Preservation of approximative properties of subsets

A. R. Alimov

Izvestiya. Mathematics , Tome 70 (2006) no. 5, pp. 857-866.

Résumé

We describe the subsets $\Pi\subset\mathbb R^n$ whose intersection with a Chebyshev set (sun, or strict sun) $M$ in $\ell^\infty(n)$ preserves the approximative properties of $M$ in $\ell^\infty(n)$.

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