Long-wavelength iteration scheme and scalar-tensor gravity

Inhomogeneous and anisotropic cosmologies are modeled within the framework of scalar-tensor gravity theories. The inhomogeneities are calculated to third order in the so-called long-wavelength iteration scheme. We write the solutions for general scalar coupling and discuss what happens to the third-order terms when the scalar-tensor solution approaches at first order the general relativistic one. We work out in some detail the case of Brans-Dicke coupling and determine the conditions for which the anisotropy and inhomogeneity decay as time increases. The matter is taken to be that of perfect fluid with a baryotropic equation of state.