Inertia of Kwong matrices

Abstract

Let $r$ be any real number and for any $n$ let $p_1,\dots ,p_n$ be distinct positive numbers. A Kwong matrix is the $n\times n$ matrix whose $(i,j)$ entry is $(p_i^r+p_j^r)/(p_i+p_j).$ We determine the signatures of eigenvalues of all such matrices. The corresponding problem for the family of Loewner matrices $\left[\begin{array}{c}(p_i^r-p_j^r)/(p_i-p_j)\end{array}\right]$ has been solved earlier.

9 pages