset
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