Jordan domains with a rectifiable arc in their boundary
We show that if an open arc J of the boundary of a Jordan domain $Ω$ is rectifiable, then the derivative $Φ$' of the Riemann map $Φ: D\rightarrow Ω$ from the open unit disk D onto $Ω$ behaves as an $H^1$ function when we approach the arc $Φ^{-1}(J^{\prime})$,where $J^{\prime}$ is any compact subarc of $J$. "