Improved analysis of the Landau theory of the uniaxial-biaxial nematic phase transition

A phenomenological theory is developed for uniaxial and biaxial nematic phases, based on a two component tensor order parameter. Phase diagrams are plotted and investigated in the plane of two thermodynamic parameters. Anomalies in thermal properties are studied in the vicinity of an isolated four-phase critical point. The temperature dependences of the order parameter and the thermodynamic quantities are also calculated theoretically for the first time.