Progress of Theoretical Physics
Landau Theory and the Inverse Temperature Series Expansion in the Method of Symmetry Breaking Potential
M. Yamashita
Abstract
The Landau theory on the phase transition derived statistical-mechanically on the basis of the symmetry breaking potential method with the use of inverse temperature series expansion is examined. In that method an estimate of the mean field is improved systematically by taking account of short range correlations. The results at low temperatures in relation to the expansion parameter are investigated. The critical temperature obtained is equal to that in the [n, 0] Padé approximation applied to the inverse of susceptibility. By making use of many results obtained up to now in the calculation of susceptibility with the use of inverse temperature series expansion, the critical temperatures of the Ising, Heisenberg and XY models are determined. The possibility of long range ordering in low dimensional systems and the case of the symmetry breaking potential incommutative with the Hamiltonian are also investigated.