Decay of covariances , uniqueness of ergodic component and scaling limit for a class of ∇ φ systems with non - convex potential

We consider a gradient interface model on the lattice with interaction potential which is a non-convex perturbation of a convex potential. Using a technique which decouples the neighboring vertices sites into even and odd vertices, we show for a class of non-convex potentials: the uniqueness of ergodic component for ∇φ-Gibbs measures, the decay of covariances, the scaling limit and the strict convexity of the surface tension.