Schoenflies solutions of conformal boundary values may fail to be Sobolev

Abstract

We show that there exists a planar Jordan domains $\Omega$ with boundary of Hausdorff dimension $1$ such that, for any conformal maps $\varphi \colon \mathbb D \to \Omega$, any homeomorphic extension of $\varphi$ or $\varphi^{-1}$ to the entire plane is not in $W^{1,\,1}_{\rm loc}$ (or even not in $BV_{\rm loc}$).