Hardy spaces and the Szeg\H{o} projection of the non-smooth worm domain $D'_\beta$

Abstract

We define Hardy spaces $H^p(D'_\beta)$ on the non-smooth worm domain $D'_\beta=\{(z_1,z_2)\in\mathbb{C}^2:|Im z_1-\log |z_2|^2|<\frac{\pi}{2}, |\log |z_2|^2|<\beta-\frac{\pi}{2}\}$ and we prove a series of related results such as the existence of boundary values on the distinguished boundary $\partial D'_\beta$ of the domain and a Fatou-type theorem (i.e. pointwise convergence to the boundary values). Thus, we study the Szeg\H{o} projection operator $\widetilde{S}$ and the associated Szeg\H{o} kernel $K_{D'_\beta}$. More precisely, if $H^p(\partial D'_\beta)$ denotes the space of functions which are boundary values for functions in $H^p(D'_\beta)$, we prove that the operator $\widetilde{S}$ extends to a bounded linear operator $$ \widetilde{S}: L^p(\partial D'_\beta)\to H^p(\partial D'_\beta) $$ for every $p\in(1,+\infty)$ and $$ \widetilde{S}: W^{k,p}(\partial D'_\beta)\to W^{k,p}(\partial D'_\beta) $$ for every $k>0$. Here $W^{k,p}$ denotes the Sobolev space of order $k$ and underlying $L^p$ norm. As a consequence of the $L^p$ boundedness of $\widetilde{S}$, we prove that $H^p(D'_\beta)\cap\mathcal{C}(\overline{D'_\beta})$ is a dense subspace of $H^p(D'_\beta)$.