Specific Heat of Strongly Interacting Matter

Abstract

Strong analogies exist between the spectra of baryons and nuclei. Aside from the difference in scale, in both cases the low--lying spectrum is collective and therefore sparse and increases exponentially with increasing exicitation energy. In the case of deformed nuclei this change in level density gives rise to a peak in the specific heat which has been associated with the shape transitions in the nucleus found in mean field calculations [1]. These “phase” transitions are associated with the change from a low--lying collective spectrum to a denser more random spectrum due to the independent particle degrees of freedom at higher excitation energies. One observes a similar change in level density in the hadron spectrum [2] -- namely low--lying sparse baryon resonances which lie on (almost) linear trajectories [3,4] corresponding to the collective rotational bands in the nuclear case which are built on a few low--lying band heads. The origin of the change in the level density in the hadron case requires a reliable QCD description of the hadrons, which is not unfortunately not available at present.