Depinning transition at the upper critical dimension

We study the effect of quenched random field disorder on a driven elastic interface close to the depinning transition at the upper critical dimension d(c)=4 using the functional renormalization group. We have found that the displacement correlation function behaves with distance x as (ln xLambda(0))(2/3) for large x. Slightly above the depinning transition the force-velocity characteristics are described by the equation vsimilar tof\ln f\(2/9), while the correlation length behaves as L(v)similar tof(-1/2)\ln f\(1/6), where f=F/F-c-1 is the reduced driving force.