The effect of the density dependence of the nucleonic equation of state and the hyperon meson cou... more The effect of the density dependence of the nucleonic equation of state and the hyperon meson couplings on the star properties, including strangeness content, mass and radius, are studied within a relativistic mean field formalism. It is shown that there is still lacking information on the nucleonic equation of state at supra-saturation densities and on the hyperon interactions in nuclear matter that will allow a clear answer to the question whether the mass of the pulsar J1614-2230 could rule out exotic degrees of freedom from the interior of compact stars. We show that some star properties are affected in a similar way by the density dependence of the symmetry energy and the hyperon content of the star. To disentangle these two effects it is essential to have a good knowledge of the equation of state at supra-saturation densities. A linear correlation between the radius and the strangeness content of a star with a fixed mass is obtained.
The chiral model is used to describe quark matter under strong magnetic fields and compared to ot... more The chiral model is used to describe quark matter under strong magnetic fields and compared to other models, the MIT bag model and the two flavors Nambu-Jona-Lasinio model. The effect of vacuum corrections due to the magnetic field is discussed. It is shown that if the magnetic field vacuum corrections are not taken into account explicitly the parameters of the models should be fitted to low density meson properties in the presence of the magnetic field.
The effect of the density dependence of the nucleonic equation of state and the hyperon meson cou... more The effect of the density dependence of the nucleonic equation of state and the hyperon meson couplings on the star properties, including strangeness content, mass and radius, are studied within a relativistic mean field formalism. It is shown that there is still lacking information on the nucleonic equation of state at supra-saturation densities and on the hyperon interactions in nuclear matter that will allow a clear answer to the question whether the mass of the pulsar J1614-2230 could rule out exotic degrees of freedom from the interior of compact stars. We show that some star properties are affected in a similar way by the density dependence of the symmetry energy and the hyperon content of the star. To disentangle these two effects it is essential to have a good knowledge of the equation of state at supra-saturation densities. A linear correlation between the radius and the strangeness content of a star with a fixed mass is obtained.
The joint effect of the density dependence of the symmetry energy and strangeness content on the ... more The joint effect of the density dependence of the symmetry energy and strangeness content on the structure of cold neutron stars is studied within the framework of a relativistic mean field theory. It is shown that 2$M_\odot$ are obtained for repulsive $YY$ interaction and preferably for a small or a large slope $L$. An attractive $\Sigma$ potential in nuclear matter will favor the appearance of strangeness in stars with a mass as small as $\sim 1 M_\odot$, if, however it is repulsive only stars with a mass $\gtrsim 1.4 M_\odot$ will contain strangeness. The joint effect of reducing the symmetry energy slope and including hyperons is to farther reduce the radius. Neutron star maximum mass evolve non-monotonically with the symmetry energy slope, and the smallest masses are obtained for values $L\sim 80$ MeV. Other neutron star variables evolve nonlinearly with the slope of the symmetry energy and depend on the hyperon-nucleon and hyperon-hyperon couplings. The radius of a neutron sta...
A quark-meson coupling model based on the quark model proposed by Bogoliubov for the description ... more A quark-meson coupling model based on the quark model proposed by Bogoliubov for the description of the quark dynamics is developed and applied to the description of neutron stars. Starting from a SU(3) symmetry approach, it is shown that this symmetry has to be broken in order to satisfy the constraints set by the hypernuclei and by neutron stars. The model is able to describe observations such as two-solar-mass stars or the radius of canonical neutron stars within the uncertainties presently accepted. If the optical potentials for and hyperons in symmetric nuclear matter at saturation obtained from laboratory measurements of hypernuclei properties are imposed, the model predicts no strangeness inside neutron stars.
The neutron-proton-electron(npe) matter under a strong magnetic field is studied in the context o... more The neutron-proton-electron(npe) matter under a strong magnetic field is studied in the context of the covariant Vlasov approach. We use a Walecka-type hadronic model and the dispersion relations for the longitudinal and transverse modes are obtained. The instability regions for longitudinal and transverse modes are also studied. The crust-core transition of a magnetized neutron star is discussed.
