On Quasi-Chebyshevity Subsets of Unital Banach Algebras  

作　　者：M.Iranmanesh F.Soleimany 

机构地区：[1]Department of Mathematical Sciences,Shahrood University of Technology

出　　处：《Analysis in Theory and Applications》2018年第1期92-102,共11页分析理论与应用（英文刊）

摘　　要：In this paper, first, we consider closed convex and bounded subsets of infinite-dimensional unital Banach algebras and show with regard to the general conditions that these sets are not quasi-Chebyshev and pseudo-Chebyshev. Examples of those algebras are given including the algebras of continuous functions on compact sets. We also see some results in C＊-algebras and Hilbert C＊-modules. Next, by considering some conditions, we study Chebyshev of subalgebras in C＊-algebras.In this paper, first, we consider closed convex and bounded subsets of infinite-dimensional unital Banach algebras and show with regard to the general conditions that these sets are not quasi-Chebyshev and pseudo-Chebyshev. Examples of those algebras are given including the algebras of continuous functions on compact sets. We also see some results in C＊-algebras and Hilbert C＊-modules. Next, by considering some conditions, we study Chebyshev of subalgebras in C＊-algebras.

关 键 词：Best approximation Quasi-Chebyshev sets Pseudo-Chebyshev C＊-algebras HilbertC＊-modules. 

分 类 号：O177.2[理学—数学]