The Shape of Symmetric Binary Trees

Abstract

Mandelbrot and Frame studied the geometry of self-contracting symmetric binary trees in which they stated that the height of such trees occurred at the branch tip of the path consisting of branches that alternate left and right. Taylor proved that this happens for both self-avoiding as well as self-contacting symmetric binary trees (if we ignore the height of the trunk and just consider the branch tips). In his commentary on the work by Mandelbrot and Frame, West gave an example of a self-overlapping tree in which this alternating left-right path does not give the highest point of the tree, and said that more analysis was needed. In this paper we show how such examples can be constructed for all but a countable number of angles. We also investigate the conditions for when the sides and bottom of a self-overlapping symmetric binary tree differ from what happens with self-avoiding and self-contacting trees.