Existence and Approximations for Order-Preserving Nonexpansive Semigroups over $\mathrm{CAT}(\kappa )$ Spaces

Abstract

In this paper, we discuss the fixed point property for an infinite family of order-preserving mappings which satisfy the Lipschitzian condition on comparable pairs. The underlying framework of our main results is a metric space of any global upper curvature bound $\kappa \in \mathbb{R}$, i.e., a $\mathrm{CAT}(\kappa )$ space. In particular, we prove the existence of a fixed point for a nonexpasive semigroup on comparable pairs. Then, we propose and analyze two algorithms to approximate such a fixed point.