In the present study we analyse the effect of the density dependence of the symmetry energy on th... more In the present study we analyse the effect of the density dependence of the symmetry energy on the hyperonic content of neutron stars within a relativistic mean field description of stellar matter. For the Λ-hyperon, we consider parametrizations calibrated to Λ-hypernuclei. For the Σ and Ξ-hyperons uncertainties that reflect the present lack of experimental information on Σ and Ξ-hypernuclei are taken into account. We perform our study considering nuclear equations of state that predict two solar mass stars, and satisfy other well settled nuclear matter properties. The effect of the presence of hyperons on the radius, the direct Urca processes, and the cooling of accreting neutron stars are discussed. We show that some star properties are affected in a similar way by the density dependence of the symmetry energy and the hyperon content of the star. To disentangle these two effects it is essential to have a good knowledge of the equation of state at supra-saturation densities. The density dependence of the symmetry energy affects the order of appearance of the different hyperons, which may have direct implications on the neutron star cooling as different hyperonic neutrino processes processes may operate at the center of massive stars. For models which allow for the direct Urca process to operate, hyperonic and purely nucleonic ones are shown to have a similar luminosity when hyperons are included in agreement with modern experimental data. It is shown that for a density dependent hadronic model constrained by experimental, theoretical and observational data, the low-luminosity of SAX J1808.4 − 3658 can only be modelled for a hyperonic NS, suggesting that hyperons could be present in its core.
The Self-consistent random phase approximation (SCRPA) is applied to the exactly solvable model w... more The Self-consistent random phase approximation (SCRPA) is applied to the exactly solvable model with fermion boson coupling proposed by Schütte and Da-Providencia. Very encouraging results in comparison with the exact solution of the model for various observables are obtained. The transition from the normal phase to the phase with a spontaneously broken symmetry is carefully investigated. The strong reduction of the variance in SCRPA vs HF is pointed out.
ABSTRACT L'approximation de la phase aléatoire auto-cohérente (SCRPA) est une méthode qui... more ABSTRACT L'approximation de la phase aléatoire auto-cohérente (SCRPA) est une méthode qui permet d'inclure dans la théorie de champ moyen des corrélations dans l'état fondamental et les états excités. Elle constitue alors une méthode de type champ moyen pour les fluctuations quantiques. Elle a l'avantage de ne pas violer le principe de Pauli, contrairement à la RPA standard. qui, elle, est basée sur l'approximation dite de quasi-bosons. De plus, la SCRPA peut être formulée à partir d'un principe variationnel. Nous présentons la méthode SCRPA pour la description de la superfluidité dans les systèmes de fermions en utilisant sa version Quasi-particule (SCQRPA). Une étude détaillée de la transition de phase normale/superfluide ainsi que une discussion du mode mou qui enclenche la brisure de symétrie nombre de particules sont présentées. Comme application, nous avons traité le modèle d'appariement à deux niveaux qui est un modèle exactement soluble. Des bons résultats sont obtenus en comparaison avec les résultats exacts. La nature du mode spurieux dans la SCQRPA est identifiée. Une forte réduction de la fluctuation du nombre total de particules dans la SCQRPA par rapport à la méthode BCS est établie. La transition de la phase superfluide à la phase normale est soigneusement étudiée. Une nouvelle méthode de calcul des nombres d'occupation est présentée. Le succès de la méthode SCQRPA est aussi présent dans le cas d'un modèle mélangeant fermions en bosons tel que le modèle de Da-Providencia-Schütte. Il subsiste cependant un problème concernant le mode spurieux qui doit être encore approfondi. Dans le cas du modèle de la séniorité, on montre que la méthode SCQRPA permet d'une manière naturelle de restaurer la symétrie (nombre de particules) brisée au niveau de l'approximation de champ moyen. Ceci est réalisé par l'introduction d'un second paramètre de Lagrange qui fixe la variance de l'opérateur de symétrie à zéro. Cette caractéristique importante de la méthode SCQRPA est signalée pour la première fois.
