Random-phase approximation approach to rotational symmetry restoration in a three-level Lipkin model
Random-phase approximation approach to rotational symmetry restoration in a three-level Lipkin model
We study an extended Lipkin-Meshkov-Glick model that permits a transition to a deformed phase with a broken continuous symmetry. Unlike simpler models, one sees a persistent zero-frequency Goldstone mode past the transition point into the deformed phase. We found that the RPA formula for the correlation energy provides a useful …