Exploring robust correlations between fermionic dark matter model parameters and neutron star properties: A two-fluid perspective

TL;DR

This study investigates correlations between fermionic dark matter parameters and neutron star properties using a two-fluid model, revealing potential links but also highlighting the challenges due to uncertainties in nuclear matter EOS.

Contribution

It introduces a comprehensive two-fluid approach with varied EOSs to analyze dark matter effects on neutron stars, emphasizing the impact of nuclear matter uncertainties on correlations.

Findings

Correlation between dark matter parameters and stellar properties when ignoring nuclear EOS uncertainties

Dark-matter admixed stars exhibit higher central baryonic densities

The semi-universal C-Love relation remains valid even with dark matter presence

Abstract

The current observational properties of neutron stars have not definitively ruled out the possibility of dark matter. In this study, we primarily focus on exploring correlations between the dark matter model parameters and different neutron star properties using a rich set of EOSs. We adopt a two-fluid approach to calculate the properties of neutron stars. For the nuclear matter 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. 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 semi-universal C-Love relation remains intact.