Impact of dark energy on the structure of neutron stars: The vacuum case

TL;DR

This paper explores how a vacuum dark energy component influences neutron star structure, revealing significant effects on mass-radius relationships and discussing observational constraints on vacuum energy within these stars.

Contribution

It introduces a model incorporating vacuum energy into neutron star structure, analyzing its impact on mass-radius relations with novel inhomogeneous vacuum distributions.

Findings

Vacuum energy significantly alters neutron star mass-radius curves.

Inclusion of vacuum energy affects maximum neutron star masses.

Observational data constrains the amount of vacuum energy in neutron stars.

Abstract

The potential role of a cosmic vacuum dark component in the properties of neutron stars is investigated. It is assumed that the static, spherically symmetric distribution of matter within neutron stars is supported by two distinct components: ordinary matter and a vacuum fluid. For normal matter we use a set of state-of-the-art nuclear matter equations of state, each grounded in nuclear physics experiments. The vacuum energy component is inhomogeneously distributed within the star and obeys the standard equation of state ($p_v = -\epsilon_v$). This is characterized by an energy density fraction $y = \epsilon_m/ (\epsilon_m + \epsilon_v)$, which we model as either a constant or radius-dependent. Our findings reveal that the inclusion of vacuum energy significantly affects the mass-radius relationships in neutron stars, influencing both the maximum achievable masses and the qualitative form of these relationships. Some constraints from current multimessenger observational data limiting the amount of vacuum energy within neutron stars are also discussed.