Modeling quasar central engine as a relativistic radiating star

Беешам

2018

Eur. Phys. J. C

In this paper, we have derived a spatially flat homogeneous and isotropic cosmological model in f (R, T φ ) gravity with a scalar field. In addition to a minimally coupled scalar field with self interacting potential, we also have a contribution from the coupling of the geometry and the field. We have reconstructed a form of f (R, T φ ) by requiring the conservation of energy-momentum tensor of the scalar field. The behavior of the reconstructed f (R, T φ ) gravity is examined for a flat potential as well as a massless scalar field model. The evolution of the universe is studied via the deceleration and equation of state parameters. The promising feature of the model is the transition behavior of the universe from deceleration to the present acceleration.

Section: Introductionmentioning

confidence: 88%

“…The theoretical and observational investigation of scalar field models is an essential task in cosmology. Recently, Singh and Singh [69] have reconstructed flat scalar and exponential potential models of f (R, T ) gravity in scalar field cosmology.…”

Section: Introductionmentioning

confidence: 99%

The $$f(R,T^\phi )$$ f ( R , T ϕ ) gravity models with conservation of energy–momentum tensor

Беешам

2018

Eur. Phys. J. C

“…The field equations of f (R, T ) gravity with minimally couples scalar field φ in a gravitational action self interacting through potential V (φ) is given as [46]…”

Section: Gravitational Field Equations Of F (R T ) Gravity With Scalmentioning

confidence: 99%

“…and [46] along with other parameters as in figure. It is noticed that higher the value of β, higher becomes value of the scalar field potential (see Fig.7 and Fig.8) and cosmological constant (see Fig.9 and Fig.10).…”

Section: Exponential Scalar Potentialmentioning

confidence: 99%

Scalar field and time varying cosmological constant in f ( R , T ) gravity for Bianchi type-I universe

Chinese Journal of Physics

Bishi

Sahoo

2016

In this article, we have analysed the behaviour of scalar field and cosmological constant in f (R, T ) theory of gravity. Here, we have considered the simplest form of f (R, T ) i.e. f (R, T ) = R + 2f (T ), where R is the Ricci scalar and T is the trace of the energy momentum tensor and explored the spatially homogeneous and anisotropic Locally Rotationally Symmetric (LRS) Bianchi type-I cosmological model. It is assumed that the Universe is filled with two non-interacting matter sources namely scalar field (normal or phantom) with scalar potential and matter contribution due to f (R, T ) action. We have discussed two cosmological models according to power law and exponential law of the volume expansion along with constant and exponential scalar potential as sub models. Power law models are compatible with normal (quintessence) and phantom scalar field whereas exponential volume expansion models are compatible with only normal (quintessence) scalar field. The values of cosmological constant in our models are in agreement with the observational results. Finally, we have discussed some physical and kinematical properties of both the models.

“…Recently analytical solutions with anisotropic matter in isotropic coordinate have been discussed by Pant et al (2014), Newton Singh et al (2015a). Newton Singh and Pant (2015) also discuss an exact solution in conformally flat metric representing a central engine of a quasar. Reddy et al (2015) also presented a model of gravitational collapse which discussed the impact of anisotropic stresses during dissipative collapse.…”

Section: Introductionmentioning

confidence: 99%

Charged anisotropic superdense stars with constant stability factor

Pant

2015

Astrophys Space Sci

Self Cite

In this paper, we have presented charged anisotropic Vlasenko-Pronin solutions and a new charged anisotropic Schwarzschild interior solution of the general relativistic field equations in curvature coordinates. These exact solutions are stable and well behaved in all respects for a wide range of anisotropy parameter and charge parameter. These new solutions can be used to model charged, anisotropic neutron stars and quark stars whose masses are comparatively heavier. An interesting fact of these solutions is that their stability factors |v 2 ⊥ − v 2 r | < 1 are constants. Also, we have presented a new and first solution where radial pressure is greater than transverse pressure (i.e. p r − p ⊥ > 0). For a neutral solution it reduces to the Schwarzschild interior solution with constant density. Our charged analogue of the Schwarzschild solution has density decreasing outward to the surface of the star which is necessary for a physical star. The EOSs corresponding to the presented solutions are also studied with their stiffness or softness by comparing their compression moduli. Furthermore, these compression moduli are decreasing outwards from the center. We expect this as the core must be very compact compared to its surface.