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New York Journal of Mathematics
Volume 31 (2025), 1543-1564

  

Qiang Tu, Xiaohuan Mu, Tiexin Guo, Guang Yang, and Yuanyuan Sun

The random Kakutani fixed point theorem in random normed modules

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Published: November 12, 2025.
Keywords: Random normed modules, Random Kakutani fixed point theorem, Random sequentially compact sets, upper semicontinuous set-valued mappings.
Subject [2010]: 46H25, 47H10, 46A22.

Abstract
Based on the recently developed theory of random sequential compactness, we prove the random Kakutani fixed point theorem in random normed modules: if G is a random sequentially compact L0-convex subset of a random normed module, then every σ-stable Tc-upper semicontinuous mapping F:G -> 2G \ {∅} such that F(x) is closed and L0-convex for each x in G, has a fixed point. This is the first fixed point theorem for set-valued mappings in random normed modules, providing a random generalization of the classical Kakutani fixed point theorem as well as a set-valued extension of the noncompact Schauder fixed point theorem established in [Guo et al., Math. Ann. 391(3), 3863--3911 (2025)].

Acknowledgements

This work was supported by the National Natural Science Foundation of China (Grant Nos.12371141, 12426645, 12426654) 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

Guang Yang
School of Mathematics and Statistics
Central South University
Changsha, Hunan 410083, China

guangyang@163.com

Yuanyuan Sun
School of Mathematics and Statistics
Central South University
Changsha, Hunan 410083, China

yuanyuansun1205@163.com