2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/18815A simple analytical microscopic expression for the surface tension of liquids $γ$ is obtained which is in a good agreement with available data of numerical experiments. We apply the integral transformation that maps the fluid Hamiltonian onto the field-theoretical Hamiltonian and show that the order parameter of the effective Hamiltonian corresponds to the one-body potential in the fluid. Revealing the physical meaning of the order parameter allows calculation of $γ$.4 pages, 1 figureSoft Condensed MatterStatistical Mechanicstext