arXiv subjects

Odilon Lourenço

Publications and source records attributed to Odilon Lourenço.

27 records · Page 2Linked to original sources

arXiv2021

Short-range correlations effects on the deformability of neutron stars

In the present work, we investigate the effects of short-range correlations (SRC) on the dimensionless deformability of the binary neutron system related to the GW170817 event. We implemented phenomenological SRC in a relativistic mean-field model in which the bulk parameters, namely, incompressibility ($K_0$), effective nucleon mass ratio ($m^*$), symmetry energy ($J$) and its slope ($J_0$), are independently controlled. Our results point out that the SRC favor the model to pass through the constraints, established by the LIGO/Virgo Collaboration, on the values of $Λ_{1.4}$ and on the $Λ_1\timesΛ_2$ region. We also found a clear linear correlation between $Λ_{1.4}$ with $K_0$ and $L_0$ (increasing dependence), and with $m^*$ and $J$ (decreasing dependence). Finally, we also obtained compatible numbers for $R_{1.4}$ (model with and without SRC) in comparison with recent data from the neutron star interior composition explorer mission.

nucl-th↗

arXiv2021

Thermodynamical phases in a PNJL model at zero temperature

The confinement/deconfinement transition described the Polyakov-Nambu-Jona-Lasinio (PNJL) model is extended to be operative at zero temperature regime. In this study, the scalar and vector channel interaction strengths of the original PNJL model are modified by introducing a dependence on the traced Polyakov loop. In such a way the effective interactions depend on the quark phase and in turn provides a backreaction of the quarks to the gluonic sector, also at zero temperature. On general grounds from quantum chromodynamics this is an expected feature. The thermodynamics of the extended model (PNJL0) is studied in detail. It presents along with a suitable choice of the Polyakov potential, a first order confined/deconfined quark phase transition even at $T=0$. We also show that the vector channel plays an important role in order to allow $Φ\ne0$ solutions for the PNJL0 model. Furthermore, the sensitivity of the combined quarkyonic and deconfinement phases to the vector interaction strength and the proposed parametrization of the Polyakov-loop potential at $T=0$ allowed to set a window for the bulk values of the relevant parameters.

hep-ph↗

arXiv2020

Short-range correlation effects on the neutron star cooling

Short range correlations (SRC) have been known to be an important aspect of nuclear theory for some time. Recent works have re-ignited interest on this topic, particularly due to the fact that it has recently been demonstrated that SRC may be responsible for breaking pairing gaps in nuclear matter. In this work we revisit the concept of SRC for beta equilibrated matter in neutron stars. We construct two equivalent models, with and without SRC and proceed to investigate the thermal evolution of stars described by such models. We show that SRC play a major role in the thermal evolution of neutron stars. It will be shown that while the SRC largely leaves the macroscopic properties of the star unaltered, it significantly alters the proton fraction, thus leading to an early onset of the direct Urca (DU) process, which in turns leads to stars exhibiting much faster cooling.

nucl-th↗

arXiv2020

Revisiting the thermal relaxation of neutron stars

In this work we revisit the thermal relaxation process for neutron stars. Such process is associated with the thermal coupling between the core and the crust of neutron stars. The thermal relaxation, which takes place at around 10 -- 100 years, is manifested as a sudden drop of the star's surface temperature. Such drop is smooth for slow cooling objects and very sharp for those with fast cooling. In our study we focus particularly on the cooling of neutron stars whose mass is slightly greater than the value above which the direct Urca (DU) process sets in. Considering different mechanisms for neutrino production in each region of the star, and working with equations of state with different properties, we solve the thermal evolution equation and calculate the thermal relaxation time for ample range of neutron star masses. By performing a comprehensive study of neutron stars just above the onset of the direct Urca process we show that stars under these conditions exhibit a peculiar thermal relaxation behavior. We demonstrate that such stars exhibit an abnormally late relaxation time, characterized by a second drop of its surface temperature taking place a later ages. We qualify such behavior by showing that it is associated with limited spatial distribution of the DU process is such stars. We show that as the star's mass increase, the DU region also grows and the start exhibits the expected behavior of fast cooling stars. Finally we show that one can expect high relaxation times for stars in which the DU process takes place in a radius not larger than 3 km.

