Let r<1 and s be positive numbers. We prove that a Banach space X satisfies the M(r,s)-inequality (i.e.//x***//>r//x***//+s//x***-x***// x***CX***, where is the canonical projection of X*** onto X*) if and only if the unit sphere Sx of X has the following property: whenever s>0, X展开▼
机译：令r <1和s为正数。我们证明Banach空间X满足M（r，s）不等式（即// x *** //> r // x *** // + s // x ***-x *** // x *** CX ***，当且仅当X的单位球面Sx具有以下属性时，才是X ***在X *上的规范投影：每当s> 0，X 展开▼
