Smooth bounded planar domain is tangent to the unit sphere

37 Views Asked by At

Let $D\subset\mathbb{C}$ be a smooth bounded planar domain. Let $p\in\partial {D}$ be any boundary point. Then My Teacher said $D$ is tangent to the unit sphere $S^{1}$ at $p$ up to any order, up to holomorphic change of coordinates. Recall $D$ is tangent to the unit sphere $S^{1}$ at $p$, up to order $n\in\mathbb{N}$ means there exists a local defining function $\phi:(p\in)U_{p}\to\mathbb{R}$ of $D$ corresponding to $p$ such that in an open set $U_{p}$ of $p$, $$\dfrac{\partial^{k}\phi(p)}{\partial z^{\alpha}\partial\overline{z}^{\beta}}=\dfrac{\partial^{k}\phi_{\mathbb{D}}(p)}{\partial z^{\alpha}\partial\overline{z}^{\beta}} $$ for all $|\alpha|+|\beta|\leq n$, where $\phi_{\mathbb{D}}$ is a defining function of unit disc $\mathbb{D}$. I have tried using the Riemann mapping theorem, but I am not able to do it. It would be a great help if someone could provide any sort of help. Thanks in advance.