C(R)中非线性最佳逼近的特征

Best Characterizations of Nonlinear Approximation in C(R)

对 C(R)中一类非凸子集,在一特定的距离下,给出了最佳逼近的特征,其中包括 Kolmogorov 型与 Chebyshev 交错型特征定理。作为推论,我们得到了在这距离下有理最佳逼近的特征.

Give best characterizations of nonlinear approximation of a family of subsets not only convex in the space C(R) enowed with a certain metric,which include the characterizations of“Kolmogorov”type and“Chebyshev alternation”type.As the corollaries,we obtain the characterizations of rational best approximation in the metric too.