Abstract
We prove that the elastic fields within a generic nonlinear and anisotropic inhomogeneity embedded in a (linear and anisotropic) matrix are uniform. We apply this general result to the specific case of a dispersion of isotropic nonlinear spheres and we obtain a universal mixing scheme for the Landau coefficients. This scheme describes a complex scenario frequently found in material physics problems, where possible strong amplifications of the nonlinearities may arise in some given conditions.