Banach空间中余弦算子函数生成元的有界性

A Note on Boundness of Generators of Cosine Operator Functions in Banach Spaces

A是 Banach空间 X中余弦算子函数 C(t) ,t∈ R,和正弦算子函数 S(t) ,t∈ R,的生成元 .本文证明了 ,对每个 f∈ C([0 ,T];X) ,连续函数u,u(t) =∫t0 S(t-s) f (s) ds,t∈ [0 ,T]是二阶非齐次 0初值问题 u″=Au+f 的强解的充要条件是 :A是空间 X中的有界算子 .

Let A be the generator of cosine operator function C(t),t∈R, and sine operator function S(t), t∈R, in Banach space X . This note proves that for every f∈C(\;X), the continuous functionu,u(t)=∫ t 0S(t-s)f(s) d s, t∈is a strong (classical) solution of the second inhomogeneous zero initial value problem u″=Au+f, in \, iff A is a bounded operator in X.