Collective coordinates, shape transitions, and shape coexistence: A microscopic approach

We investigate a description of shape mixing and shape transitions using collective coordinates. To that end we apply a theory of adiabatic large-amplitude motion to a simplified nuclear shell model, where the approximate results can be contrasted with exact diagonalizations. We find excellent agreement for different regimes, and contrast the results with those from a more standard calculation using a quadrupole constraint. We show that the method employed in this work selects diabatic (crossing) potential energy curves where these are appropriate, and discuss the implications for a microscopic study of shape coexistence.