Local semicircle law under moment conditions. Part II: Localization and delocalization

Abstract: We consider a random symmetric matrix ${\bf X} = [X_{jk}]{j,k=1}^n$ with upper triangular entries being independent identically distributed random variables with mean zero and unit variance. We additionally suppose that $\mathbb E |X{11}|^{4 + \delta} =: \mu_{4+\delta} < C$ for some $\delta > 0$ and some absolute constant $C$. Under these conditions we show that the typical Kolmogorov distance between the empirical spectral distribution function of eigenvalues of $n^{-1/2} {\bf X}$ and Wigner's semicircle law is of order $1/n$ up to some logarithmic correction factor. As a direct consequence of this result we establish that the semicircle law holds on a short scale. Furthermore, we show for this finite moment ensemble rigidity of eigenvalues and delocalization properties of the eigenvectors. Some numerical experiments are included illustrating the influence of the tail behavior of the matrix entries when only a small number of moments exist.