Bernoulli flow for Erdős-Rényi graphs

Abstract

We study the eigenvalues and eigenvectors of the adjacency matrix $A$ of the Erdős-Rényi graph $\mathbb{G}(N,p)$ in the regime $Np\gg (\log N{)}^2$. We establish optimal isotropic delocalization for the bulk eigenvectors $\mathbf{u}$, meaning that $⟨\mathbf{v},\mathbf{u}{⟩}^2\le \frac{C\log N}{N}$ with very high probability for any deterministic normalized $\mathbf{v}$. In addition, we prove local spectral universality in the bulk by showing that the local spectral statistics coincide with those of the GOE. The main tool of our proof is a local law for the resolvent of $A$, down to optimal spectral scales and with optimal error bounds. Its proof relies on a new approach to local laws that we call the Bernoulli flow. It is a characteristic flow method in which the usual Brownian process is replaced by a Bernoulli process, where each edge of the graph forms an independent Markov process that jumps at unit rate from closed to open. The spectral parameter flows according to a suitably constructed matrix-valued Bernoulli characteristic flow.