Interpolating quasiregular power mappings
Jack Burkart, Alastair N. Fletcher, Daniel A. Nicks
TL;DR
This work constructs a transcendental-type quasiregular map in $\mathbb{R}^3$ whose quasi-Fatou set contains bounded hollow components and whose Julia set features spherical components, achieved through a novel ring-based interpolation between power maps of different degrees. Central to the method is a quasiregular interpolation in round rings that transitions from $p_d$ to $p_{3d}$, combined with Zorich maps and a gluing step to ensure global coherence and growth control. The authors build a global map by layering interpolants and power-type blocks across concentric rings, yielding a dynamical picture with wandering hollow quasi-Fatou components bounded by spherical Julia components, and provide a mechanism to realize prescribed growth rates. Overall, the paper delivers the first higher-dimensional example in which $QF(f)$ contains bounded hollow components and multiple spherical Julia components, advancing understanding of quasi-Fatou/Julia structures in dimension three and offering flexible construction techniques for growth behavior.
Abstract
We construct a quasiregular mapping in $\mathbb{R}^3$ that is the first to illustrate several important dynamical properties: the quasi-Fatou set contains wandering components; these quasi-Fatou components are bounded and hollow; and the Julia set has components that are genuine round spheres. The key tool in this construction is a new quasiregular interpolation in round rings in $\mathbb{R}^3$ between power mappings of differing degrees on the boundary components. We also exhibit the flexibility of constructions based on these interpolations by showing that we may obtain quasiregular mappings which grow as quickly, or as slowly, as desired.
