Statistical field theory for a multicomponent fluid: The collective variables approach

Using the collective variables (CV) method the basic relations of statistical field theory of a multicomponent non-homogeneous fluids are reconsidered. The corresponding CV action depends on two sets of scalar fields - fields ${\rho }_{\alpha }$ connected to the local density fluctuations of the $\alpha$th species of particles and fields ${\omega }_{\alpha }$ conjugated to ${\rho }_{\alpha }$. The explicit expressions for the CV field correlations and their relation to the density correlation functions are found. The perturbation theory is formulated and a mean field level (MF) of the theory is considered in detail.