Meson properties at finite temperature in a three flavor nonlocal chiral quark model with Polyakov loop

We study the finite temperature behavior of light scalar and pseudoscalar meson properties in the context of a three-flavor nonlocal chiral quark model. The model includes mixing with active strangeness degrees of freedom, and takes care of the effect of gauge interactions by coupling the quarks with the Polyakov loop. We analyze the chiral restoration and deconfinement transitions, as well as the temperature dependence of meson masses, mixing angles and decay constants. The critical temperature is found to be T_c = 202 MeV, in better agreement with lattice results than the value recently obtained in the local SU(3) PNJL model. It is seen that above T_c pseudoscalar meson masses get increased, becoming degenerate with the masses of their chiral partners. The temperatures at which this matching occurs depend on the strange quark composition of the corresponding mesons. The topological susceptibility shows a sharp decrease after the chiral transition, signalling the vanishing of the U(1)_A anomaly for large temperatures.Comment: 21 pages, 4 figures. Fig. 3 and final part of Sect. IV modified, references added, conclusions unchanged. To be published in Phys. Rev.

Radiative decays of mesons in the NJL model

We revisit the theoretical predictions for anomalous radiative decays of pseudoscalar and vector mesons. Our analysis is performed in the framework of the Nambu-Jona-Lasinio model, introducing adequate parameters to account for the breakdown of chiral symmetry. The results are comparable with those obtained in previous approaches.Comment: 19 pages incl. 4 figure

Electric polarizability of nuclei from a longitudinal sum rule

The nuclear electric polarizability is theoretically analyzed using a sum rule derived from the longitudinal part of the forward Compton amplitude. Beyond the leading dipole contribution, this approach leads to the presence of potential-dependent terms that do not show up in previous analyses. The significance of these new contributions is illustrated by performing an explicit calculation for a proton-neutron system interacting via a separable potential.Comment: 9 pages, revtex. Minor changes, two references added. To appear in Nucl. Phys.

Form factors of radiative pion decays in nonlocal chiral quark models

We study the radiative pion decay pi+ -> e+ nu_e gamma within nonlocal chiral quark models that include wave function renormalization. In this framework we analyze the momentum dependence of the vector form factor F_V(q^2), and the slope of the axial-vector form factor F_A(q^2) at threshold. Our results are compared with available experimental information and with the predictions given by the NJL model. In addition we calculate the low energy constants l_5 and l_6, comparing our results with the values obtained in chiral perturbation theory.Comment: 22 pages, 1 figure. arXiv admin note: substantial text overlap with arXiv:1011.640

Phase diagram of neutron star quark matter in nonlocal chiral models

We analyze the phase diagram of two-flavor quark matter under neutron star constraints for a nonlocal covariant quark model within the mean field approximation. Applications to cold compact stars are discussed.Comment: 3 pages, 1 figure, proceedings of the IV International Conference on Quarks and Nuclear Physics (QNP06), Madrid, Spain, June 5-10, 2006. To appear in Eur. Phys. J.

Characteristics of the chiral phase transition in nonlocal quark models

The characteristics of the chiral phase transition are analyzed within the framework of chiral quark models with nonlocal interactions in the mean field approximation. In the chiral limit, we develop a semi-analytic framework which allows us to explicitly determine the phase transition curve, the position of the critical points, some relevant critical exponents, etc. For the case of finite current quark masses, we show the behavior of various thermodynamical and chiral response functions across the phase transition.Comment: 19 pages, 5 figures. Figures 1 and 2 modified, references added, minor changes in the presentation and in the discussion of results. Accepted for publication in Phys. Rev.

Color neutrality effects in the phase diagram of the PNJL model

The phase diagram of a two-flavor Polyakov loop Nambu-Jona-Lasinio model is analyzed imposing the constraint of color charge neutrality. Main effects of this constraint are a shrinking of the chiral symmetry breaking (chiSB) domain in the T-mu plane, a shift of the critical point to lower temperatures and a coexistence of chiSB and two-flavor superconducting phases. The effects can be understood in view of the presence of a nonvanishing color chemical potential mu_8, which is necessary to compensate the color charge density rho_8 induced by the nonvanishing Polyakov-loop mean field phi_3.Comment: 8 pages, 4 figures, figures added, minor text modification