Constraints set on key parameters of the nuclear matter equation of state (EoS) by the values of the tidal deformability, inferred from GW170817, are examined by using a diverse set of relativistic and nonrelativistic mean-field models. These models are consistent with bulk properties of finite nuclei as well as with the observed lower bound on the maximum mass of neutron star $\approx 2M_{\odot }$. The tidal deformability shows a strong correlation with specific linear combinations of the isoscalar and isovector nuclear matter parameters associated with the EoS. Such correlations suggest that a precise value of the tidal deformability can put tight bounds on several EoS parameters, in particular on the slope of the incompressibility and the curvature of the symmetry energy. The tidal deformability obtained from the GW170817 and its UV, optical and infrared counterpart sets the radius of a canonical $1.4M_{\odot }$ neutron star to be $11.82\le R_{1.4}\le 13.72\mathrm{km}$.

We investigate the probable existence of dark matter in the interior of neutron stars. Despite the current state of knowledge, the observational properties of neutron stars have not definitively ruled out the possibility of dark matter. Our research endeavors to shed light on this intriguing mystery by examining how certain neutron star properties, including mass, radius, and tidal deformability, might serve as constraints for the dark matter model. In our investigation, we adopt a two-fluid approach to calculate the properties of neutron stars. For the nuclear matter equation-of-state (EOS), we employ several realistic EOS derived from the relativistic mean field model (RMF), each exhibiting varying stiffness and composition. In parallel, we look into the dark matter EOS, considering fermionic matter with repulsive interaction described by a relativistic mean field Lagrangian. A reasonable range of parameters is sampled meticulously. Our study primarily focuses on exploring correlations between the dark matter model parameters and different neutron star properties using a rich set of EOSs. Interestingly, our results reveal a promising correlation between the dark matter model parameters and stellar properties, particularly when we ignore the uncertainties in the nuclear matter EOS. However, when introducing uncertainties in the nuclear sector, the correlation weakens, suggesting that the task of conclusively constraining any particular dark matter model might be challenging using global properties alone, such as mass, radius, and tidal deformability. Notably, we find that dark-matter admixed stars tend to have higher central baryonic density, potentially allowing for non-nucleonic degrees of freedom or direct Urca processes in stars with lower masses. There is also a tantalizing hint regarding the detection of stars with the same mass but different surface temperatures, which may indicate the presence of dark matter. With our robust and extensive dataset, we delve deeper and demonstrate that even in the presence of dark matter, the semiuniversal C-Love relation remains intact. This captivating finding adds another layer of complexity to the interplay between dark matter and neutron star properties. Published by the American Physical Society 2024

The agreement of the nuclear equation of state (EOS) deduced from the GW170817-based tidal deformability with the one obtained from empirical data on microscopic nuclei is examined. It is found that suitably chosen experimental data on isoscalar and isovector modes of nuclear excitations together with the observed maximum neutron star mass constrain the EOS which displays a very good congruence with the GW170817 inspired one. The giant resonances in nuclei are found to be instrumental in limiting the tidal deformability parameter and the radius of a neutron star in somewhat narrower bounds. At the $1\sigma$ level, the values of the canonical tidal deformability ${\mathrm{\Lambda }}_{1.4}$ and the neutron star radius $R_{1.4}$ come out to be $267\pm 144$ and $11.6\pm 1.0$ km, respectively.

We study the effect of rotation on global properties of neutron star with a hyperon core in an effective chiral model with varying nucleon effective mass within a mean field approach. The resulting gross properties of the rotating compact star sequences are then compared and analyzed with other theoretical predictions and observations from neutron stars. The maximum mass of the compact star predicted by the model lies in the range $(1.4-2.4) ~M_{\odot}$ at Kepler frequency $\Omega_K$, which is consistant with recent observation of high mass stars thereby reflecting the sensitivity of the underlying nucleon effective mass in the dense matter EoS. We also discuss the implications of the experimental constraints from the flow data from heavy-ion collisions on the global properties of the rotating neutron stars.Comment: 11 Pages, 10 Figures and 2 Table

Context. The equation of state (EOS) for neutron stars is modeled using the relativistic mean field (RMF) approach with a mesonic nonlinear (NL) interaction, a modified sigma potential (NL–σ cut) that mimics the effect of an exclusion volume or the onset of a quarkyonic phase, and influences of dark matter in the NL (NL DM). Experimental constraints on the general properties of finite nuclei and heavy ion collisions, as well as astrophysical observations of neutron star radii and tidal deformation are taken into account. Aims. We evaluate the plausibility and implications of each scenario by exploring how modifications to the RMF model, including the NL–σ cut and dark matter influences, affect the neutron star EOS. Additionally, the study examines the tension between the PREX-II experimental data and other constraints, aiming to identify which model is able to optimally reconcile the available experimental and observational evidence. Methods. A Bayesian analysis framework was employed to systematically compare the different EOS scenarios. This approach integrates constraints from nuclear experiments (finite nuclei properties and heavy ion collisions) and astrophysical observations (neutron star radii, tidal deformation, and PSR J0437–4715 measurements) to rigorously assess the viability of each model. Results. The analysis shows that including the PREX–II data renders all models less favorable, indicating significant tension with the other constraints and incompatibility with chiral effective field theory calculations of pure neutron matter. When excluding PREX–II, the NL–σ cut model emerges with the highest Bayes evidence, favoring a stiffening of the EOS at high densities, whereas the model incorporating a dark matter component is the least favorable. Furthermore, new PSR J0437–4715 measurements lead to an approximate 0.2 km reduction in the 90% confidence interval upper boundary for neutron star radii, along with a notable decrease in Bayesian evidence, suggesting potential conflicts with prior data and/or the need for more adaptable models.