In fact I've ask this question on math.stackexchange already, and was advocated to ask here. I do hope to get a proof for it.

For a hermitian matrix R and a diagonal one Q, is there any relationship between eigenvalues/eigenvectors of R and QRQ?

To be specific, assuming the eigenvalue decomposition of R is R=VDV*, then can the eigenvalues/eigenvectors of QRQ be represented by V, D & Q?

Thanks a lot!