Abstract:
We obtain an integral representation for the solution to the Cauchy problem
$$
\begin {gathered}
\frac{dv}{dt}=\mathbb B_1^2v+\frac 12b(t)(\mathbb B_2\mathbb B_1
+\mathbb B_1\mathbb B_2)v+c(t)\mathbb B_2^2v,
\quad v(0)=v_0,
\end {gathered}
$$
where the operators $\mathbb{B}_1 $ and $\mathbb{B}_2 $ are the infinitesimal generators of strongly continuous groups and $\mathbb B_1\mathbb B_2-\mathbb B_2\mathbb B_1=k\mathbf 1$, $k\ne0$. For the case in which $k=ik_1$, $k_1\in\mathbb R$, it is proved that the solution tends to zero as $t\to+\infty$.