Schwarz's lemma for circle packings

Burt Rodin* Department of Mathematics, University of California, La Jolla, CA 92093, USA 1. Introduction Conformal mappings can be approximated by circle packing isomorphisms; this is proved in [-10]. Roughly speaking (see Sect. 5 for a more detailed description), a bounded region f2 is almost filled by e-circles 7 from the regular hexagonal e-circle packing of the plane. Denote this approximate circle pack- ing of Q by Q=. By results of Andreev and Thurston, there is a combinatorially isomorphic circle packing D+ of the unit disk D. Denote this isomorphism, suitably normalized, by 7~--,7': f2=--*D=. Let f= be the piecewise linear quasicon- formal mapping determined by the associated triangulations. As e~0, f~ con- verges uniformly on compacta to the Riemann mapping function f: f2~D. Let