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Tracy-Widom distribution for the edge eigenvalues of elliptical model

Abstract

In this paper, we study the largest eigenvalues of sample covariance matrices with elliptically distributed data. We consider the sample covariance matrix Q=YY,Q=YY^*, where the data matrix YRp×nY \in \mathbb{R}^{p \times n} contains i.i.d. pp-dimensional observations yi=ξiTui,  i=1,,n.\mathbf{y}_i=\xi_iT\mathbf{u}_i,\;i=1,\dots,n. Here ui\mathbf{u}_i is distributed on the unit sphere, ξiξ\xi_i \sim \xi is independent of ui\mathbf{u}_i and TT=ΣT^*T=\Sigma is some deterministic matrix. Under some mild regularity assumptions of Σ,\Sigma, assuming ξ2\xi^2 has bounded support and certain proper behavior near its edge so that the limiting spectral distribution (LSD) of QQ has a square decay behavior near the spectral edge, we prove that the Tracy-Widom law holds for the largest eigenvalues of QQ when pp and nn are comparably large.

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