Proceedings of the American Mathematical Society

Published by the American Mathematical Society since 1950, Proceedings of the American Mathematical Society is devoted to shorter research articles in all areas of pure and applied mathematics.

ISSN 1088-6826 (online) ISSN 0002-9939 (print)

The 2024 MCQ for Proceedings of the American Mathematical Society is 0.85.

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A note on the stability of nonsurjective $\varepsilon$-isometries of Banach spaces
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by Lixin Cheng and Yunbai Dong
Proc. Amer. Math. Soc. 148 (2020), 4837-4844
DOI: https://doi.org/10.1090/proc/15110
Published electronically: July 30, 2020

Abstract:

Let $X, Y$ be Banach spaces, and let $f: X\rightarrow Y$ be an $\varepsilon$-isometry with $f(0)=0$ for some $\varepsilon \geq 0$. In this paper, we show that for every $x^*\in X^*$, there exists $\varphi \in Y^*$ with $\|\varphi \|=\|x^*\|\equiv r$ such that \begin{equation} \big |\langle x^*,x\rangle -\langle \varphi ,f(x)\rangle \big |\leq 3r\varepsilon ,\;\;\forall \;x\in X.\nonumber \end{equation} Moreover, the constant “3” is the best one in general.
References
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Bibliographic Information
  • Lixin Cheng
  • Affiliation: School of Mathematical Sciences, Xiamen University, Xiamen, 361005, People’s Republic of China
  • Email: lxcheng@xmu.edu.cn
  • Yunbai Dong
  • Affiliation: Research Center of Nonlinear Science and School of Mathematics and Computer, Wuhan Textile University, Wuhan, 430073, People’s Republic of China
  • Email: baiyunmu301@126.com
  • Received by editor(s): February 7, 2020
  • Received by editor(s) in revised form: March 17, 2020, and March 24, 2020
  • Published electronically: July 30, 2020
  • Additional Notes: The first author was supported by NSFC, grant 11731010.
    The second author is the corresponding author
    The second author was supported by NSFC, grant 11671314.
  • Communicated by: Stephen Dilworth
  • © Copyright 2020 American Mathematical Society
  • Journal: Proc. Amer. Math. Soc. 148 (2020), 4837-4844
  • MSC (2010): Primary 46B04; Secondary 46B20, 47A58
  • DOI: https://doi.org/10.1090/proc/15110
  • MathSciNet review: 4143398