astro-ph.HE↗

arXiv2019

Neutron star cooling and GW170817 constraint within quark-meson coupling models

In the present work we used five different versions of the quark-meson coupling (QMC) model to compute astrophysical quantities related to the GW170817 event and to neutron star cooling process. Two of the models are based on the original bag potential structure and three versions consider a harmonic oscillator potential to confine the quarks. The bag-like models also incorporate the pasta phase used to describe the inner crust of neutron stars. We show that the pasta phase always play a minor or negligible role in all studies. Moreover, while no clear correlation between the models that satisfy the GW170817 constraints and the slope of the symmetry energy is found, a clear correlation is observed between the slope and the fact that the cooling is fast or slow, i.e., fast (slow) cooling is related to higher (lower) values of the slope. We did not find one unique model that can describe, at the same time, GW170817 constraints and give a perfect description of the possible cooling processes.

astro-ph.HE↗

arXiv2019

Consistent relativistic mean field models constrained by GW170817

We have obtained the Love number and corresponding tidal deformabilites ($Λ$) associated with the relativistic mean-field parametrizations shown to be consistent (CRMF) with the nuclear matter, pure neutron matter, symmetry energy and its derivatives [Dutra, et al., Phys. Rev. C 90, 055203 (2014)]. Our results show that CRMF models present very good agreement with the recent data from binary neutron star merger event GW170817. They also confirm the strong correlation between $Λ_{1.4}$ and the radius of canonical stars ($R_{1.4}$). When a recently GW170817 constraint on $Λ_{1.4}$ and the corresponding radius $R_{1.4}$ is used, the majority of the models tested are shown to satisfy it.

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arXiv2018

The symmetry energy $γ$ parameter of relativistic mean-field models

The relativistic mean-field models tested in previous works against nuclear matter experimental values, critical parameters and macroscopic stellar properties are revisited and used in the evaluation of the symmetry energy $γ$ parameter obtained in three different ways. We have checked that independent of the choice made to calculate the $γ$ values, a trend of linear correlation is observed between $γ$ and the symmetry energy ($\mathcal{S}_0$) and a more clear linear relationship is established between $γ$ and the slope of the symmetry energy ($L_0$). These results directly contribute to the arising of other linear correlations between $γ$ and the neutron star radii of $R_{1.0}$ and $R_{1.4}$, in agreement with recent findings. Finally, we have found that short-range correlations induce two specific parametrizations, namely, IU-FSU and DD-ME$δ$, simultaneouslycompatible with the neutron star mass constraint of $1.93 < M_{max}/M_\odot < 2.05$ and with the overlap band for the $L_0\times\mathcal{S}_0$ region, to present $γ$ in the range of $γ=0.25\pm0.05$.

nucl-th↗

arXiv2016

Stellar properties and nuclear matter constraints

We have analyzed stellar properties of the relativistic mean-field (RMF) parametrizations shown to be consistent with the recently studied constraints related to nuclear matter, pure neutron matter, symmetry energy and its derivatives [Dutra et al., Phys. Rev. C 90, 055203 (2014)]. Our results show that only two RMF parametrizations do not allow the emergence of the direct Urca process, important aspect regarding the evolution of a neutron star. Moreover, among all approved RMF models, fourteen of them produce neutron stars with maximum masses inside the range $1.93\leqslant M/M_\odot\leqslant 2.05$, with $M_\odot$ being the solar mass. Only three models yield maximum masses above this range and a discussion on the inclusion of hyperons is presented. Finally, we have verified that the models satisfying the neutron star maximum mass constraint do not observe the squared sound velocity bound, namely, $v_s^2 < 1/3$, corroborating recent findings. However, the recently proposed $σ$-cut scheme can make the RMF models consistent with both constraints depending on the isoscalar-vector interaction of each parametrization.

astro-ph.HE↗

arXiv2016

Summary of the 2015 LHCb workshop on multi-body decays of D and B mesons

This document contains a summary of the LHCb workshop on multi-body decays of D and B mesons, held at CBPF, Rio de Janeiro, in July 2015. The workshop was focused on issues related to amplitude analysis of three- and four-body hadronic decays. In addition to selected LHCb results, contributions from guest theorists are included.

hep-ex↗