Solution
= Solution
The <Campanato space> $\mathcal L^{p,\mu}(\Omega)$ consists of $f\in L^p(\Omega)$ for which
$$
[f]_{\mathcal L^{p,\mu}}^p
=\sup_{x_0,r}r^{-\mu}\int_{\Omega\cap B_r(x_0)}
|f-f_{\Omega\cap B_r(x_0)}|^p<\infty,
$$
where $f_E=|E|^{-1}\int_Ef$. On a smooth bounded domain,
$$
\mathcal L^{p,n+p\alpha}(\Omega)=C^{0,\alpha}(\overline\Omega)
$$
with equivalent norms for $0<\alpha\leq1$.