Field theoretical representation of the Hohenberg-Kohn free energy for fluids

To go beyond Gaussian approximation to the Hohenberg-Kohn free energy playi ng the key role in the density functional theory (DFT), the density functio nal integral representation would be relevant, because the held theoretic a pproach to perturbative calculations becomes available. Then we first deriv e the associated Hamiltonian of the density functional, explicitly includin g the logarithmic entropy term, from the grand partition function expressed by configurational integrals. Moreover, two things are done so that the ef ficiency of the obtained form may be revealed: we demonstrate that this rep resentation facilitates the field theoretic treatment of the perturbative c alculation and, further, compare our perturbative formulation with that of the DFT. [S1063-651X(99)51611-5].