We study the effect of a strong magnetic field on the proton and neutron spin polarization and ma... more We study the effect of a strong magnetic field on the proton and neutron spin polarization and magnetic susceptibility of asymmetric nuclear matter within a relativistic mean-field approach. It is shown that magnetic fields B ∼ 10 16-10 17 G have already noticeable effects on the range of densities of interest for the study of the crust of a neutron star. Although the proton susceptibility is larger for weaker fields, the neutron susceptibility becomes of the same order or even larger for small proton fractions and subsaturation densities for B > 10 16 G. We expect that neutron superfluidity in the crust will be affected by the presence of magnetic fields.
The joint effect of the density dependence of the symmetry energy and strangeness content on the ... more The joint effect of the density dependence of the symmetry energy and strangeness content on the structure of cold neutron stars is studied within the framework of a relativistic mean field theory. It is shown that 2M⊙ are obtained for repulsive Y Y interaction and preferably for a small or a large slope L. An attractive Σ potential in nuclear matter will favor the appearance of strangeness in stars with a mass as small as ∼ 1M⊙, if, however it is repulsive only stars with a mass 1.4M⊙ will contain strangeness. The joint effect of reducing the symmetry energy slope and including hyperons is to farther reduce the radius. Neutron star maximum mass evolve non-monotonically with the symmetry energy slope, and the smallest masses are obtained for values L ∼ 80 MeV. Other neutron star variables evolve nonlinearly with the slope of the symmetry energy and depend on the hyperon-nucleon and hyperon-hyperon couplings. The radius of a neutron star is linearly correlated with the neutron star t...
We study the influence of the isovector-scalar meson on the spinodal instabilities and the distil... more We study the influence of the isovector-scalar meson on the spinodal instabilities and the distillation effect in asymmetric non-homogenous nuclear matter under strong magnetic fields, of the order of 10 18 − 10 19 G. Relativistic nuclear models both with constant couplings (NLW) and with density dependent parameters (DDRH) are considered. A strong magnetic field can have large effects on the instability regions giving rise to bands of instability and wider unstable regions. It is shown that for neutron rich matter the inclusion of the δ meson increases the size of the instability region for NLW models and decreases it for the DDRH models. The effect of the δ meson on the transition density to homogeneous β-equilibrium matter is discussed. The DDRHδ model predicts the smallest transition pressures, about half the values obtained for NLδ.
The effect of the density dependence of the nucleonic equation of state and the hyperon meson cou... more The effect of the density dependence of the nucleonic equation of state and the hyperon meson couplings on the star properties, including strangeness content, mass and radius, are studied within a relativistic mean field formalism. It is shown that there is still lacking information on the nucleonic equation of state at supra-saturation densities and on the hyperon interactions in nuclear matter that will allow a clear answer to the question whether the mass of the pulsar J1614-2230 could rule out exotic degrees of freedom from the interior of compact stars. We show that some star properties are affected in a similar way by the density dependence of the symmetry energy and the hyperon content of the star. To disentangle these two effects it is essential to have a good knowledge of the equation of state at supra-saturation densities. A linear correlation between the radius and the strangeness content of a star with a fixed mass is obtained.
The Landau Fermi Liquid parameters are calculated for charge neutral asymmetric nuclear matter in... more The Landau Fermi Liquid parameters are calculated for charge neutral asymmetric nuclear matter in beta equilibrium at zero temperature in the presence of a very strong magnetic field with relativistic mean-field models. Due to the isospin structure of the system, with different populations of protons and neutrons and spin alignment to the field, we find nonvanishing Landau mixing parameters. The existence of quantized Landau levels for the charged sector has some impact on the Landau parameters with the presence of discretized features in those involving the proton sector. Using the Fermi liquid formalism singlet and triplet excited quasiparticle states are analyzed, and we find that in-medium effects and magnetic fields are competing, however, the former are more important in the interaction energy range considered. It is found that for magnetic field strengths Log 10 B (G) ≤ 17 the relative low polarization of the system produces mild changes in the generalized Landau parameters with respect to the unmagnetized case, while for larger strengths there is a resolution of the degeneracy of the interaction energies of quasiparticles in the system.
The Self-consistent random phase approximation (SCRPA) is applied to the exactly solvable model w... more The Self-consistent random phase approximation (SCRPA) is applied to the exactly solvable model with fermion boson coupling proposed by Schütte and Da-Providencia. Very encouraging results in comparison with the exact solution of the model for various observables are obtained. The transition from the normal phase to the phase with a spontaneously broken symmetry is carefully investigated. The strong reduction of the variance in SCRPA vs HF is pointed out.
