The multiplier spectrum morphism is generically injective

In this paper, we consider the multiplier spectrum of periodic points, which is a natural morphism defined on the moduli space of rational maps on the projective line. A celebrated theorem of McMullen asserts that aside from the well-understood flexible Lattès family, the multiplier spectrum morphism is quasi-finite. In this paper, we strengthen McMullen’s theorem by showing that the multiplier spectrum morphism is generically injective. This answers a question of McMullen and Poonen.