Propagation of polar gravitational waves in f(R, T) scenario

Sharif, M.; Siddiqa, Aisha

doi:10.1007/s10714-019-2558-6

Cited by 46 publications

(25 citation statements)

References 62 publications

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“…Our investigations reveal that the polar perturbations (even with η = 0) involve far more complicated couplings among the perturbing elements than the axial perturbations to the Kantowski-Sachs background and also their FLRW counterparts. Unlike in the case of FLRW background [14,18,20], no polar perturbation equation in a single variable can be derived in our case. This poses difficulty in finding analytical solutions for the polar modes.…”

Section: Discussionmentioning

confidence: 99%

“…Let us consider the perturbed metric in presence of matter. The perturbations in the energy density and pressure of the fluid can be written as in the FRLW case [14,19,20] as follows:…”

Section: Perturbed Energy-momentum Tensormentioning

confidence: 99%

“…In the present paper, we adopt the RW gauge to investigate axial as well as polar waves in Kantowski-Sachs spacetime. Similar studies incorporating the RW perturbation scheme have been undertaken with FLRW metric as the background [13][14][15][18][19][20][21][22]. Perturbations on KS model have been discussed in some other papers [34,48,49], but the RW gauge has not been employed before.…”

Section: Introductionmentioning

confidence: 97%

“…In [18], he has shown that the general solution of the perturbation equations can be expressed in terms of two copies of a single master scalar that obeys scalar wave equation on the FLRW background (with a Regge-Wheeler / Zerilli type potential), and characterises the two gravitational degrees of freedom, with one scalar satisfying a transport type equation representing the matter perturbation. The propagation of axial and polar waves using the RW gauge in FLRW spacetime has been discussed by Sharif and Siddiqa in the context of f (R, T ) gravity [19,20] and by Salti et al in Rastall gravity [21,22]. In another paper [23], GWs produced by axially symmetric dissipative dust was examined in the context of f (R) gravity.…”

Section: Introductionmentioning

confidence: 99%

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Propagation of Axial and Polar Gravitational Waves in Kantowski-Sachs Universe

Datta,

Guha

2021

Preprint

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In this paper, we apply the Regge-Wheeler formalism in our study of axial and polar gravitational waves in Kantowski-Sachs universe. The background field equations and the linearised perturbation equations for axial and polar modes are derived in presence of matter. To find the analytical solutions, we analyse the propagation of waves in vacuum spacetime. The background field equations in absence of matter are first solved by assuming that the expansion scalar Θ to be proportional to the shear scalar σ (so that the metric coefficients are given by the relation a = b n , where n is an arbitrary constant). Using the method of separation of variables, the axial perturbation parameter h 0 (t, r) is obtained from its wave equation. The other perturbation h 1 (t, r) is then determined from h 0 (t, r). We observe that the anisotropy of the background spacetime is responsible for the damping of the axial waves propagating through it. On the other hand, the polar perturbation equations are much more involved compared to their FLRW counterparts, as well as to the axial perturbations in Kantowski-Sachs background. The polar equations contain complicated couplings among the perturbation variables. In both the axial and polar cases, the radial and temporal solutions for the perturbations separate out as product. The perturbation equations in presence of matter show that the axial waves can cause perturbations only in the azimuthal velocity of the fluid without deforming the matter field. But the polar waves must perturb the energy density, the pressure and also the non-azimuthal components of the fluid velocity. The propagation of axial and polar gravitational waves in Kantowski-Sachs and Bianchi I spacetimes is found to be more or less similar in nature.

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Section: Discussionmentioning

confidence: 99%

“…Let us consider the perturbed metric in presence of matter. The perturbations in the energy density and pressure of the fluid can be written as in the FRLW case [14,19,20] as follows:…”

Section: Perturbed Energy-momentum Tensormentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

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Propagation of Axial and Polar Gravitational Waves in Kantowski-Sachs Universe

Datta,

Guha

2021

Preprint

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“…In this work we shall work with f (R, T) gravity theory in which the Ricci scalar R is replaced with a suitable functional form of R and trace of energy momentum tensor T [43] and therefore is a straightforward conjecture to f (R) gravity (see [44,45]). f (R, T) gravity have proved to be successful in numerous cosmological sectors such as dark matter [46] dark energy [47], massive pulsars [48,49], super-Chandrasekhar white dwarfs [50], wormholes [51][52][53][54][55][56][57][58][59][60][61], gravitational waves [62][63][64], bouncing cosmology [65,66], baryogenesis [67,68], Big-Bang nucleosynthesis [69] and in varying speed of light scenarios [70]. The article is methodized as follows: In Section II we provide a summary of f (R, T) gravity and solve the field equations assuming a bulk viscous fluid.…”

Section: Introductionmentioning

confidence: 99%

Late-time viscous cosmology in f(R, T) gravity

2021

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The article communicates an alternative route to suffice the late-time acceleration considering a bulk viscous fluid with viscosity coefficient ζ = ζ 0 + ζ 1 H + ζ 2 H 2 , where ζ 0 , ζ 1 , ζ 2 are constants in the framework of f (R, T) modified gravity. We presume the f (R, T) functional form to be f = R + 2αT where α is a constant. We then solve the field equations for the Hubble Parameter and study the cosmological dynamics of kinematic variables such as deceleration, jerk, snap and lerk parameters as a function of cosmic time. We observe the deceleration parameter to be highly sensitive to α and undergoes a signature flipping at around t ∼ 10 Gyrs for α = −0.179 which is favored by observations. The EoS parameter for our model assumes values close to −1 at t 0 = 13.7Gyrs which is in remarkable agreement with the latest Planck measurements. Next, we study the evolution of energy conditions and find that our model violate the Strong Energy Condition in order to explain the late-time cosmic acceleration. To understand the nature of dark energy mimicked by the bulk viscous baryonic fluid, we perform some geometrical diagnostics like the {r, s} and {r, q} plane. We found the model to mimic the nature of a Chaplygin gas type dark energy model at early times while a Quintessence type in distant future. Finally, we study the violation of continuity equation for our model and show that in order to explain the cosmic acceleration at the present epoch, energymomentum must violate.

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Primordial gravity waves in a rainbow background

Saltı

Aydoğdu

2023

Gen Relativ Gravit

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Propagation of polar gravitational waves in f(R, T) scenario

Cited by 46 publications

References 62 publications

Propagation of Axial and Polar Gravitational Waves in Kantowski-Sachs Universe

Propagation of Axial and Polar Gravitational Waves in Kantowski-Sachs Universe

Late-time viscous cosmology in f(R, T) gravity

Primordial gravity waves in a rainbow background

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