Multifractal formalism for expanding rational semigroups and random complex dynamical systems

We consider the multifractal formalism for the dynamics of semigroups of rational maps on the Riemann sphere and random complex dynamical systems. We elaborate a multifractal analysis of level sets given by quotients of Birkhoff sums with respect to the skew product associated with a semigroup of rational maps. Applying these results, we perform a multifractal analysis of the H"older regularity of limit state functions of random complex dynamical systems.