Abstract
A necessary and sufficient condition is found for weak continuity of a metric projection onto a finite-dimensional subspace inl p (1<p≠2). A metric projection onto a boundedly compact set inl p is sequentially weakly upper semicontinueus. An example is given on a convex, compact set inl 2 onto which the metric projection is not weakly continuous.
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J. M. Lambert, “The weak sequential continuity of the metric projection in Lq over separable nonatomic measure spaces,” J. Approximation Theory,11, No. 4, 350–360 (1974).
V. I. Andreev, “Continuity of the metric projection in Li[S, σ, Μ]. Theory of approximation of functions,” Theses of the International Conference, Kaluga (1975), pp. 3–4.
R. B. Holmes, “On the continuity of best approximation operators,” Symposium on Infinite Dimensional Topology, Baton Rouge, 1967, Princeton Univ. Press and Univ. Tokyo Press, Princeton (1972), pp. 137–157.
B. B. Panda and O. P. Kapoor, “On equidistant sets in normed linear spaces,” Bull. Austral. Math. Soc.,11, No. 3, 443–454 (1974).
C. A. Kottman and Lin Bor-Luh, “The weak continuity of metric projection,” Michigan Math. J.,17, No. 4, 401–404 (1970).
G. Godini, “Proprietati de semicontinuitate slaba ale proiecţiei metrice cu valori mulţimi,” Stud. Cercet. Mat.,25, No. 9, 1303–1309 (1973).
V. I. Andreev, “Continuity of the metric projection in C(Q),” Metric Questions in the Theory of Functions and Mappings, No. 6, Kiev (1975), pp. 3–15.
I. Singer, Best Approximation in Normed Linear Space by Elements of a Linear Subspace, Grundlehren Math. Wiss., 171, Springer-Verlag, Berlin-New York (1970).
L. A. Lyusternik and V. I. Sobolev, Elements of Functional Analysis [in Russian], Nauka, Moscow (1965).
V. L. Klee, “Convexity of Chebyshev sets,” Math. Ann.,142, No. 3, 292–304 (1961).
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Translated from Matematicheskie Zametki, Vol. 22, No. 3, pp. 345–356, September, 1977.
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Balaganskii, V.S. Weak continuity of metric projections. Mathematical Notes of the Academy of Sciences of the USSR 22, 681–687 (1977). https://doi.org/10.1007/BF02412495
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DOI: https://doi.org/10.1007/BF02412495