Concentration of the spectral norm of Erdős-Rényi random graphs

Abstract: We present results on the concentration properties of the spectral norm $|A_p|$ of the adjacency matrix $A_p$ of an Erd\H{o}s-R\'enyi random graph $G(n,p)$. First we consider the Erd\H{o}s-R\'enyi random graph process and prove that $|A_p|$ is uniformly concentrated over the range $p\in [C\log n/n,1]$. The analysis is based on delocalization arguments, uniform laws of large numbers, together with the entropy method to prove concentration inequalities. As an application of our techniques we prove sharp sub-Gaussian moment inequalities for $|A_p|$ for all $p\in [c\log^3n/n,1]$ that improve the general bounds of Alon, Krivelevich, and Vu (2001) and some of the more recent results of Erd\H{o}s et al. (2013). Both results are consistent with the asymptotic result of F\"uredi and Koml\'os (1981) that holds for fixed $p$ as $n\to \infty$.