Rigidity of Infinite (Circle) Packings
The nerve of a packing is a graph that encodes its combinatorics. The vertices of the nerve correspond to the packed sets, and an edge occurs between two vertices in the nerve precisely when the corresponding sets of the packing intersect.
The nerve of a circle packing and other well-behaved packings, on the sphere or in the plane, is a planar graph. It was an observation of Thurston [Th1, Chapter 1; 13, Th2] that Andreev’s theorem [An1, An2] implies that given a finite planar graph, there exists a packing of (geometric) circles on the sphere whose nerve is the given graph. We refer to this fact as the circle packing theorem. The circle packing theorem also has a uniqueness part to it: if the graph is actually (the 1-skelaton of) a triangulation, then the circle packing is unique up to Möbius transformations.
KeywordsPlanar Graph Double Cover Circle Packing Rigidity Theorem Hexagonal Packing
I am deeply thankful to my teachers Bill Thurston and Peter Doyle, and to Richard Schwartz, Burt Rodin, and Zheng-Xu He for stimulating discussions relating to packings.
- [CR]I. Carter and B. Rodin, An inverse problem for circle packing and conformal mapping, preprint.Google Scholar
- [He1]Zheng-Xu He, An estimate for hexagonal circle packings, J. Differential Geom. (to appear).Google Scholar
- [He2]—, Solving Beltrami equations by circle packing, Trans. Amer. Math. Soc. (to appear).Google Scholar
- [Sch1]O. Schramm, Packing two-dimensional bodies with prescribed combinatorics and applications to the construction of conformal and quasiconformal mappings, Ph.D. thesis, Princeton, 1990.Google Scholar
- [Sch2]—, Uniqueness and existence of packings with specified combinatorics, Israel J. Math. (to appear).Google Scholar
- [Th1]W. P. Thurston, The geometry and topology of 3-manifolds, Princeton Univ. Lecture Notes, Princeton, NJ.Google Scholar
- [Th2]—, The finite Riemann mapping theorem, invited talk at the International Symposium in Celebration of the Proof of the Bieberbach Conjecture, Purdue University, March 1985.Google Scholar