The universality principle for spectral distributions of sample covariance matrices

Abstract

We derive the universality principle for empirical spectral distributions of sample covariance matrices and their Stieltjes transforms. This principle states the following. Suppose quadratic forms of random vectors $y_p$ in $R^p$ satisfy a weak law of large numbers and the sample size grows at the same rate as $p$. Then the limiting spectral distribution of corresponding sample covariance matrices is the same as in the case with conditionally Gaussian $y_p$. This result is generalized for $m$-dependent martingale difference sequences and $m$-dependent linear processes.