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arXiv · 2212.09485

Modified Gauge Invariant Einstein Maxwell Gravity and Stability of Spherical perfect fluid Stars with Magnetic Monopoles

Hossein Ghaffarnejad·Leyla Naderi
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Abstract

As an alternative gravity model we consider an extended Einstein-Maxwell gravity containing a gauge invariance property. Extension is assumed to be addition of a directional coupling between spatial electromagnetic fields with the Ricci tensor. We will see importance of the additional term in making a compact stellar object and value of its radius. As an application of this model we substitute ansatz of magnetic field of a hypothetical magnetic monopole which has just time independent radial component and for matter part we assume a perfect fluid stress tensor. To obtain spherically symmetric internal metric of the perfect fluid stellar compact object we solve Tolman-Oppenheimer-Volkoff equation with a polytropic form of equation of state as $p(\rho)=a\rho^2$. Using dynamical system approach we study stability of the solutions for which arrow diagrams show saddle (quasi stable) for $a<0$ (dark stars) and sink (stable) for $a>0$ (normal visible stars). We check also the energy conditions, speed of sound and Harrison-Zeldovich-Novikov static stability criterion for obtained solution and confirm that they make stable state.

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Hossein Ghaffarnejad, Leyla Naderi. 2022-12-19. Modified Gauge Invariant Einstein Maxwell Gravity and Stability of Spherical perfect fluid Stars with Magnetic Monopoles. https://doi.org/10.22128/ijaa.2024.759.1175

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