Exploring physical features of anisotropic strange stars beyond standard maximum mass limit in f(R,T)f\left(R,\mathcal {T}\right)f(R,T) gravity (original) (raw)
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2018
We study a specific model of anisotropic strange stars in the modified f (R, T )-type gravity by deriving solutions to the modified Einstein field equations representing a spherically symmetric anisotropic stellar object. We take a standard assumption that f(R, T ) = R+ 2χT , where R is Ricci scalar, T is the trace of the energy-momentum tensor of matter, and χ is a coupling constant. To obtain our solution to the modified Einstein equations, we successfully apply the ‘embedding class 1’ techniques. We also consider the case when the strange quark matter (SQM) distribution is governed by the simplified MIT bag model equation of state given by pr = 13 (ρ− 4B), where B is bag constant. We calculate the radius of the strange star candidates by directly solving the modified TOV equation with the observed values of the mass and some parametric values of B and χ. The physical acceptability of our solutions is verified by performing several physical tests. Interestingly, besides the SQM, a...
2019
The present work is focused on the investigation of the existence of compact structures describing anisotropic matter distributions within the framework of modified gravity theories, specifically f(R,T) gravity theory. Additionally, we have taken f(R,T) as a linear function of the Ricci scalar R and the trace of the energy-momentum tensor T as f(R,T)=R+2χT,where χ is a dimensionless coupling parameter, and the Lagrangian matter L_m=-1/3(2p_t+p_r), to describe the complete set of field equations for the anisotropic matter distribution. We follow the embedding class one procedure using Eisland condition to obtain a full space-time description inside the stellar configuration. Once the space-time geometry is specified we determine the complete solution of the modified Einstein equations by using the MIT bag model equation of state p_r=1/3(ρ-4B) that describes the strange quark matter (SQM) distribution inside the stellar system, where B denotes a bag constant. The physical validity of ...
Anisotropic strange stars under simplest minimal matter-geometry coupling in the f ( R,T ) gravity
Physical Review D
We study strange stars in the framework of fðR; T Þ theory of gravity. To provide exact solutions of the field equations it is considered that the gravitational Lagrangian can be expressed as the linear function of the Ricci scalar R and the trace of the stress-energy tensor T , i.e. fðR; T Þ ¼ R þ 2χT , where χ is a constant. We also consider that the strange quark matter (SQM) distribution inside the stellar system is governed by the phenomenological MIT bag model equation of state (EOS), given as p r ¼ 1 3 ðρ − 4BÞ, where B is the bag constant. Further, for a specific value of B and observed values of mass of the strange star candidates we obtain the exact solution of the modified Tolman-Oppenheimer-Volkoff (TOV) equation in the framework of fðR; T Þ gravity and have studied in detail the dependence of the different physical parameters, like the metric potentials, energy density, radial and tangential pressures and anisotropy etc., due to the chosen different values of χ. Likewise in GR, as have been shown in our previous work [Deb et al., Ann. Phys. (Amsterdam) 387, 239 (2017)] in the present work also we find maximum anisotropy at the surface which seems an inherent property of the strange stars in modified fðR; T Þ theory of gravity. To check the physical acceptability and stability of the stellar system based on the obtained solutions we have performed different physical tests, viz., the energy conditions, Herrera cracking concept, adiabatic index etc. In this work, we also have explained the effects, those are arising due to the interaction between the matter and the curvature terms in fðR; T Þ gravity, on the anisotropic compact stellar system. It is interesting to note that as the values of χ increase the strange stars become more massive and their radius increase gradually so that eventually they gradually turn into less dense compact objects. The present study reveals that the modified fðR; T Þ gravity is a suitable theory to explain massive stellar systems like recent magnetars, massive pulsars and super-Chandrasekhar stars, which cannot be explained in the framework of GR. However, for χ ¼ 0 the standard results of Einsteinian gravity are retrieved.
1 8 O ct 2 01 7 Relativistic model for anisotropic strange stars
2018
In this article, we attempt to find a singularity free solution of Einstein’s field equations for compact stellar objects, precisely strange (quark) stars, considering Schwarzschild metric as the exterior spacetime. To this end, we consider that the stellar object is spherically symmetric, static and anisotropic in nature and follows the density profile given by Mak and Harko (2002), which satisfies all the physical conditions. To investigate different properties of the ultra-dense strange stars we have employed the MIT bag model for the quark matter. Our investigation displays an interesting feature that the anisotropy of compact stars increases with the radial coordinate and attains Preprint submitted to Annals of Physics November 12, 2018 its maximum value at the surface which seems an inherent property for the singularity free anisotropic compact stellar objects. In this connection we also perform several tests for physical features of the proposed model and show that these are ...
