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A theorem of Nepomnyashchii on continuous subset-selections - MaRDI portal

A theorem of Nepomnyashchii on continuous subset-selections (Q1888472)

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scientific article; zbMATH DE number 2117956
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A theorem of Nepomnyashchii on continuous subset-selections
scientific article; zbMATH DE number 2117956

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    A theorem of Nepomnyashchii on continuous subset-selections (English)
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    23 November 2004
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    Let \(X\) be a paracompact space, \(Y\) a completely metrizable one, and \(F: X\to Y\) a lower-semicontinuous multifunction with closed and equi-\(\text{LC}^0\) values. Let \(G: X\to Y\) be any upper-semicontinuous relation with compact (possibly empty) values such that \(G(x)\subset F(x)\), \(x\in X\). The following sandwich theorem is proved: if every \(F(x)\) is connected then there exists a continuous multifunction \(H: X\to Y\) with compact and connected values such that \(G(x)\subset H(x)\subset F(x)\), \(x\in X\). When \(G(x)= \emptyset\), \(x\in X\) this reduces to a multiselection theorem of Nepomnyashchii, although the proof is different. Four examples illustrating the essentiality of the assumptions are provided.
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    multifunction
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    multiselection
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    equi-\(\text{LC}^0\)
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    sandwich theorem
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