# zbMATH — the first resource for mathematics

On almost periodic solutions of the differential equation $$x''(t)=Ax(t)$$ in Hilbert spaces. (English) Zbl 1006.34052
Summary: The author proves the almost-periodicity of solutions to the equation $$x''(t)= Ax(t)$$ when the linear operator $$A$$ satisfies an inequality of the form $$\text{Re}(Ax,x)\geq 0$$.

##### MSC:
 34G10 Linear differential equations in abstract spaces
##### Keywords:
almost-periodicity; solutions
Full Text: