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The Nambu–Jona‐Lasinio model is known for its simplicity and capacity to reproduce some of the basic characteristics of the quantum chromodynamics phase diagram. However, since it is a nonrenormalizable model, there are regularization issues that should be treated conveniently. This is the case when considering the quark anomalous magnetic moment (AMM) when external constant magnetic fields are present. Regularization procedures based on entangled functions between the magnetic field and the cutoff of the model can predict first‐order phase transitions for chiral symmetry restoration at finite values of magnetic fields and inverse magnetic catalysis. The strengths of magnetic fields explored in NJL model and lattice QCD do not show first‐order phase transition. In the present work, we show that some of the previous results are regularization‐dependent effects and how to handle the divergences using the vacuum magnetic regularization scheme. [ABSTRACT FROM AUTHOR]

We use a three-flavor Nambu–Jona-Lasinio model to study the thermodynamics of strange quark matter under a strong magnetic field. The model Lagrangian features flavor SU(3) four-quark interactions and six-quark interactions that break the U A (1) symmetry. We incorporate thermomagnetic effects in the four-quark coupling by fitting lattice results for the average of u and d quark condensates close to the pseudocritical temperature. We compute the pressure at the mean field level and obtain the magnetization of quark matter. We adopt the recently proposed vacuum magnetic regularization (VMR) scheme, in that divergent quark mass independent contributions are not subtracted, thereby avoiding unphysical results for the magnetization. We devote special attention to the renormalized magnetization, a projected quantity that allows for direct comparisons with lattice QCD simulations. Our results are in very good agreement with lattice data indicating a paramagnetic behavior for quark matter. [ABSTRACT FROM AUTHOR]

The π 0 neutral meson pole mass is calculated in a strongly magnetized medium using the SU(2) Nambu–Jona–Lasinio model within the random phase approximation (RPA) at zero temperature and zero baryonic density. We employ a magnetic field dependent coupling, G ( e B ) , fitted to reproduce lattice QCD results for the quark condensates. Divergent quantities are handled with a magnetic field independent regularization scheme in order to avoid unphysical oscillations. A comparison between the running and the fixed couplings reveals that the former produces results much closer to the predictions from recent lattice calculations. In particular, we find that the π 0 meson mass systematically decreases when the magnetic field increases while the scalar mass remains almost constant. We also investigate how the magnetic background influences other mesonic properties such as f π 0 and g π 0 q q . [ABSTRACT FROM AUTHOR]

In this work we calculate the pole-mass of the ρ 0 meson with different spin projections s z = 0 , ± 1 in the context of the magnetized two-flavor Nambu–Jona–Lasinio model. Making use of the mean field approximation to obtain the effective quark mass as a function of the magnetic field, we apply the random phase approximation (RPA) to the vector channel in order to calculate the polarization function for each spin component. We adopt the magnetic field independent regularization (MFIR) in our evaluations as a method of separating divergences and the Pauli-Villars regularization for the vacuum contributions. The ρ 0 meson mass with spin projection s z = ± 1 is always catalyzed with the magnitude of the magnetic field, showing good agreement with Lattice QCD results. The mass projection s z = 0 has a non-monotonic behavior, decreasing until the minimum at e B ≲ 0.15 GeV2, which is in contrast with available LQCD data. [ABSTRACT FROM AUTHOR]

In this article, we calculate the magnetization and other thermodynamical quantities for strongly magnetized quark matter within the Nambu-Jona-Lasinio model at zero temperature. We assume two scenarios: chemically equilibrated charge neutral matter present in the interiors of compact stars and zero-strangeness isospin-symmetric matter created in nuclear experiments. We show that the magnetization oscillates with density but in a much more smooth form than what was previously shown in the literature. As a consequence, we do not see the unphysical behavior in the pressure in the direction perpendicular to the magnetic field that was previously found. Finally, we also analyze the effects of a vector interaction on our results. [ABSTRACT FROM AUTHOR]

The pasta phases are calculated for warm stellar matter in a framework of relativistic mean-field models, including the possibility of light cluster formation. Results from three different semiclassical approaches are compared with a quantum statistical calculation. Light clusters are considered as point-like particles, and their abundances are determined from the minimization of the free energy. The couplings of the light clusters to mesons are determined from experimental chemical equilibrium constants and many-body quantum statistical calculations. The effect of these light clusters on the chemical potentials is also discussed. It is shown that, by including heavy clusters, light clusters are present up to larger nucleonic densities, although with smaller mass fractions. [ABSTRACT FROM AUTHOR]

The cell structure of clusters in the inner crust of a cold jo-equilibrium neutron star is studied within a Thomas-Fermi approach and compared with other approaches that include shell effects. Relativistic nuclear models are considered. We conclude that the symmetry energy slope L may have quite dramatic effefcts on the cell structure if it is very large or small. Rodlike and slablike pasta clusters have been obtained in all models except one with a large slope L. [ABSTRACT FROM AUTHOR]

The cell structure of β-stable clusters in the inner crust of cold and warm neutron stars is studied within the Thomas-Fermi approach by using relativistic mean-field nuclear models. The relative size of the inner crust and the pasta phase of neutron stars is calculated, and the effect of the symmetry energy slope parameter L on the profile of the neutron star crust is discussed. It is shown that, while the size of the total crust is mainly determined by the incompressibility modulus, the relative size of the inner crust depends on L. It is found that the inner crust represents a larger fraction of the total crust for smaller values of L. Finally, it is shown that, at finite temperature the pasta phase in β-equilibrium matter essentially melts above 5 to 6 MeV, and that the onset density of the rod-like and slab-like structures does not depend on the temperature. [ABSTRACT FROM AUTHOR]