Local four-point vertex near the Mott transition

We study the local four-point vertex of the Hubbard model near the Mott transition using dynamical mean-field theory (DMFT). We employ the numerical renormalization group (NRG) as impurity solver in the DMFT loop. We use NRG and symmetrized equations of motion to compute the four-point vertex in both the Matsubara and Keldysh formalisms. We analyze characteristic signatures of the Mott transition in the vertex. We also study the vertex asymptotic classes and the single-boson exchange decomposition of the four-point vertex near the Mott transition.