Anisotropic stellar modeling with clouds of string and quintessence field in Rastall gravity

Abstract

This paper proposes a new framework to investigate the spherically symmetric of anisotropic stars with clouds of strings and quintessence field in Rastall gravity. We develop the field equations in a spherically symmetric space–time with a quintessence field and clouds of string. We utilize the mass and radius of Her X-1, Vela X-1, SMC X-1, SAX J1808 0.4-3658 and 4 U 1538-52, which are well mentioned in the literature. We applied the matching conditions by considering outer space calculated in Rastall gravity to evaluate the constants parameters. To check the stability and physical presence of compact models, we computed the most important features of quintessence stars in the presence of a cloud of strings. We explored characteristics including energy density, quintessence density, radial pressure, tangential pressure gradients, anisotropic factor, energy conditions, sound speeds, TOV forces, EoS components, mass function, compactification and redshift.

Imprints of cloud of strings and quintessence field on compact stellar configurations

“…Moreover, our results in the case of quintessence and the cloud of strings field are less dense than the simple quintessence field. In our recent studies [16,20], we studied the quintessence and the cloud of strings stellar configurations using the ansatz of f (Q) gravity and Rastall gravity, but this study is based upon the paradigm of General relativity. Moreover, our results in this study are denser than the Rastall gravity and less dense than the f (Q) gravity paradigm.…”

“…However, there are six unknowns in each of the three equations, which are η (r), ϑ(r), ρ, p r , p t , ρ q ; hence, it is impossible to determine the explicit solutions. To this end, we have taken into account EoS (16) and metric potential functions η(r), ϑ(r) computed using the Karmarkar condition, which for finite values of r are finite everywhere, given as [67]:…”

“…where, F, B, G are constants in km −2 which are calculated in matching conditions, and b & c are taken as free parameters. By incorporating equations ( 18)- (20) with equations (15)- (17). Then, solving the system of equations for ρ, ρ q , p r , & p t , We get the final field equations, which are given as follows:…”

“…The string-like structures observed inside the compact star could be these exotic materials. It is necessary to emphasize that these features are only theoretical and have not been verified by observations of cloud strings in compact objects [20]. One can find many other studies on compact stars and wormholes in the vicinity of different modified theories and scenarios .…”

“…In contrast to the cosmological constant, quintessence exhibits dynamism, capable of either attraction or repulsion based on the equilibrium between its kinetic and potential energy. The shift from an attractive to a repulsive phase in quintessence is believed to have transpired approximately 10 billion years ago, occurring roughly 3.5 billion years after the occurrence of the Big Bang [16]. The fundamental idea of string theory is that, as opposed to particles, which are zero-dimensional entities, the building blocks of nature are one-dimensional strings.…”