We study the effect of strong magnetic fields, of the order of 10 18 − 10 19 G, on the instabilit... more We study the effect of strong magnetic fields, of the order of 10 18 − 10 19 G, on the instability region of nuclear matter at subsaturation densities. Relativistic nuclear models both with constant couplings and with density dependent parameters are considered. It is shown that a strong magnetic field can have large effects on the instability regions giving rise to bands of instability and wider unstable regions. As a consequence we predict larger transition densities at the inner edge of the crust of compact stars with strong magnetic field. The direction of instability gives rise to a very strong distillation effect if the last Landau level is only partially filled. However, for almost completed Landau levels an anti-distillation effect may occur.
We investigate the effects of strong magnetic fields on the equation of state of warm stellar mat... more We investigate the effects of strong magnetic fields on the equation of state of warm stellar matter as it may occur in a protoneutron star. Both neutrino free and neutrino trapped matter at a fixed entropy per baryon are analyzed. A relativistic meanfield nuclear model, including the possibility of hyperon formation, is considered. A density dependent magnetic field with the magnitude 10 15 G at the surface and not more than 3 × 10 18 G at the center is considered. The magnetic field gives rise to a neutrino suppression, mainly at low densities, in matter with trapped neutrinos. It is shown that an hybrid protoneutron star will not evolve to a low mass blackhole if the magnetic field is strong enough and the magnetic field does not decay. However, the decay of the magnetic field after cooling may give rise to the formation of a low mass blackhole.
The chiral model is used to describe quark matter under strong magnetic fields and compared to ot... more The chiral model is used to describe quark matter under strong magnetic fields and compared to other models, the MIT bag model and the two flavor Nambu-Jona-Lasinio model. The effect of vacuum corrections due to the magnetic field is discussed. It is shown that if the magnetic field vacuum corrections are not taken into account explicitly the parameters of the models should be fitted to low density meson properties in the presence of the magnetic field.
The effect of the density dependence of the nucleonic equation of state and the hyperon meson cou... more The effect of the density dependence of the nucleonic equation of state and the hyperon meson couplings on the star properties, including strangeness content, mass and radius, are studied within a relativistic mean field formalism. It is shown that there is still lacking information on the nucleonic equation of state at supra-saturation densities and on the hyperon interactions in nuclear matter that will allow a clear answer to the question whether the mass of the pulsar J1614-2230 could rule out exotic degrees of freedom from the interior of compact stars. We show that some star properties are affected in a similar way by the density dependence of the symmetry energy and the hyperon content of the star. To disentangle these two effects it is essential to have a good knowledge of the equation of state at supra-saturation densities. A linear correlation between the radius and the strangeness content of a star with a fixed mass is obtained.
The chiral model is used to describe quark matter under strong magnetic fields and compared to ot... more The chiral model is used to describe quark matter under strong magnetic fields and compared to other models, the MIT bag model and the two flavors Nambu-Jona-Lasinio model. The effect of vacuum corrections due to the magnetic field is discussed. It is shown that if the magnetic field vacuum corrections are not taken into account explicitly the parameters of the models should be fitted to low density meson properties in the presence of the magnetic field.
The effect of the density dependence of the nucleonic equation of state and the hyperon meson cou... more The effect of the density dependence of the nucleonic equation of state and the hyperon meson couplings on the star properties, including strangeness content, mass and radius, are studied within a relativistic mean field formalism. It is shown that there is still lacking information on the nucleonic equation of state at supra-saturation densities and on the hyperon interactions in nuclear matter that will allow a clear answer to the question whether the mass of the pulsar J1614-2230 could rule out exotic degrees of freedom from the interior of compact stars. We show that some star properties are affected in a similar way by the density dependence of the symmetry energy and the hyperon content of the star. To disentangle these two effects it is essential to have a good knowledge of the equation of state at supra-saturation densities. A linear correlation between the radius and the strangeness content of a star with a fixed mass is obtained.
