Concerning the Eigenvalues of $DA$ under Variations of the Entries of D and A
Darald J. Hartfiel · SIAM Journal on Mathematical Analysis · 1980
Let A be a positive definite matrix and D a nonsingular, nonnegative diagonal matrix. This paper is a study of the eigenvalues of $DA$ under variations between zero and infinity of specified entries of D and A. Intervals containing these eigenvalues are determined and these intervals are seen to be the best possible.