Isotropic compact stars in 4-dimensional Einstein-Gauss-Bonnet gravity coupled with scalar field -- Reconstruction of model

TL;DR

This paper develops a method to reconstruct models of isotropic compact stars within 4D Einstein-Gauss-Bonnet gravity coupled with a scalar field, demonstrating the theory's consistency with observed stellar properties.

Contribution

It introduces a reconstruction technique allowing arbitrary mass-radius relations for compact stars in EGBS theory, highlighting the degeneracy between the equation of state and model functions.

Findings

Constructed models reproduce desired mass-radius relations.

Models satisfy physical conditions for realistic compact stars.

EGBS theory aligns with observational data.

Abstract

Recently, it has been supposed that the Einstein-Gauss- Bonnet theory coupled with scalar field (EGBS) maybe appropriately admit physically viable models of celestial phenomena such that the scalar field effect is active in standard four dimensions. We consider the spherically symmetric and static configuration of the compact star and explain the consequences of the EGBS theory in the frame of stellar modeling. In our formulation, for any given static profile of the energy density $\rho$ with the spherical symmetry and the arbitrary equation of state (EoS) of matter, we can construct the model which reproduces the profile. Because the profile of the energy density determines the mass $M$ and the radius $R_s$ of the compact star, an arbitrary relation between the mass $M$ and the radius $R_s$ of the compact star can be realized by adjusting the potential and the coefficient function of the Gauss-Bonnet term in the action of EGBS theory. This could be regarded as a degeneracy between the EoS and the functions characterizing the model, which tells that only the mass-radius relation is insufficient to constrain the model. For example, we investigate a novel class of analytic spherically symmetric interior solutions by the polytropic EoS. We discuss our model in detail and show that it is in agreement with the necessary physical conditions required for any realistic compact star approving that EGBS theory is consistent with observations.