On a question of boyle and handelman concerning eigenvalues of nonnegative matrices
Title:
On a question of boyle and handelman concerning eigenvalues of nonnegative matrices
Author:
Koltracht, I. Neumann, M. Xiao, D.
Appeared in:
Linear & multilinear algebra
Paging:
Volume 36 (1993) nr. 2 pages 125-140
Year:
1993-11
Contents:
Let A be an n × n nonnegative matrix whose eigenvalues are λ1,…,λn, with λ1 its Perron root. Keilson and Styan and, more recently Ashley, have shown that [image omitted] . Boyle and Handelman in their paper on the inverse eigenvalue problem for nonnegative matrices ask whether this inequality can be strengthened as follows: Suppose λ1,…,λk are the nonzero eigenvalue of A, Then does the inequlity [image omitted] , hold? In this paper we partially answer their question by considering a set of p complex numbers (not necessarily the eigenvalues of a nonnegative matrix) μ1,…,μp such that μ1≥ max1≤i≤p∣μi∣ and such that [image omitted] ? Using Newton's identities for symmetric polynomials we show that the answer to this question is in the affirmative when p≤5. For p≥ 6, we show that there exists a constant [image omitted] , such that the inequality holds for all μ≥Cpμ1. Furthermore cp→ 1 as p→∞. Thus at least the same conclusions hold for the question posed by Boyle and Handelman. In the case when all the μi' are real, the fact that when [image omitted] , is an easY consequence of an additional observation by Keilson and Styan.