# Local semicircle law under fourth moment condition

## TL;DR

This paper extends the local semicircle law for Wigner matrices to the case where only the fourth moment is finite, removing the previous need for a higher moment condition, and discusses implications for spectral convergence and eigenvector localization.

## Contribution

It proves that the local semicircle law holds under only the finite fourth moment condition, improving previous results that required a higher moment assumption.

## Key findings

- The local semicircle law holds with only finite fourth moment.
- Convergence rates of the empirical spectral distribution are established.
- Results on eigenvalue localization and eigenvector delocalization are provided.

## Abstract

We consider a random symmetric matrix ${\bf X} = [X_{jk}]_{j,k=1}^n$ with upper triangular entries being independent random variables with mean zero and unit variance. Assuming that $\max_{jk} {\mathbb E} |X_{jk}|^{4+\delta} < \infty, \delta > 0$, it was proved in [G\"otze, Naumov and Tikhomirov, Bernoulli, 2018] that with high probability the typical distance between the Stieltjes transforms $m_n(z), z = u + i v$, of the empirical spectral distribution (ESD) and the Stieltjes transforms $m_{sc}(z)$ of the semicircle law is of order $(nv)^{-1} \log n$. The aim of this paper is to remove $\delta>0$ and show that this result still holds if we assume that $\max_{jk} {\mathbb E} |X_{jk}|^{4} < \infty$. We also discuss applications to the rate of convergence of the ESD to the semicircle law in the Kolmogorov distance, rates of localization of the eigenvalues around the classical positions and rates of delocalization of eigenvectors.