Some invariant classes for parabolic renormalization in the multicritical case

Abstract

Parabolic renormalization associates to a holomorphic map f with a parabolic fixed point another holomorphic map with a parabolic fixed point. This procedure is essential for understanding the phenomenon of parabolic enrichment, which occurs when one perturbs f appropriately. Shishikura defined in [Shi98] (see also [LY14]) a class of maps that is stable under this parabolic renormalization operator. These maps have only one critical point in their immediate basins. We extend here this result to the more general classes of maps conjugated on their immediate basins to finite Blaschke products. For these classes, we introduce an analogue of Milnor's mapping schemes [Mil12] and describe the action of parabolic renormalization on the scheme. This shall be a starting point to the fine study of perturbation of these bigger classes of maps.