Low temperature S-shaped heat capacities in finite nuclei

While in the thermodynamic limit a phase transition is signaled by the presence of a sharp peak in the specific heat, in finite systems a bump is usually found. However, there are relevant cases in which the presence of a low-temperature bump in the canonical specific heat of atomic nuclei is linked to the existence of isolated low energy states through a local Schottky effect, and do not represent a phase transition. Examples are presented for light and heavy deformed nuclei, by using in the calculations experimental and theoretical energy levels. (Author)