A Characterization of hyperbolic potentials of rational maps

Consider a rational map $f$ of degree at least 2 acting on its Julia set $J(f)$, a H\"older continuous potential $\phi: J(f)\rightarrow \R$ and the pressure $P(f,\phi). In the case where$\sup_{J(f)}\phi<P(f,phi)$, the uniqueness and stochastic properties of the corresponding equilibrium states have been extensively studied. In this paper we characterize those potentials$\phi$for which this property is satisfied for some iterate of$f$, in terms of the expanding properties of the corresponding equilibrium states. A direct consequence of this result is that for a nonuniformly hyperbolic rational map every H\"older continuous potential has a unique equilibrium state and that this measure is exponentially mixing.