Symmetries for Julia sets of rational maps

Abstract

Since the 1980s, much progress has been done in completely determining which functions share a Julia set. The polynomial case was completely solved in 1995, and it was shown that the symmetries of the Julia set play a central role in answering this question. The rational case remains open, but it was already shown to be much more complex than the polynomial one. Here, we offer partial extensions to Beardon's results on the symmetry group of Julia sets, and discuss them in the context of singularly perturbed maps.

11 pages, 3 figure. Corrected a mistake in Lemma 2.6 (previously 2.3), added and expanded results on potentials and added figures to Section 3