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Pré-Publication, Document De Travail Année : 2009

The eigenvalues and eigenvectors of finite, low rank perturbations of large random matrices

Résumé

We consider the eigenvalues and eigenvectors of finite, low rank perturbations of random matrices. Specifically, we prove almost sure convergence of the extreme eigenvalues and appropriate projections of the corresponding eigenvectors of the perturbed matrix for additive and multiplicative perturbation models. The limiting non-random value is shown to depend explicitly on the limiting spectral measure and the assumed perturbation model via integral transforms that correspond to very well known objects in free probability theory that linearize non-commutative free additive and multiplicative convolution. Furthermore, we uncover a remarkable phase transition phenomenon whereby the large matrix limit of the extreme eigenvalues of the perturbed matrix differs from that of the original matrix if and only if the eigenvalues of the perturbing matrix are above a certain critical threshold. This critical threshold is intimately related to the same aforementioned integral transforms and our proof techniques bring this connection and the origin of the phase transition into exceedingly sharp focus. Consequently, our results extend the class of `spiked' random matrix models about which such predictions can be made well beyond the Gaussian, Wishart and Jacobi random ensembles found in the literature. We examine the impact of this eigenvalue phase transition on the associated eigenvectors and provide a sufficient condition when an analogous phase transition in the eigenvectors is observed. Various extensions of our results to the problem of non extreme eigenvalues are discussed.
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Dates et versions

hal-00423593 , version 1 (12-10-2009)
hal-00423593 , version 2 (28-04-2010)
hal-00423593 , version 3 (27-12-2010)

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Florent Benaych-Georges, Raj Rao. The eigenvalues and eigenvectors of finite, low rank perturbations of large random matrices. 2009. ⟨hal-00423593v2⟩
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