Neutron stars in a class of non-linear relativistic models

Abstract

We introduce in this work a class of relativistic models for nuclear matter and neutron stars which exhibits a parameterization, through mathematical constants, of the non-linear meson-baryon couplings. For appropriate choices of the parameters, it recovers current QHD models found in the literature: Walecka and the Zimanyi and Moszkowski models (ZM and ZM3). For other choices of the parameters, the new models give very interesting and new physical results.We have obtained numerical values for the maximum mass and radius of a neutron star sequence, red-shift, hyperon populations, radial distribution of particles, among other relevant static properties of these stellar objects. The phenomenology of neutron stars in ZM models is presented and compared to the phenomenology obtained in other versions of the Walecka model. We have found that the ZM3 model is too soft and predicts a very small maximum neutron star mass, $\sim0.72 M_\odot$. A strong similarity between the results of ZM-like models and those with exponential couplings is noted. Sensibility of the results to the specific choice of the values for the binding energy and saturation density is pointed out. Finally, we discuss the very intense scalar condensates found in the interior of neutron stars which may lead to negative effective masses.