Momentum-dependent electromagnetic T-matrix and dynamic effective properties of random media

We discuss the problem of the dynamic dielectric and magnetic response on the whole frequency range of a composite material. We derive exact one-body expressions of the momentum-dependent mean constitutive kernels, for an assembly of dielectric and magnetic spheres of finite size, on the basis of their T-matrix. The effective homogeneous-like constitutive constants are defined, and used in a coherent potential approximation. In a second step, we solve the dispersion relation in order to extract observable quantities.