Relativistic model for anisotropic strange stars
Annals of Physics, 2017
In this article, we attempt to find a singularity free solution of Einstein's field equations for compact stellar objects, precisely strange (quark) stars, considering Schwarzschild metric as the exterior spacetime. To this end, we consider that the stellar object is spherically symmetric, static and anisotropic in nature and follows the density profile given by Mak and Harko (2002), which satisfies all the physical conditions. To investigate different properties of the ultra-dense strange stars we have employed the MIT bag model for the quark matter. Our investigation displays an interesting feature that the anisotropy of compact stars increases with the radial coordinate and attains
Anisotropic strange star with Tolman–Kuchowicz metric under f(R, T) gravity
The European Physical Journal C, 2020
In the current article, we study anisotropic spherically symmetric strange star under the background of f(R, T) gravity using the metric potentials of Tolman–Kuchowicz type (Tolman in Phys Rev 55:364, 1939; Kuchowicz in Acta Phys Pol 33:541, 1968) as \lambda (r)=\ln (1+ar^2+br^4)$$λ(r)=ln(1+ar2+br4) and \nu (r)=Br^2+2\ln C$$ν(r)=Br2+2lnC which are free from singularity, satisfy stability criteria and also well-behaved. We calculate the value of constants a, b, B and C using matching conditions and the observed values of the masses and radii of known samples. To describe the strange quark matter (SQM) distribution, here we have used the phenomenological MIT bag model equation of state (EOS) where the density profile ($$\rho ρ) is related to the radial pressure ($$p_r$$pr) as p_r(r)=\frac{1}{3}(\rho -4B_g)$$pr(r)=13(ρ-4Bg). Here quark pressure is responsible for generation of bag constant B_g$$Bg. Motivation behind this study lies in finding out a non-singular physically acc...
Strange stars in f(R,T) gravity
2017
In this article we try to present spherically symmetric isotropic strange star model under the framework of f(R,T) theory of gravity. To this end, we consider that the Lagrangian density is an arbitrary linear function of the Ricci scalar R and the trace of the energy momentum tensor T given as f(R,T)=R+2χ T. We also assume that the quark matter distribution is governed by the simplest form of the MIT bag model equation of state (EOS) as p=1/3(ρ-4B), where B is the bag constant. We have obtained an exact solution of the modified form of the the Tolman-Oppenheimer-Volkoff (TOV) equation in the framework of f(R,T) gravity theory and studied the dependence of different physical properties, viz., total mass, radius, energy density and pressure on the chosen values of χ. Further, to examine physical acceptability of the proposed stellar model in detail, we conducted different tests, viz. energy conditions, modified TOV equation, mass-radius relation, causality condition etc. We have prec...
A Well-Behaved Anisotropic Strange Star Model
Advances in Mathematical Physics
We obtain a new nonsingular exact model for compact stellar objects by using the Einstein field equations. The model is consistent with stellar star with anisotropic quark matter in the absence of electric field. Our treatment considers spacetime geometry which is static and spherically symmetric. Ansatz of a rational form of one of the gravitational potentials is made to generate physically admissible results. The balance of gravitational, hydrostatic, and anisotropic forces within the stellar star is tested by analysing the Tolman-Oppenheimer-Volkoff (TOV) equation. Several stellar objects with masses and radii comparable with observations found in the past are generated. Our model obeys different stability tests and energy conditions. The profiles for the potentials, matter variables, stability, and energy conditions are well behaved.
Quark stars with isotropic matter in Hořava gravity and Einstein–æther theory
The European Physical Journal C, 2020
We study non-rotating and isotropic strange quark stars in Lorentz-violating theories of gravity, and in particular in Hořava gravity and Einstein-æther theory. For quark matter we adopt both linear and non-linear equations of state, corresponding to the MIT bag model and color flavor locked state, respectively. The new structure equations describing hydrostatic equilibrium generalize the usual Tolman–Oppenheimer–Volkoff (TOV) equations of Einstein’s general relativity. A dimensionless parameter \nu ν measures the deviation from the standard TOV equations, which are recovered in the limit \nu \rightarrow 0$$ν→0. We compute the mass, the radius as well as the compactness of the stars, and we show graphically the impact of the parameter \nu ν on the mass-to-radius profiles for different equations of state describing quark matter. The energy conditions and stability criteria are also considered, and they are all found to be fulfilled.
Strange stars in energy–momentum-conserved f(R,T) gravity
International Journal of Modern Physics D
For the accurate understanding of compact astrophysical objects, the Tolmann–Oppenheimer–Volkoff (TOV) equation has proved to be of great use. Nowadays, it has been derived in many alternative gravity theories, yielding the prediction of different macroscopic features for such compact objects. In this work, we apply the TOV equation of the energy–momentum–conserved version of the [Formula: see text] gravity theory to strange quark stars. The [Formula: see text] theory, with [Formula: see text] being a generic function of the Ricci scalar [Formula: see text] and trace of the energy–momentum tensor [Formula: see text] to replace [Formula: see text] in the Einstein–Hilbert gravitational action, has shown to provide a very interesting alternative to the cosmological constant [Formula: see text] in a cosmological scenario, particularly in the energy–momentum conserved case (a general [Formula: see text] function does not conserve the energy–momentum tensor). Here, we impose the condition...