The joint effect of the density dependence of the symmetry energy and strangeness content on the ... more The joint effect of the density dependence of the symmetry energy and strangeness content on the structure of cold neutron stars is studied within the framework of a relativistic mean field theory. It is shown that 2$M_\odot$ are obtained for repulsive $YY$ interaction and preferably for a small or a large slope $L$. An attractive $\Sigma$ potential in nuclear matter will favor the appearance of strangeness in stars with a mass as small as $\sim 1 M_\odot$, if, however it is repulsive only stars with a mass $\gtrsim 1.4 M_\odot$ will contain strangeness. The joint effect of reducing the symmetry energy slope and including hyperons is to farther reduce the radius. Neutron star maximum mass evolve non-monotonically with the symmetry energy slope, and the smallest masses are obtained for values $L\sim 80$ MeV. Other neutron star variables evolve nonlinearly with the slope of the symmetry energy and depend on the hyperon-nucleon and hyperon-hyperon couplings. The radius of a neutron sta...
A quark-meson coupling model based on the quark model proposed by Bogoliubov for the description ... more A quark-meson coupling model based on the quark model proposed by Bogoliubov for the description of the quark dynamics is developed and applied to the description of neutron stars. Starting from a SU(3) symmetry approach, it is shown that this symmetry has to be broken in order to satisfy the constraints set by the hypernuclei and by neutron stars. The model is able to describe observations such as two-solar-mass stars or the radius of canonical neutron stars within the uncertainties presently accepted. If the optical potentials for and hyperons in symmetric nuclear matter at saturation obtained from laboratory measurements of hypernuclei properties are imposed, the model predicts no strangeness inside neutron stars.
The neutron-proton-electron(npe) matter under a strong magnetic field is studied in the context o... more The neutron-proton-electron(npe) matter under a strong magnetic field is studied in the context of the covariant Vlasov approach. We use a Walecka-type hadronic model and the dispersion relations for the longitudinal and transverse modes are obtained. The instability regions for longitudinal and transverse modes are also studied. The crust-core transition of a magnetized neutron star is discussed.
In the present study we analyse the effect of the density dependence of the symmetry energy on th... more In the present study we analyse the effect of the density dependence of the symmetry energy on the hyperonic content of neutron stars within a relativistic mean field description of stellar matter. For the Λ-hyperon, we consider parametrizations calibrated to Λ-hypernuclei. For the Σ and Ξ-hyperons uncertainties that reflect the present lack of experimental information on Σ and Ξ-hypernuclei are taken into account. We perform our study considering nuclear equations of state that predict two solar mass stars, and satisfy other well settled nuclear matter properties. The effect of the presence of hyperons on the radius, the direct Urca processes, and the cooling of accreting neutron stars are discussed. We show that some star properties are affected in a similar way by the density dependence of the symmetry energy and the hyperon content of the star. To disentangle these two effects it is essential to have a good knowledge of the equation of state at supra-saturation densities. The density dependence of the symmetry energy affects the order of appearance of the different hyperons, which may have direct implications on the neutron star cooling as different hyperonic neutrino processes processes may operate at the center of massive stars. For models which allow for the direct Urca process to operate, hyperonic and purely nucleonic ones are shown to have a similar luminosity when hyperons are included in agreement with modern experimental data. It is shown that for a density dependent hadronic model constrained by experimental, theoretical and observational data, the low-luminosity of SAX J1808.4 − 3658 can only be modelled for a hyperonic NS, suggesting that hyperons could be present in its core.
The Self-consistent random phase approximation (SCRPA) is applied to the exactly solvable model w... more The Self-consistent random phase approximation (SCRPA) is applied to the exactly solvable model with fermion boson coupling proposed by Schütte and Da-Providencia. Very encouraging results in comparison with the exact solution of the model for various observables are obtained. The transition from the normal phase to the phase with a spontaneously broken symmetry is carefully investigated. The strong reduction of the variance in SCRPA vs HF is pointed out.
