Articles

On the Urysohn number of a topological space

Published in: Quaestiones Mathematicae
Volume 34 , issue 4 , 2011 , pages: 441–446

DOI: 10.2989/16073606.2011.640456

Author(s): Maddalena Bonanzinga Dipartimento di Matematica, Italia , Filippo Cammaroto Dipartimento di Matematica, Italia , Mikhail Matveev* Department of Mathematical Sciences, USA

Keywords: 54A24 , 54D10 , 54A24 , 54D10

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Abstract

The Urysohn number of a space X is U(X) = min{τ: for every subset A ⊂ X such that |A| ≥ τ one can pick neighborhoods U _a ∋ a for all a ∈ A so that Some known statements about Urysohn spaces can be generalized in terms of the Urysohn number.

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