Maximum Modulus of Independence Roots of Graphs and Trees

Abstract

The independence polynomial of a graph is the generating polynomial for the number of independent sets of each size and its roots are called independence roots. We bound the maximum modulus, $\mbox{maxmod}(n)$, of an independence root over all graphs on $n$ vertices and the maximum modulus, $\mbox{maxmod}_{T}(n)$, of an independence root over all trees on $n$ vertices in terms of $n$. In particular, we show that $$\frac{\log_3(\mbox{maxmod}(n))}{n}=\frac{1}{3}+o(1)$$ and $$\frac{\log_2(\mbox{maxmod}_{T}(n))}{n}=\frac{1}{2}+o(1).$$

24 pages, 3 figures, 1 table