ABSTRACT L'approximation de la phase aléatoire auto-cohérente (SCRPA) est une méthode qui... more ABSTRACT L'approximation de la phase aléatoire auto-cohérente (SCRPA) est une méthode qui permet d'inclure dans la théorie de champ moyen des corrélations dans l'état fondamental et les états excités. Elle constitue alors une méthode de type champ moyen pour les fluctuations quantiques. Elle a l'avantage de ne pas violer le principe de Pauli, contrairement à la RPA standard. qui, elle, est basée sur l'approximation dite de quasi-bosons. De plus, la SCRPA peut être formulée à partir d'un principe variationnel. Nous présentons la méthode SCRPA pour la description de la superfluidité dans les systèmes de fermions en utilisant sa version Quasi-particule (SCQRPA). Une étude détaillée de la transition de phase normale/superfluide ainsi que une discussion du mode mou qui enclenche la brisure de symétrie nombre de particules sont présentées. Comme application, nous avons traité le modèle d'appariement à deux niveaux qui est un modèle exactement soluble. Des bons résultats sont obtenus en comparaison avec les résultats exacts. La nature du mode spurieux dans la SCQRPA est identifiée. Une forte réduction de la fluctuation du nombre total de particules dans la SCQRPA par rapport à la méthode BCS est établie. La transition de la phase superfluide à la phase normale est soigneusement étudiée. Une nouvelle méthode de calcul des nombres d'occupation est présentée. Le succès de la méthode SCQRPA est aussi présent dans le cas d'un modèle mélangeant fermions en bosons tel que le modèle de Da-Providencia-Schütte. Il subsiste cependant un problème concernant le mode spurieux qui doit être encore approfondi. Dans le cas du modèle de la séniorité, on montre que la méthode SCQRPA permet d'une manière naturelle de restaurer la symétrie (nombre de particules) brisée au niveau de l'approximation de champ moyen. Ceci est réalisé par l'introduction d'un second paramètre de Lagrange qui fixe la variance de l'opérateur de symétrie à zéro. Cette caractéristique importante de la méthode SCQRPA est signalée pour la première fois.
We study the effect of a strong magnetic field on the proton and neutron spin polarization and ma... more We study the effect of a strong magnetic field on the proton and neutron spin polarization and magnetic susceptibility of asymmetric nuclear matter within a relativistic mean-field approach. It is shown that magnetic fields B ∼ 10 16-10 17 G have already noticeable effects on the range of densities of interest for the study of the crust of a neutron star. Although the proton susceptibility is larger for weaker fields, the neutron susceptibility becomes of the same order or even larger for small proton fractions and subsaturation densities for B > 10 16 G. We expect that neutron superfluidity in the crust will be affected by the presence of magnetic fields.
The joint effect of the density dependence of the symmetry energy and strangeness content on the ... more The joint effect of the density dependence of the symmetry energy and strangeness content on the structure of cold neutron stars is studied within the framework of a relativistic mean field theory. It is shown that 2M⊙ are obtained for repulsive Y Y interaction and preferably for a small or a large slope L. An attractive Σ potential in nuclear matter will favor the appearance of strangeness in stars with a mass as small as ∼ 1M⊙, if, however it is repulsive only stars with a mass 1.4M⊙ will contain strangeness. The joint effect of reducing the symmetry energy slope and including hyperons is to farther reduce the radius. Neutron star maximum mass evolve non-monotonically with the symmetry energy slope, and the smallest masses are obtained for values L ∼ 80 MeV. Other neutron star variables evolve nonlinearly with the slope of the symmetry energy and depend on the hyperon-nucleon and hyperon-hyperon couplings. The radius of a neutron star is linearly correlated with the neutron star t...
We study the influence of the isovector-scalar meson on the spinodal instabilities and the distil... more We study the influence of the isovector-scalar meson on the spinodal instabilities and the distillation effect in asymmetric non-homogenous nuclear matter under strong magnetic fields, of the order of 10 18 − 10 19 G. Relativistic nuclear models both with constant couplings (NLW) and with density dependent parameters (DDRH) are considered. A strong magnetic field can have large effects on the instability regions giving rise to bands of instability and wider unstable regions. It is shown that for neutron rich matter the inclusion of the δ meson increases the size of the instability region for NLW models and decreases it for the DDRH models. The effect of the δ meson on the transition density to homogeneous β-equilibrium matter is discussed. The DDRHδ model predicts the smallest transition pressures, about half the values obtained for NLδ.
