Compact stars with variable cosmological constant in f ( R , T
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ORIGINAL ARTICLE
Compact stars with variable cosmological constant in f (R, T ) gravity M. Ilyas1
Received: 8 August 2020 / Accepted: 29 October 2020 © Springer Nature B.V. 2020
Abstract This paper explores and analyzes a set of solutions describing the interior structure of relativistic compact stellar structures with variable cosmological constant (r). We consider the solution of Krori–Barua space-time to a static spherical symmetric metric. Furthermore, we match our interior stellar structure with the exterior Schwarzschild geometry to determine the values of the constants used in the solution of the Krori–Barua space-time. The numerical values of these constants were determined for a set of different compact stars, and using these constants in our solutions, we have studied the viability of matter content, stability, TOV equations, and surface red-shift; and we predicted some physical aspects like central and surface densities, stresses, masses, and radii. Keywords Variable cosmological constant · Alternate to G.R · Modified theory of gravity · Compact stars
1 Introduction After the advent of general relativity (GR), the structure of celestial compact stellar objects was of great interest, which aroused a significance attention of researchers. The groundbreaking work of Schwarzschild, Tolman, Oppenheimer and Volkoff opened a new window for a deep study of theoretical models of celestial stellar objects. Nowadays, several mathematical models of super-dense stellar objects have been suggested by researchers using both analytical and numerical approaches.
B M. Ilyas
[email protected]
1
Institute of Physics and Electronics, Gomal University, Dera Ismail Khan, 29220, Khyber Pakhtunkhwa, Pakistan
Recent WMAP measurement indicates that dark energy (DE) contributes more than 70% of the total energy of the observable universe, while the rest is dark matter (DM) and baryonic matter (Perlmutter et al. 1998; Riess et al. 2004). Therefore, it is considered that the DE theory is most appropriate to explore the current expansion scenario of the universe and the cosmological constant assumed by Einstein is a better choice to explain this DE theory. Furthermore, we would like to consider the cosmological constant, which has something common in the distribution of matter. In the literature, the mass–radius relationship for a relativistic compact star was calculated in the presence of the cosmological constant (Kalam et al. 2012). Likewise, the anisotropy was evoked as a central feature in the study of compact structures that allowed several researchers to model the structures in a way more physically viable. For other noteworthy work with different characteristics in compact stellar structures see Refs. (Chodos et al. 1974; Li et al. 1999a,b; Mak et al. 2002; Mak and Harko 2003; Usov 2004). Similarly, the concept of a variable cosmological constant has been presented in the literature as an attempt to solve some of the standard problems of the CDM model, such as cosmic correspondence and fine-tuning. Numerous cosmol
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