文摘
Let V be a convex subset of a normed space and let a nondecreasing function α : [0, ∞) → [0, ∞) be given. A function f : V ? \mathbbR{f : V \rightarrow \mathbb{R}} is called α-midconvex if f(\fracx+y2 ) ¡ê \fracf(x)+f(y)2+a(||x-y||) for x,y ? V.f\left(\frac{x+y}{2} \right)\leq \frac{f(x)+f(y)}{2}+\alpha(\|x-y\|) \quad \,{\rm for}\, x,y\in V.