An N-dimensional version of the Beurling-Ahlfors extension

Abstract

We extend delta-monotone quasiconformai mappings from dimension n to n + 1 while preserving both monotonicity and quasiconformality. This gives an analytic proof of the extendability of quasiconformal mappings that can be factored into bi-Lipschitz and delta-monotone mappings. In the case n = 1 our approach yields a refinement of the Beurling-Ahlfors extension.