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 Λ in compact stars is motivated by the mechanism of acceleration of the observable universe, where Λ 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 filnite 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 filnd that the inclusion of Λ can have a similar effect to the existence of pasta phases at the hadron-quark interface.
Highlights
The physics of neutron stars is currently a very active topic of investigation, covering many aspects of the contemporary physics
We take neutron stars as a probe of the possible effects of the cosmological constant as a free parameter, and allow it to vary inside the star, where matter effects might change its strength, in contrast to the conditions existing in vacuum
This equations of state (EoS) model has been introduced in [9] where the authors discuss the high mass twins phenomenon (HMTs) where stars with very similar masses are located in different branches of the mass-radius diagram having considerable different radii (≈ 1 − 2km difference)
Summary
The physics of neutron stars is currently a very active topic of investigation, covering many aspects of the contemporary physics. These include, but , astrophysical processes like energetic emissions, stellar evolution, studying the dense matter properties in compact star interiors, and element nucleosynthesis. Cosmological studies are dedicated to the understanding of the dynamics of universe as a whole as well as considering the role of the fundamental interactions within it In this respect, Λ is one of the necessary ingredients for the description of the observable universe, providing a mechanism for its accelerated expansion, somehow related to the so called dark energy. Our Λ parameter in this study might account for vacuum energy effects [3] as well as to correspond to some alternative gravity theories parameter under certain limits, providing a useful benchmark
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