Thermodynamic Geometry of Nambu -- Jona Lasinio model

The formalism of Riemannian geometry is applied to study the phase transitions in Nambu -Jona Lasinio (NJL) model. Thermodynamic geometry reliably describes the phase diagram, both in the chiral limit and for finite quark masses. The comparison between the geometrical study of NJL model and of (2+1) Quantum Chromodynamics at high temperature and small baryon density shows a clear connection between chiral symmetry restoration/breaking and deconfinement/confinement regimes

Thermal Hadronization and Hawking-Unruh Radiation in QCD

We conjecture that because of color confinement, the physical vacuum forms an event horizon for quarks and gluons which can be crossed only by quantum tunneling, i.e., through the QCD counterpart of Hawking radiation by black holes. Since such radiation cannot transmit information to the outside, it must be thermal, of a temperature determined by the chromodynamic force at the confinement surface, and it must maintain color neutrality. We explore the possibility that the resulting process provides a common mechanism for thermal hadron production in high energy interactions, from $e^+e^-$ annihilation to heavy ion collisions.Comment: 29 pages, 14 figure

Renormalization group analysis of the three-dimensional Gross-Neveu model at finite temperature and density

The Renormalization Group flow equations obtained by means of a proper time regulator are used to analyze the restoration of the discrete chiral symmetry at non-zero density and temperature in the Gross-Neveu model in d=2+1 dimensions. The effects of the wave function renormalization of the auxiliary scalar field on the transition have been studied. The analysis is performed for a number of fermion flavors N_f=12 and the limit of large N_f is also considered. The results are compared with those coming from lattice simulations.Comment: Latex file, 12 pages, 2 eps figures, minor changes, added references, published versio

Hybrid neutron stars within the Nambu-Jona-Lasinio model and confinement

Recently, it has been shown that the standard Nambu-Jona-Lasinio (NJL) model is not able to reproduce the correct QCD behavior of the gap equation at large density, and therefore a different cutoff procedure at large momenta has ben proposed. We found that, even with this density dependent cutoff procedure, the pure quark phase in neutron stars (NS) interiors is unstable, and we argue that this could be related to the lack of confinement in the original NJL model.Comment: 2 pages, 1 figure, to be published in the proceedings of the conference EXOCT07, Catania, 11-15 June, 200