부산대학교 도서관

The quantity that captures the asymptotic value of the maximum number of appearances of a given topological tree (a rooted tree with no vertices of outdegree 1) S with k leaves in an arbitrary tree with sufficiently large number of leaves is called the inducibility of S. Its precise value is known only for some specific families of trees, most of them exhibiting a symmetrical configuration. In an attempt to answer a recent question posed by Czabarka, Szekely, and the second author of this article, we provide bounds for the inducibility J (A5) of the 5-leaf binary tree A5 whose branches are a single leaf and the complete binary tree of height 2. It was indicated before that J(A5) appears to be 'close' to 1/4. We can make this precise by showing that 0.24707 ... [less than or equal to] J(A5) [less than or equal to] 0.24745 .... Furthermore, we also consider the problem of determining the inducibility of the tree Q4, which is the only tree among 4-leaf topological trees for which the inducibility is unknown. Keywords: inducibility, binary tree, ternary tree, leaf-induced subtree, maximum density, d-ary tree, topological tree
1 Introduction and previous results The study of graph inducibility was brought forward in 1975 by Pippenger and Golumbic, who investigated the maximum frequency of k-vertex simple graphs occurring as […]