The Quarterly Journal of Mathematics Advance Access published online on March 3, 2009
The Quarterly Journal of Mathematics, doi:10.1093/qmath/hap007
STRETCHING CONVEX DOMAINS AND THE HYPERBOLIC METRIC
Department of Mathematics, Purdue University, Indiana, USA

Department of Mathematics, National University of Ireland, Cork, Ireland
Corresponding author. E-mail: t.carroll{at}ucc.ie
Received 16 August 2008;
revised 19 January 2009
| Abstract |
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It is shown that the log-convexity of the density of the hyperbolic metric in a convex planar domain leads to a pointwise comparison between the density of the hyperbolic metric in a convex domain D and that in a domain obtained by stretching D. Applications of this result are given, including estimates for the density of the hyperbolic metric in the domain interior to an ellipse and a lower bound for the density of the hyperbolic metric in a convex domain in terms of the density in a comparison strip. Connections are made with the convexity of related functions on convex regions in space.