The effect of the density dependence of the nucleonic equation of state and the hyperon meson cou... more The effect of the density dependence of the nucleonic equation of state and the hyperon meson couplings on the star properties, including strangeness content, mass and radius, are studied within a relativistic mean field formalism. It is shown that there is still lacking information on the nucleonic equation of state at supra-saturation densities and on the hyperon interactions in nuclear matter that will allow a clear answer to the question whether the mass of the pulsar J1614-2230 could rule out exotic degrees of freedom from the interior of compact stars. We show that some star properties are affected in a similar way by the density dependence of the symmetry energy and the hyperon content of the star. To disentangle these two effects it is essential to have a good knowledge of the equation of state at supra-saturation densities. A linear correlation between the radius and the strangeness content of a star with a fixed mass is obtained.
The Landau Fermi Liquid parameters are calculated for charge neutral asymmetric nuclear matter in... more The Landau Fermi Liquid parameters are calculated for charge neutral asymmetric nuclear matter in beta equilibrium at zero temperature in the presence of a very strong magnetic field with relativistic mean-field models. Due to the isospin structure of the system, with different populations of protons and neutrons and spin alignment to the field, we find nonvanishing Landau mixing parameters. The existence of quantized Landau levels for the charged sector has some impact on the Landau parameters with the presence of discretized features in those involving the proton sector. Using the Fermi liquid formalism singlet and triplet excited quasiparticle states are analyzed, and we find that in-medium effects and magnetic fields are competing, however, the former are more important in the interaction energy range considered. It is found that for magnetic field strengths Log 10 B (G) ≤ 17 the relative low polarization of the system produces mild changes in the generalized Landau parameters with respect to the unmagnetized case, while for larger strengths there is a resolution of the degeneracy of the interaction energies of quasiparticles in the system.
The Self-consistent random phase approximation (SCRPA) is applied to the exactly solvable model w... more The Self-consistent random phase approximation (SCRPA) is applied to the exactly solvable model with fermion boson coupling proposed by Schütte and Da-Providencia. Very encouraging results in comparison with the exact solution of the model for various observables are obtained. The transition from the normal phase to the phase with a spontaneously broken symmetry is carefully investigated. The strong reduction of the variance in SCRPA vs HF is pointed out.
We study the effect of strong magnetic fields, of the order of 10 18 − 10 19 G, on the instabilit... more We study the effect of strong magnetic fields, of the order of 10 18 − 10 19 G, on the instability region of nuclear matter at subsaturation densities. Relativistic nuclear models both with constant couplings and with density dependent parameters are considered. It is shown that a strong magnetic field can have large effects on the instability regions giving rise to bands of instability and wider unstable regions. As a consequence we predict larger transition densities at the inner edge of the crust of compact stars with strong magnetic field. The direction of instability gives rise to a very strong distillation effect if the last Landau level is only partially filled. However, for almost completed Landau levels an anti-distillation effect may occur.
We investigate the effects of strong magnetic fields on the equation of state of warm stellar mat... more We investigate the effects of strong magnetic fields on the equation of state of warm stellar matter as it may occur in a protoneutron star. Both neutrino free and neutrino trapped matter at a fixed entropy per baryon are analyzed. A relativistic meanfield nuclear model, including the possibility of hyperon formation, is considered. A density dependent magnetic field with the magnitude 10 15 G at the surface and not more than 3 × 10 18 G at the center is considered. The magnetic field gives rise to a neutrino suppression, mainly at low densities, in matter with trapped neutrinos. It is shown that an hybrid protoneutron star will not evolve to a low mass blackhole if the magnetic field is strong enough and the magnetic field does not decay. However, the decay of the magnetic field after cooling may give rise to the formation of a low mass blackhole.
The chiral model is used to describe quark matter under strong magnetic fields and compared to ot... more The chiral model is used to describe quark matter under strong magnetic fields and compared to other models, the MIT bag model and the two flavor Nambu-Jona-Lasinio model. The effect of vacuum corrections due to the magnetic field is discussed. It is shown that if the magnetic field vacuum corrections are not taken into account explicitly the parameters of the models should be fitted to low density meson properties in the presence of the magnetic field.
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Papers by Aziz Rabhi