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Re: Eigenvalues of a Hermitian matrix


Andrew W Steiner writes:
 > 	I want to calculate the derivative of a function of the
 > eigenvalues of a particular Hermitian matrix and so I need the eigenvalues
 > of several matrices whose entries are similar. Is there any way to
 > provide an inital guess to the gsl_eigen_herm routine if one is known?
 > 	From my understanding of the algorithm, the answer is no. In that
 > case, could anyone suggest an alternative? 

If you premultiply your perturbed matrices by V' (where V is the
unitary matrix of unperturbed eigenvectors) they will be close to
diagonal.  This might improve the computation of the eigenvalues.  The
same applies if you have only a guess for V.

It probably won't make much difference overall, but if it does let me
know.

regards
Brian


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