Inequalities on a Class of Function Sets

Abstract

We prove a functional extension of an exponential inequality originally proposed by Bin Zhao and proved by Xiaosheng Mou. The main result asserts that if $α_1\leq \cdots\leq α_n$ and $\sum_{k=1}^n α_k=0$, then \[ \sum_{k=1}^n ϕ(kα_k)\geq 0 \] for every odd function $ϕ$ that is increasing and convex on $[0,\infty)$. The proof is based on a truncated-sum comparison and the stop-loss characterization of the increasing convex order. As consequences, we recover the original exponential inequality and obtain polynomial and integral variants.