A note on the convexity of Chebyshev sets - doi: 10.5269/bspm.v27i1.9068
DOI:
https://doi.org/10.5269/bspm.v27i1.9068Palavras-chave:
Convex set, Cheybshev set, Convex space, Strongly convex space, Metric projection, Non-expansive mapResumo
Perhaps one of the major unsolved problem in Approximation Theory is : Whether or not every Chebyshev subset of a Hilbert space must be convex. Many partial answers to this problem are available in the literature. R.R. Phelps [Proc. Amer. Math. Soc. 8 (1957), 790-797] showed that a Chebyshev set in an inner product space (or in a strictly convex normed linear space) is convex if the associated metric projection is non-expansive. We extend this result to metric spaces.Downloads
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2009-12-17
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