Compactifications and measures for rational maps

Jan Kiwi, Hongming Nie

Published 2024-12-27Version 1

We study extensions of the measure of maximal entropy to suitable compactifications of the parameter space and the moduli space of rational maps acting on the Riemann sphere. For parameter space, we consider a space which resolves the discontinuity of the iterate map. We show that the measure of maximal entropy extends continuously to this resolution space. For moduli space, we consider a space which resolves the discontinuity of the iterate map acting on its geometric invariant theory compactification. We show that the measure of maximal entropy, barycentered and modulo rotations, also extends continuously to this resolution space. Thus, answering in the positive a question raised by DeMarco. A main ingredient is a description of limiting dynamics for some sequences.