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Register a new userStability, dark energy parameterization and swampland aspect of Bianchi Type-$ VI_{h}$ cosmological models with f(R, T)-gravity
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Added by
Dr. Anirudh Pradhan
Publication date
2020
fields
Physics
and research's language is
English
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Stability, dark energy (DE) parameterization and swampland aspects for the Bianchi form-$VI_{h}$ universe have been formulated in an extended gravity hypothesis. Here we have assumed a minimally coupled geometry field with a rescaled function of $f(R, T)$ replaced in the geometric action by the Ricci scalar $R$. Exact solutions are sought under certain basic conditions for the related field equations. For the following theoretically valid premises, the field equations in this scalar-tensor theory have been solved. It is observed under appropriate conditions that our model shows a decelerating to accelerating phase transition property. Results are observed to be coherent with recent observations. Here, our models predict that the universes rate of expansion will increase with the passage of time. The physical and geometric aspects of the models are discussed in detail. In this model, we also analyze the parameterizations of dark energy by fitting the EoS parameter $omega(z)$ with redshift. The results obtained would be useful in clarifying the relationship between dark energy parameters. In this, we also explore the correspondence of swampland dark energy. The swampland criteria have also been shown the nature of the scalar field and the potential of the scalar field.
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Anisotropic cosmological models are constructed in $f(R,T)$ gravity theory to investigate the dynamics of universe concerning the late time cosmic acceleration. Using a more general and simple approach, the effect of the coupling constant and anisotropy on the cosmic dynamics have been investigated. Cosmic anisotropy is found affect substantially the cosmic dynamics.
In the present work, we construct the Tsallis holographic quintessence model of dark energy in $f(R, T)$ gravity with Hubble horizon as IR cut-off. In a flat FRW background, the correspondence among the energy density of the quintessence model with the Tsallis holographic density permits the reconstruction of the dynamics and the potentials for the quintessence field. The suggested Hubble horizon infrared cut-off for the THDE density acts for two specific cases: (i) THDE 1 and (ii) THDE 2. We have reconstructed the Tsallis holographic quintessence model in the region $omega_{Lambda} > -1$ for the EoS parameter for both the cases. In addition, the quintessence phase of the THDE models is analyzed with swampland conjecture to describe the accelerated expansion of the Universe.
In present paper, we search the existence of dark energy scalar field models within in $f(R, T)$ gravity theory established by Harko et al. (Phys. Rev. D 84, 024020, 2011) in a flat FRW universe. The correspondence between scalar field models have been examined by employing new generalized dynamical cosmological term $ Lambda(t) $. In this regards, the best fit observational values of parameters from three distinct sets data are applied. To decide the solution to field equations, a scale factor $ a= left(sinh(beta t)right)^{1/n} $ has been considered, where $ beta$ & $n $ are constants. Here, we employ the recent ensues ($H_{0}=69.2$ and $q_{0}=-0.52)$ from (OHD+JLA) observation (Yu et al., Astrophys. J. 856, 3, 2018). Through the numerical estimation and graphical assessing of various cosmological parameters, it has been experienced that findings are comparable with kinematics and physical properties of universe and compatible with recent cosmological ensues. The dynamics and potentials of scalar fields are clarified in FRW scenario in the present model. Potentials reconstruction is highly reasonable and shows a periodic establishment and in agreement with latest observations.
The role of anisotropic components on the dark energy and the dynamics of the universe is investigated. An anisotropic dark energy fluid with different pressures along different spatial directions is assumed to incorporate the effect of anisotropy. One dimensional cosmic strings aligned along x-direction supplement some kind of anisotropy. Anisotropy in the dark energy pressure is found to evolve with cosmic expansion at least at late times. At an early phase, the anisotropic effect due to the cosmic strings substantially affect the dynamics of the accelerating universe.
Traversable wormholes, studied by Morris and Thorne cite{Morris1} in general relativity, are investigated in this research paper in $f(R,T)$ gravity by introducing a new form of non-linear $f(R,T)$ function. By using this novel function, the Einsteins field equations in $f(R,T)$ gravity are derived. To obtain the exact wormhole solutions, the relations $p_t=omegarho$ and $p_r=sinh(r)p_t$, where $rho$ is the energy density, $p_r$ is the radial pressure and $p_t$ is the tangential pressure, are used. Other than these relations, two forms of shape function defined in literature are used, and their suitability is examined by exploring the regions of validity of null, weak, strong and dominant energy conditions . Consequently, the radius of the throat or the spherical region, with satisfied energy conditions, is determined and the presence of exotic matter is minimized.
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