Journal of Physics A. Mathematical and General vol:24 issue:19 pages:4495-4509
Different expressions for calculating the Berry phase of adiabatic processes are reviewed and their limitations are discussed. These expressions are then applied to the case of a circuit surrounding a triple degeneracy. It is shown that the most general formula for the Berry phase requires the use of the full SU(3) invariance group of a T state coupled to epsilon + tau-1 + tau-2 modes. The T x (epsilon + tau-2) Jahn-Teller problem appears as a special case with SO(3) symmetry.