Unicritical Blaschke products and domains of ellipticity

Abstract

Elliptic M\"obius transformations of the unit disk are those for which there is a fixed point in $\mathbb{D}$. It is not hard to classify which M\"obius transformations are elliptic in terms of the parameters. The set of parameters can be identified with the solid torus $S^1 \times \mathbb{D}$, and the set of elliptic parameters is called the domain of ellipticity. In this paper, we study the domain of ellipticity for non-trivial unicritical Blaschke products. We will also study the set corresponding to the Mandelbrot set for this family, and show how it can be obtained from the domain of ellipticity by adding one point.