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Register a new userAnisotropic cosmological reconstruction in $f(R,T)$ gravity
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Added by
Sunil Kumar Tripathy Dr.
Publication date
2017
fields
Physics
and research's language is
English
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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.
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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.
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.
We study strange stars in the framework of $fleft(R,mathcal{T}right)$ theory of gravity where the strange quark matter distribution inside the stellar system is governed by the phenomenological MIT Bag model equation of state (EOS). 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 $fleft(R,mathcal{T}right)$ gravity and have studied in detail the dependence of the different physical parameters due to the chosen different values of $chi$. 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 $fleft(R,mathcal{T}right)$ gravity, on the anisotropic compact stellar system. It is interesting to note that as the values of $chi$ 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 $fleft(R,mathcal{T}right)$ gravity is a suitable theory to explain massive stellar systems like recent magnetars, massive pulsars and super-Chandrasekhar stars, which can not be explained in the framework of GR. However, for $chi=0$ the standard results of Einsteinian gravity are retrieved.
The $f(R,T)$ theory of gravitation is an extended theory of gravitation in which the gravitational action contains both the Ricci scalar $R$ and the trace of energy momentum tensor $T$ and hence the cosmological models based on $f(R,T)$ gravity are eligible to describing late time acceleration of present universe. In this paper, we investigate an accelerating model of flat universe with linearly varying deceleration parameter (LVDP). We apply the linearly time varying law for deceleration parameters that generates a model of transitioning universe from early decelerating phase to current accelerating phase. We carry out the state-finder and Om(z) analysis, and obtain that LVDP model have consistency with astrophysical observations. We also discuss profoundly the violation of energy-momentum conservation law in $f(R,T)$ gravity and dynamical behavior of the model.
In the present work, a new form of the logarithmic shape function is proposed for the linear $f(R,T)$ gravity, $f(R,T)=R+2lambda T$ where $lambda$ is an arbitrary coupling constant, in wormhole geometry. The desired logarithmic shape function accomplishes all necessary conditions for traversable and asymptotically flat wormholes. The obtained wormhole solutions are analyzed from the energy conditions for different values of $lambda$. It has been observed that our proposed shape function for the linear form of $f(R,T)$ gravity, represents the existence of exotic matter and non-exotic matter. Moreover, for $lambda=0$ i.e. for the general relativity case, the existence of exotic matter for the wormhole geometry has been confirmed. Further, the behaviour of the radial state parameter $omega_{r}$, the tangential state parameter $omega_{t}$ and the anisotropy parameter $triangle$ describing the geometry of the universe, has been presented for different values of $lambda$ chosen in $[-100,100]$.
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