Distortion of quasiconformal maps in terms of the quasihyperbolic metric

We extend a theorem of Gehring and Osgood from 1979 - relating to the distortion of the quasihyperbolic metric by a quasiconformal mapping between Euclidean domains - to the setting of metric measure spaces of Q-bounded geometry. When the underlying target space is bounded, we require that the boundary of the image has at least two points. We show that even in the manifold setting, this additional assumption is necessary. (c) 2013 Elsevier Inc. All rights reserved.