Mean Value and comparative convex functions

Abstract

During the study of the topic of limit summability of functions (introduced by the author in 2001), we encountered some types of functions that are related to the mean value theorem. In this paper, we formally define mean value and pointwise MV-functions associated with a given real function and extend some aspects of the mean value theorem and properties. Also, we introduce and study an induced conception which we call comparative convexity (and concavity). As many applications of the study, we prove some uniqueness conditions for related functional equations and completely solve several functional inequalities. It is worth noting that there remain some important open problems and questions for future studies of the topic.