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Relations approximated by continuous functions
Authors:L'. Holá     R. A. McCoy
Affiliation:Mathematical Institute, Slovak Academy of Sciences, Stefánikova 49, 814 73 Bratislava, Slovakia ; Department of Mathematics, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061
Abstract:Let $X$ be a Tychonoff space, let $C(X)$ be the space of all continuous real-valued functions defined on $X$ and let $CL(X times R)$ be the hyperspace of all nonempty closed subsets of $Xtimes R$. We prove the following result. Let $X$ be a locally connected, countably paracompact, normal $q$-space without isolated points, and let $F in CL(X times R)$. Then $F$ is in the closure of $C(X)$ in $CL(X times R)$ with the locally finite topology if and only if $F$is the graph of a cusco map. Some results concerning an approximation in the Vietoris topology are also given.

Keywords:Set-valued mapping   Vietoris topology   locally finite topology   upper-semicontinuous multifunction   usco map   cusco map
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