Nonasymptotic critical behaviour from field theory for Ising like systems in the homogeneous phase : theoretical framework

We report results of a precise nonlinear renormalization group (RG) treatment of the ϕ4 model in three dimensions. We give the complete set of usually measurable quantities above Tc (the correlation length ξ, the susceptibility χ and the specific heat C) for Ising like systems as explicit numerical functions of temperature. We discuss the correspondence between the fundamental hypothesis of the RG and the adjustable parameters (only three) needed for a comparison with experiments.