Rough Interfaces Beyond the Gaussian Approximation
  We compare predictions of the Capillary Wave Model with Monte Carlo results for the energy gap and the interface energy of the 3D Ising model in the scaling region. Our study reveals that the finite size effects of these quantities are well described by the Capillary Wave Model, expanded to two-loop order (one order beyond the Gaussian approximation). 
M. Caselle, F. Gliozzi, R. Fiore, M. Hasenbusch, K. Pinn, S. Vinti