Differentials of Eigenvalues and Eigenvectors in Undamped Discrete Systems under Alternative Normalizations

First-order differentials of a (simple) eigenvalue and the associated eigenvector in an undamped discrete system are investigated. We provide closed-form expressions under three alternative normalizations, namely the customary mass normalization, unit-length normalization and the normalization obtained setting an element equal to 1. The proposed formulas have no pretension to be computationally efficient in large systems, but may be useful for the interpretation of the results.