Complexity factor for a class of compact stars in f(R,T)$f(R,T)$ gravity
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ORIGINAL ARTICLE
Complexity factor for a class of compact stars in f (R, T ) gravity G. Abbas1
· Riaz Ahmed1
Received: 14 September 2019 / Accepted: 2 November 2019 © Springer Nature B.V. 2019
Abstract We investigate the concept of complexity factor for a class of compact star in the framework of modified f (R, T ) gravity. We obtain a generic form of hydrostatic equilibrium equation, express the Einstein field equations, mass function and also physical observation for linear form of function f (R, T ) = R + 2λT , where λ is the coupling parameter, R is Ricci scalar and T is trace of energy momentum tensor. We have analyzed the properties of compact astrophysical objects like energy density and anisotropic pressure are affected by changing the values of coupling parameter λ. We obtained numerical outputs of some physical variables for different chosen values of coupling parameter λ to observe the effect of λ on these quantities and show these in tabular form for different compact stars 4U 1820-30, HerX-1, SAXJ 1808.4-3658 and VelaX-12 with radii 10, 7.7, 7.07 and 9.99 respectively. We determine structure scalars with orthogonal splitting of the Riemann tensor and with the help of these scalars the complexity factor can be determined. Furthermore, we have checked some astrophysical sources for vanishing complexity factor. Keywords Complexity factor · Self-gravitating system · f (R, T ) gravity
1 Introduction Modified theories of gravity have been proposed with the purpose of evading the various modern cosmological ob-
B G. Abbas
[email protected] R. Ahmed [email protected]
1
Department of Mathematics, The Islamia University of Bahawalpur, Bahawalpur, Pakistan
servations of Supernovae of Ia, Cosmic Microwave background radiation, baryon acoustic oscillations, the ΛCDM cosmological model and Planck data etc., which disclosed the accelerated expansion of the Universe (Riess et al. 1998; Clifton et al. 2012; Staykov et al. 2014; Padmanabhan 2003; Nojiri and Odintsov 2007; Perlmutter et al. 1999; Copeland et al. 2006). It should be intimated here that the gravity theory is also tested in astrophysical level. In current era, several modified theories of gravity have been introduced but a few theories like f (R), f (T ) and f (R, T ) have received more attention than any other theories of gravity. In all these theories the geometric part has been replaced by generalized functional form instead to changing the source of the Einstein’s field equations. This discovery has now become the most important advancement in modern cosmology due to general relativity that our Universe is filled with ordinary matter and compelling evidence that the expansion of the Universe is speeding up. Modified theories have explained acceleration and that the Universe contains a large amount of dark energy (Turner and Huterer 2007 and Frieman et al. 2008). One theory out of several modified theories of gravity that has achieved a significant concentration for its capability to deal with expanding our Universe in f (R) gravity. Einste
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