Cosmological Constant Effects on the Properties of Mass Twin Compact Stars

TL;DR

This paper explores how the cosmological constant influences the internal structure and observable properties of mass twin compact stars, revealing effects that can alter their mass-radius relationship and mimic phase transition phenomena.

Contribution

It introduces a systematic analysis of the cosmological constant's impact on compact star properties, especially mass twins, within Einstein's gravity framework, highlighting effects similar to pasta phases.

Findings

Certain values of $\Lambda$ modify star mass and radius.

$\Lambda$ effects can mimic pasta phase phenomena.

Inclusion of $\Lambda$ influences the mass-radius diagram of compact stars.

Abstract

We present a systematic investigation of the cosmological constant effects in compact stars interiors in the framework of Einstein's gravity. Consideration of a cosmological constant $\Lambda$ in compact stars is motivated by the mechanism of acceleration of the observable universe, where $\Lambda$ is usually related to the dark energy. In particular, we consider compact star mass twins, hybrid neutron stars that populate both the second and third branch of the mass-radius diagram. For those models, the need of consideration of excluded volume effects in the equation of state, resulting from the finite size volume of nucleons, leads to a stiffening of matter causing compact stars to acquire higher mass and radius values. We demonstrate that certain values of the cosmological constant can also modify the compact star properties but in an opposite way. In addition, we find that the inclusion of $\Lambda$ can have a similar effect to the existence of pasta phases at the hadron-quark interface.