The $H^p(\mathbb{Z}^n)-H^q(\mathbb{Z}^n)$ boundedness of discrete Riesz potential

Abstract: In [J. Class. Anal., vol. 26 (1) (2025), 63-76], we proved that the discrete Riesz potential $I_{\alpha}$ is a bounded operator $H^p(\mathbb{Z}^n) \to H^q(\mathbb{Z}^n)$ for $\frac{n-1}{n} < p \leq 1$, $\frac{1}{q} = \frac{1}{p} - \frac{\alpha}{n}$ and $0 < \alpha < n$. In this note, we extend such boundedness on the full range $0 < p \leq 1$.