Neutron stars in Einstein-$\Lambda$ gravity: the cosmological constant effects

TL;DR

This paper investigates how the cosmological constant affects neutron star properties within Einstein-$\Lambda$ gravity, revealing limits on maximum mass and stability criteria using microscopic equations of state.

Contribution

It introduces a detailed analysis of neutron star structure considering arbitrary cosmological constants, extending previous models to include $\Lambda$ effects in Einstein gravity.

Findings

Maximum neutron star mass is limited to 1.68 solar masses for positive $\Lambda$.

Einstein gravity cannot explain neutron star structures with negative $\Lambda$.

Neutron stars are shown to be dynamically stable under this gravity model.

Abstract

Regarding a $d-$dimensional spherically symmetric line element in the context of Einstein-$\Lambda$ gravity, the hydrostatic equilibrium equation of stars is obtained. Then, by using the lowest order constrained variational (LOCV) method with the AV$18$ potential and employing microscopic many body calculations in the modern equation of state, the structure properties of neutron stars are investigated. Regardless of cosmological point of view and considering arbitrary positive and negative values of the cosmological constant, the maximum mass of the neutron stars and their corresponding radius in $4$-dimensions are computed. The results show that there is an upper limit for the maximum mass of neutron star for positive cosmological constant ($M_{\max }\leq 1.68M_{\odot }$). On the other hand, it is shown that the Einstein gravity cannot explain the structure of neutron star with negative $\Lambda$. Other properties of neutron stars such as; the Schwarzschild radius, average density, compactness and Buchdahl- Bondi bound are studied. In addition, by using the Buchdahl-Bondi bound for neutron stars, stability of these stars is investigated. Finally, the dynamical stability is investigated and shown that the neutron stars follow the dynamical stability in this gravity.