Theory of phase transitions in binary mixtures

A microscopic approach for the description of critical phenomena in mixtures is presented. Near the critical point, the theory develops a renormalization group structure which allows for the identification of several possible critical behaviours corresponding to different fixed points. For a generic neutral binary mixture, the most stable fixed point gives rise to the same critical exponents as predicted by the well known phenomenological approach, providing a microscopic mechanism for such a behaviour. The order parameter psi is identified and two exact relations expressing psi in terms of experimentally accessible quantities are given. As an example, some results for the neon-krypton mixture are presented.