Abstract
We extend the classical Schwarz–Pick inequality to the class of harmonic mappings between the unit disk and a Jordan domain with given perimeter. It is intriguing that the extremals in this case are certain harmonic diffeomorphisms between the unit disk and a convex domain that solve the Beltrami equation of second order.
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I am grateful to the referee for useful suggestions and corrections.
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Kalaj, D. A Sharp Inequality for Harmonic Diffeomorphisms of the Unit Disk. J Geom Anal 29, 392–401 (2019). https://doi.org/10.1007/s12220-018-9996-3
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DOI: https://doi.org/10.1007/s12220-018-9996-3