Mode-coupling and renormalization group results for the noisy Burgers equation

Abstract

We investigate the noisy Burgers equation (Kardar–Parisi–Zhang equation in 1+1 dimensions) using the dynamical renormalization group (to two–loop order) and mode–coupling techniques. The roughness and dynamic exponent are fixed by Galilean invariance and a fluctuation–dissipation theorem. The fact that there are no singular two–loop contributions to the two–point vertex functions supports the mode–coupling approach, which can be understood as a self–consistent one–loop theory where vertex corrections are neglected. Therefore, the numerical solution of the mode coupling equations yields very accurate results for the scaling functions. In addition, finite–size effects can be studied. Furthermore, the results from exact Ward identities, as well as from second–order perturbation theory permit the quantitative evaluation of the vertex corrections, and thus provide a quantitative test for the mode–coupling approach. It is found that the vertex corrections themselves are of the order one. Surprisingly, however, their effect on the correlation function is substantially smaller.