On $H^\infty$ on the complement of C^{1+\alpha} curves
  Let $\rho$ be a quasiconformal mapping on the plane with complex dilatation $\mu$. We show that if $\mu$ satisfies a certain Carleson measure condition, then one can transfer $H^{\infty}$ on the upper half plane onto the corresponding space in the complement of the quasicircle $\Gamma=\rho(\mathbb{R})$, and that this condition on $\mu$ characterizes $C^{1+\alpha}$ curves. 
Mar\'ia Jos\'e Gonz\'alez Fuentes and Jos\'e Manuel Enr\'iquez de   Salamanca Garc\'ia
math.CV