Landau’s Theory of Phase Transitions

Abstract

Landau’s theory concerns the kind of invariants consistent with the symmetry of the crystal that may appear in the expression for the free energy. In this sense, it should be viewed as one of the successful applications of the group theory in classical physics. Unlike ordinary classical applications, however, the representation theory for space groups plays an essential role here, because a change of crystal symmetry is the main issue. It is most interesting to note that possible types of phase transitions are determined definitely solely from symmetry considerations.