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We use the three-flavor Nambu-Jona-Lasinio model, which includes strangeness and quark physical masses in the mean field approximation, to investigate the influence of strong magnetic fields on the QCD phase diagram covering the whole T-&mgr; plane. It is found that the first order segment of the transition line becomes longer as the field strength increases so that a larger coexistence region for hadronic and quark matter should be expected for strong magnetic fields. The location of the critical end point is also affected by the presence of magnetic fields that invariably increase the temperature value at which the first order line terminates. On the other hand, at low temperatures, the critical chemical potential displays an oscillation around the B = 0 value for magnetic fields within the 1017 - 1020 G range. These findings may have nontrivial consequences for the physics of magnetars and heavy ion collisions. [ABSTRACT FROM AUTHOR]

We calculate the pole masses of pseudoscalar mesons in a strongly magnetized medium within the framework of the SU(3) Nambu-Jona-Lasinio model, using a magnetic field-independent regularization scheme. We employ both a constant and a magnetic field-dependent coupling G(B), the latter being fitted to reproduce lattice QCD results for the pseudocritical chiral transition temperature. Numerical results for the pole masses are obtained for definite parametrizations of the model. For neutral mesons, the use of G(B) provides closer agreement with lattice QCD results, which reveal a decrease of the mass with the external field. On the contrary, charged mesons masses are enhanced by B, showing no sign of the nonmonotonous behavior found in recent lattice QCD simulations. [ABSTRACT FROM AUTHOR]

Extending our recently published SU(2) results for zero temperature, we now compute the QCD equation of state for finite isospin density within the three-flavor Nambu-Jona-Lasinio (NJL) model in the mean field approximation, motivated by the recently obtained lattice QCD results for both zero and finite temperatures. Like our previous study, here also we have considered both the commonly used traditional cutoff regularization scheme and the medium separation scheme. Our results are compared with recent high-precision lattice simulations as well as previously obtained results in two-flavor Nambu-Jona-Lasinio model. The agreement between the lattice results and the predictions from three-flavor NJL model is very good for low values of µI (for both zero and finite temperatures). For larger values of µI, the agreement between lattice data and the two-flavor NJL predictions is surprisingly good and better than with the three-flavor predictions. [ABSTRACT FROM AUTHOR]

The importance of implementing a proper regularization procedure in order to treat thermo and magnetic contributions within nonrenormalizable theories is investigated. Our study suggests that potential divergences should be isolated into the vacuum and purely magnetic contributions and then regularized while the convergent thermomagnetic contributions should be integrated over the full momentum range. This prescription is illustrated by applying the proper time formalism to the two flavor Polyakov-Nambu-Jona-Lasinio model, whose magnetic field-dependent coupling has been recently determined. Observables such as the pressure, magnetization, speed of sound squared, and specific heat evaluated within our scheme are compared with results furnished by other three possible prescriptions. We show that these quantities display a thermomagnetic behavior which is physically more consistent when our scheme is adopted. In particular, we demonstrate that naively regulating the (entangled) vacuum, magnetic, and thermomagnetic contributions leads to physically inconsistent results especially at the high temperature domain. [ABSTRACT FROM AUTHOR]

We compute the QCD equation of state for zero temperature and finite isospin density within the Nambu-Jona-Lasinio model in the mean field approximation, motivated by the recently obtained lattice QCD results for a new class of compact stars: pion stars. We have considered both the commonly used traditional cutoff regularization scheme and the medium separation scheme, where in the latter purely vacuum contributions are separated in such a way that one is left with ultraviolet divergent momentum integrals depending only on vacuum quantities. We have also compared our results with the recent results from lattice QCD and chiral perturbation theory. [ABSTRACT FROM AUTHOR]

We study the regularization dependence of the Nambu-Jona-Lasinio model (NJL) predictions for some properties of magnetized quark matter at zero temperature (and baryonic density) in the mean field approximation. The model parameter dependence for each regularization procedure is also analyzed in detail. We calculate the average and difference of the quark condensates using different regularization methods and compare with recent lattice results. In this context, the reliability of the different regularization procedures is discussed. [ABSTRACT FROM AUTHOR]

A magnetic field independent regularization scheme (zMFIR) based on the Hurwitz-Riemann zeta function is introduced. The new technique is applied to the regularization of the mean-field thermodynamic potential and mass gap equation within the SU(2) Nambu-Jona-Lasinio model in a hot and magnetized medium. The equivalence of the new and the standard MFIR scheme is demonstrated. The neutral meson pole mass is calculated in a hot and magnetized medium and the advantages of using the new regularization scheme are shown. [ABSTRACT FROM AUTHOR]

In this work we study the electrized quark matter under finite temperature and density conditions in the context of the SU(2) and SU(3) Nambu-Jona-Lasinio models. To this end, we evaluate the effective quark masses and the Schwinger quark-antiquark pair production rate. For the SU(3) NJL model we incorporate in the Lagrangian the 't Hooft determinant and we present a set of analytical expressions more convenient for numerical evaluations. We predict a decrease of the pseudocritical electric field with the increase of the temperature for both models and a more prominent production rate for the SU(3) model when compared to the SU(2). [ABSTRACT FROM AUTHOR]

The deconfinement and chiral phase transitions are studied in the context of the electrized quark matter at finite temperature in the two-flavor Polyakov-Nambu-Jona-Lasinio model. Using the mean field approximation and an electric field independent regularization we show that the effect of temperature and/or electric fields is to partially restore the chiral symmetry. The deconfinement phase transition is slightly affected by the magnitude of the electric field. To this end we show how the effective quark masses and the expectation value of the Polyakov loop are affected by the electric fields at finite temperatures. As a very interesting result, the pseudocritical temperatures for chiral symmetry restoration and deconfinement decrease as we increase the magnitude of the electric fields; however, both start to increase after some critical value of the electric field. [ABSTRACT FROM AUTHOR]