数学物理学报(英文版) ›› 2018, Vol. 38 ›› Issue (2): 643-650.doi: 10.1016/S0252-9602(18)30771-9

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A NOTE IN APPROXIMATIVE COMPACTNESS AND MIDPOINT LOCALLY K-UNIFORM ROTUNDITY IN BANACH SPACES

刘春燕, 张子厚, 周宇   

  1. School of Mathematics Physics and Statistics, Shanghai University of Engineering Science, Shanghai 201620, China
  • 收稿日期:2016-10-28 出版日期:2018-04-25 发布日期:2018-04-25
  • 通讯作者: Zihou ZHANG E-mail:zhz@sues.edu.cn
  • 作者简介:Chunyan LIU,E-mail:cyl@sues.edu.cn;Yu ZHOU,E-mail:roczhou_fly@126.com
  • 基金资助:

    Zihou Zhang is supported by the National Natural Science Foundation of China (11671252); Yu Zhou is supported by the National Natural Science Foundation of China (11771278).

A NOTE IN APPROXIMATIVE COMPACTNESS AND MIDPOINT LOCALLY K-UNIFORM ROTUNDITY IN BANACH SPACES

Chunyan LIU, Zihou ZHANG, Yu ZHOU   

  1. School of Mathematics Physics and Statistics, Shanghai University of Engineering Science, Shanghai 201620, China
  • Received:2016-10-28 Online:2018-04-25 Published:2018-04-25
  • Contact: Zihou ZHANG E-mail:zhz@sues.edu.cn
  • Supported by:

    Zihou Zhang is supported by the National Natural Science Foundation of China (11671252); Yu Zhou is supported by the National Natural Science Foundation of China (11771278).

摘要:

In this article, we prove the following results:(1) A Banach space X is weak midpoint locally k-uniformly rotund if and only if every closed ball of X is an approximatively weakly compact k-Chebyshev set; (2) A Banach space X is midpoint locally k-uniformly rotund if and only if every closed ball of X is an approximatively compact k-Chebyshev set.

关键词: k-Chebyshev set, approximatively weak compactness, approximative compactness, weak midpoint locally k-uniform rotundity, midpoint locally k-uniform rotundity, k-strict rotundity

Abstract:

In this article, we prove the following results:(1) A Banach space X is weak midpoint locally k-uniformly rotund if and only if every closed ball of X is an approximatively weakly compact k-Chebyshev set; (2) A Banach space X is midpoint locally k-uniformly rotund if and only if every closed ball of X is an approximatively compact k-Chebyshev set.

Key words: k-Chebyshev set, approximatively weak compactness, approximative compactness, weak midpoint locally k-uniform rotundity, midpoint locally k-uniform rotundity, k-strict rotundity