Evidence for phase transitions in finite systems

A canonical-ensemble calculation of the specific heat in ${}_{}{}^{20}{}_{}{}^{}\mathrm{Ne}$ using the eigenstates of a number of realistic interactions and the energies of the states obtained experimentally exhibits a prominent peak at T≃1.7–2.5 MeV which is associated with the deformed-to-spherical phase transition seen in finite-temperature mean-field calculations. This phase transition arises from a change in the relevant degrees of freedom describing the system and will occur for any nucleus which has a low-lying collective spectrum. Including a continuum in addition to the discrete spectrum does not produce an additional peak in the specific heat at low temperatures.