Quark stars with isotropic matter in Ho\u0159ava gravity and Einstein\u2013\xe6ther theory

Grigorios Panotopoulos,Ilidio Lopes,Daniele Vernieri

doi:10.1140/epjc/s10052-020-8105-5

Abstract

We study non-rotating and isotropic strange quark stars in Lorentz-violating theories of gravity, and in particular in Hořava gravity and Einstein-æther theory. For quark matter we adopt both linear and non-linear equations of state, corresponding to the MIT bag model and color flavor locked state, respectively. The new structure equations describing hydrostatic equilibrium generalize the usual Tolman–Oppenheimer–Volkoff (TOV) equations of Einstein’s general relativity. A dimensionless parameter nu measures the deviation from the standard TOV equations, which are recovered in the limit nu rightarrow 0. We compute the mass, the radius as well as the compactness of the stars, and we show graphically the impact of the parameter nu on the mass-to-radius profiles for different equations of state describing quark matter. The energy conditions and stability criteria are also considered, and they are all found to be fulfilled.

Highlights

In 2009 Horava gravity [1,2] was proposed as a new candidate theory for quantum gravity which explicitly breaks Lorentz invariance at any energy scale by introducing a preferred foliation of spacetime
In this article we investigated the properties of non-rotating strange quark stars with isotropic matter in Lorentz-violating theories of gravity
We have studied quark stars in Horava gravity and Einstein-æther theory, whose deviations from general relativity (GR) are characterized by a single dimensionless parameter ν

Summary

Introduction

In 2009 Horava gravity [1,2] was proposed as a new candidate theory for quantum gravity which explicitly breaks Lorentz invariance at any energy scale by introducing a preferred foliation of spacetime. It has become even more urgent to study the implications and predictions of viable alternative gravity theories at astrophysical scales, in order to explore non-standard scenarios and the possible signatures of deviations from general relativity (GR) to be observed in the forthcoming detections. For all of these reasons in this work we will investigate some astrophysical implications of the theory.

Horava gravity and Einstein-æther theory

Field equations

Vacuum solution

Equation-of-state

Numerical solution of structure equations

Conclusions