Anomalous decay of pion and eta at finite density

We study the anomalous decays $\pi^0, \eta \to\gamma\gamma$ in the framework of the three--flavor Nambu--Jona-Lasinio [NJL] model, in the vacuum and in quark matter in $\beta$ --equilibrium. It is found that the behavior of the relevant observables essentially reflects a manifestation of the partial restoration of chiral symmetry, in non strange and strange sectors. The probability of such decays decreases with density, showing that anomalous mesonic interactions are significantly affected by the medium.Comment: 12 pages, 4 figures included; revised version, to be published in Phys. Lett.

Strong and Radiative Meson Decays in a Generalized Nambu--Jona-Lasinio Model

We investigate strong and radiative meson decays in a generalized Nambu--Jona-Lasinio model. The one loop order calculation provides a satisfactory agreement with the data for the mesonic spectrum and for radiative decays. Higher order effects for strong decays of $\rho$ and $K^*$ are estimated to be large. We also discuss the role of the flavour mixing determinantal interaction.Comment: 7 pages, LaTeX, 2 figs available upon request, CRN 92-4

The QCD critical end point in the SU(3) Nambu--Jona-Lasinio model

We study the chiral phase transition at finite temperature $T$ and baryonic chemical potential $\mu_B$ within the framework of the SU(3) Nambu-Jona-Lasinio (NJL) model. The QCD critical end point (CEP) and the critical line at finite $T$ and $\mu_B$ are investigated: the study of physical quantities, such as the baryon number susceptibility and the specific heat in the vicinity the CEP, will provide relevant information concerning the order of the phase transition. The class of the CEP is determined by calculating the critical exponents of those quantities.Comment: 10 pages, 4 figures; PLB versio

Warm stellar matter with deconfinement: application to compact stars

We investigate the properties of mixed stars formed by hadronic and quark matter in $\beta$-equilibrium described by appropriate equations of state (EOS) in the framework of relativistic mean-field theory. We use the non- linear Walecka model for the hadron matter and the MIT Bag and the Nambu-Jona-Lasinio models for the quark matter. The phase transition to a deconfined quark phase is investigated. In particular, we study the dependence of the onset of a mixed phase and a pure quark phase on the hyperon couplings, quark model and properties of the hadronic model. We calculate the strangeness fraction with baryonic density for the different EOS. With the NJL model the strangeness content in the mixed phase decreases. The calculations were performed for T=0 and for finite temperatures in order to describe neutron and proto-neutron stars. The star properties are discussed. Both the Bag model and the NJL model predict a mixed phase in the interior of the star. Maximum allowed masses for proto-neutron stars are larger for the NJL model ($\sim 1.9$ M$_{\bigodot}$) than for the Bag model ($\sim 1.6$ M$_{\bigodot}$).Comment: RevTeX,14 figures, accepted to publication in Physical Review

Effects of flavor asymmetric media on pion and kaon properties

We investigate the behaviour of pion and kaon properties in dense asymmetric and neutron matter in the context of a generalized three-flavor Nambu-Jona-Lasinio model, focussing mainly on Pauli blocking and Fermi sea effects. Two main features are discussed: the splitting between charged mesons and the appearance at a low density of low-lying modes which are excitations of the Fermi sea. The contribution of the low-lying modes to the satisfaction of PCAC relations becomes more and more important as the density increases.http://www.sciencedirect.com/science/article/B6TVB-3YHFB60-2W/1/6717be6abe1fb713c2b4dc48ef40e56