Emerging anisotropic compact stars in $$f(\mathcal {G},T)$$ f ( G , T ) gravity

Abstract

The possible emergence of compact stars has been investigated in the recently introduced modified GaussBonnet f (G, T ) gravity, where G is the Gauss-Bonnet term and T is the trace of the energy-momentum tensor (Sharif and Ikram, Eur Phys J C 76:640, 2016). Specifically, for this modified f (G, T ) theory, the analytic solutions of Krori and Barua have been applied to an anisotropic matter distribution. To determine the unknown constants appearing in the Krori and Barua metric, the well-known three models of the compact stars, namely 4U1820-30, Her X-I, and SAX J 1808.4-3658 have been used. The analysis of the physical behaviour of the compact stars has been presented and the physical features like energy density and pressure, energy conditions, static equilibrium, stability, measure of anisotropy, and regularity of the compact stars, have been discussed.

Non-trivial class of anisotropic compact stellar model in Rastall gravity

“…The stellar structure topic has been developed over many years either in Newtonian gravity or later in General Relativity (GR) since the firstly obtained exterior/interior solution of a spherically symmetric object [1,2]. Motivated by the claim that pressure at core of the compact star model could have anisotropic structure where the density exceeds the nuclear a e-mail: nashed@bue.edu.eg b e-mail: waleed.elhanafy@bue.edu.eg (corresponding author) density ∼ 10 15 g/cm 3 , many models have been developed imposing the anisotropic pressure concept (assuming radial and tangential pressures are different) to derive realistic stellar models within the GR context [3] (see also [4][5][6][7][8][9][10][11][12][13][14][15]) and in modified gravity as well [16][17][18][19][20][21][22][23][24][25][26]. Possible sources of anisotropy of ultra-compact stars could be due to solidification [27], superfluidity [28], strong magnetic fields [29], hyperons [30], pion-condesation [31] and strong interactions [32].…”

Ricci inverse anisotropic stellar structures

“…However, while investigating the compact objects in some alternative gravity theories, modified Tolman-Oppenheimer-Volkoff equations with zero pressure and energy density, the solution outside the star can differ from Schwarzschild's solution. Thus, it is expected that the solutions of the modified Tolman-Oppenheimer-Volkoff equations with non-zero energy density and pressure may accommodate Schwarzschild's geometry with some specific choice of modified gravity model [59][60][61][62][63]. Perhaps this might be the reason or justification that Birkhoff's theorem may not hold in alternative theories of gravity.…”

Relativistic polytropic models of charged anisotropic compact objects

“…[31][32][33][34]. Recently, several researchers have made phenomenological considerations in the assessments of the physical influence of anisotropic stress within the realm of the , as well as alternative gravitational theories [35][36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53].…”