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New York Journal of Mathematics
Volume 30 (2024), 1196-1219

  

Qiang Tu, Xiaohuan Mu, and Tiexin Guo

The random Markov-Kakutani fixed point theorem in a random locally convex module

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Published: August 20, 2024.
Keywords: Random locally convex modules, stable compactness, random Markov-Kakutani fixed point theorem, random Hahn-Banach theorem.
Subject [2010]: 46H25, 41A50, 47H10, 46A22.

Abstract
Based on the recently developed theory of σ-stable sets and stable compactness, we first establish the random Markov-Kakutani fixed point theorem in a random locally convex module: let (E,P) be a random locally convex module and G be a nonempty stably compact L0-convex subset of E, then every commutative family of Tc(Pcc)-continuous L0-affine mappings from G to G has a common fixed point, where Pcc is the σ-stable hull of P and Tc(Pcc) is the locally L0-convex topology induced by Pcc. Second, we prove that the random Markov-Kakutani fixed point theorem implies the algebraic form of the known random Hahn-Banach theorem. Finally, we establish a more general strict separation theorem in a random locally convex module, which provides not only a more general geometric form of the random Hahn-Banach theorem but also another proof for the random Markov-Kakutani fixed point theorem. Therefore, as a byproduct, the work of this paper also shows that the algebraic and geometric forms of the random Hahn-Banach theorem are equivalent. It should be pointed out that the main challenge in this paper lies in overcoming noncompactness since a stably compact set is generally noncompact.

Acknowledgements

This work was supported by the National Natural Science Foundation of China (Grant No.12371141) and the Natural Science Foundation of Hunan Province of China (Grant No.2023JJ30642).


Author information

Qiang Tu
School of Mathematics and Statistics
Central South University
Changsha, Hunan 410083, China

qiangtu126@126.com

Xiaohuan Mu
School of Mathematics and Statistics
Central South University
Changsha, Hunan 410083, China

xiaohuanmu@163.com

Tiexin Guo
School of Mathematics and Statistics
Central South University
Changsha, Hunan 410083, China

tiexinguo@csu.edu.cn