τ-CHEBYSHEV AND τ-COCHEBYSHEV SUBPSACES OF BANACH SPACES  

作　　者：H.Mazaheri 

机构地区：[1]Yazd University, Iran

出　　处：《Analysis in Theory and Applications》2006年第2期141-145,共5页分析理论与应用（英文刊）

摘　　要：The concepts of quasi-Chebyshev and weakly-Chebyshev and σ-Chebyshev were defined [3 - 7], andas a counterpart to best approximation in normed linear spaces, best coapprozimation was introduced by Franchetti and Furi^[1]. In this research, we shall define τ-Chebyshev subspaces and τ-cochebyshev subspaces of a Banach space, in which the property τ is compact or weakly-compact, respectively. A set of necessary and sufficient theorems under which a subspace is τ-Chebyshev is defined.The concepts of quasi-Chebyshev and weakly-Chebyshev and σ-Chebyshev were defined [3 - 7], andas a counterpart to best approximation in normed linear spaces, best coapprozimation was introduced by Franchetti and Furi^[1]. In this research, we shall define τ-Chebyshev subspaces and τ-cochebyshev subspaces of a Banach space, in which the property τ is compact or weakly-compact, respectively. A set of necessary and sufficient theorems under which a subspace is τ-Chebyshev is defined.

关 键 词：best approximation best coapproximation τ-Chebyshev subspace τ-cochebyshev subspace compact set weakly compact set 

分 类 号：O177.2[理学—数学]