摘要:We show that if A is a closed linear operator defined in a Banach space X and there exist $t_{0} \geq 0$ and $M>0$ such that $\{(im)^{\alpha }\}_{ m > t_{0}} \subset \rho (A)$ , the resolvent set of A, and $$ \bigl\Vert (im)^{\alpha }\bigl(A (im)^{\alpha }I \bigr)^{-1} \bigr\Vert \leq M \quad \text{ for all } \vert m \vert > t_{0}, m \in \mathbb{Z}, $$ then, for each $\frac{1}{p}<\alpha \leq \frac{2}{p}$ and $1< p < 2$ , the abstract Cauchy problem with periodic boundary conditions $$ \textstyle\begin{cases} _{GL}D^{\alpha }_{t} u(t) Au(t) = f(t), & t \in (0,2\pi ); \\ u(0)=u(2\pi ), \end{cases} $$ where $_{GL}D^{\alpha }$ denotes the Grünwald–Letnikov derivative, admits a normal 2π-periodic solution for each $f\in L^{p}_{2\pi }(\mathbb{R}, X)$ that satisfies appropriate conditions. In particular, this happens if A is a sectorial operator with spectral angle $\phi _{A} \in (0, \alpha \pi /2)$ and $\int _{0}^{2\pi } f(t)\,dt \in \operatorname{Ran}(A)$ .