Separable Determination of the Fixed Point Property of Convex Sets in Banach Spaces

Separable Determination of the Fixed Point Property of Convex Sets in Banach Spaces

Year:    2016

Author:    Qingxia Li, Lili Su, Qian Wei

Journal of Mathematical Study, Vol. 49 (2016), Iss. 1 : pp. 33–41

Abstract

In this paper, we first show that for every mapping $f$ from a metric space $Ω$ to itself which is continuous off a countable subset of $Ω,$ there exists a nonempty closed separable subspace $S ⊂ Ω$ so that $f|_S$ is again a self mapping on $S.$ Therefore, both the fixed point property and the weak fixed point property of a nonempty closed convex set in a Banach space are separably determined. We then prove that every separable subspace of $c_0(\Gamma)$ (for any set $\Gamma$) is again lying in $c_0.$ Making use of these results, we finally presents a simple proof of the famous result: Every non-expansive self-mapping defined on a nonempty weakly compact convex set of $c_0(\Gamma)$ has a fixed point.

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Journal Article Details

Publisher Name:    Global Science Press

Language:    English

DOI:    https://doi.org/10.4208/jms.v49n1.16.04

Journal of Mathematical Study, Vol. 49 (2016), Iss. 1 : pp. 33–41

Published online:    2016-01

AMS Subject Headings:   

Copyright:    COPYRIGHT: © Global Science Press

Pages:    9

Keywords:    Non-expansive mapping weakly compact convex set fixed point Banach space.

Author Details

Qingxia Li

Lili Su

Qian Wei