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- We investigate a bounce realization in the framework of higher order curvature in f (R, T ) modified theory of gravity. We perform a detailed analysis of the cosmological parameters to explain the contraction phase, the bounce phase, and the expansion phase. Furthermore, we observe a violation of the null energy condition, instability of the model, and a singularity upon deceleration at the bouncing point, which are the supporting results for a bouncing cosmology. The equation of state parameter exhibits a ghost condensate behavior of the model near the bouncing point. Additionally, we discuss the stability of the model using linear perturbations in the Hubble parameter as well as the energy density.
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- We get an exact nonlinear electrodynamics (NED) charged black holes endowed with the perfect fluid dark matter (PFDM) in the AdS background-charged PFDM AdS black holes with additional parameter charge parameter q and PFDM parameter β apart from mass M. We investigate the extended phase space thermodynamics wherein we identify the black hole mass with the chemical enthalpy rather than internal energy. We analysed it in a canonical ensemble to probe the effects of the parameter β on the thermodynamic quantities. The behaviour of heat capacity reveals the existence of two secondorder phase transitions for decreasing β, the former occurring at increasing horizon radii xc1 and the latter at reduced values of xc2, where x is ratio of radial coordinate r and AdS length l (x = r/l). Whereas an analysis of Gibbs’ free energy confirms our black hole exhibits first order (small to large black hole) phase transition. The behaviour of the solution is consistent with Van der Waals fluid, which can also result from the P − V criticality describing the liquid/gas phase transition observed by the isotherms for temperatures less than the critical temperature. Thus, we show black holes can be understood from the viewpoint of chemistry, in terms of concepts such as Van der Waals fluids and can undergo phase transitions.
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- This article deals with a cosmological scenario in 𝑓(𝑅,𝑇) gravity for a flat FLRW model of the universe. We consider the 𝑓(𝑅,𝑇) function as 𝑓(𝑅) + 𝑓(𝑇) which starts with a quadratic correction of the geometric term f(R) having structure f(R) = R+αR2, and a linear matter term f(T) = 2λT. To achieve the solution of the gravitational field equations in the f (R,T) formalism, we take the form of a geometrical parameter, i.e. scale factor a(t) = sinh1 n (βt) (Chawla et al., 2013), where β and n are model parameters. An eternal acceleration can be predicted by the model for 0 < n < 1, while the cosmic transition from the early decelerated phase to the present accelerated epoch can be anticipated for n ≥ 1. The obtained model facilitates the formation of structure in the Universe according to the Jeans instability condition as our model transits from radiation dominated era to matter dominated era. We study the varying role of the equation of state parameter ω. We analyze our model by studying the behavior of the scalar field and discuss the energy conditions on our achieved solution. We examine the validity of our model via Jerk parameter, Om diagnostic, Velocity of sound and Statefinder diagnostic tools. We investigate the constraints on the model parameter n and H0 (Hubble constant) using some observational datasets: SNeIa dataset, H(z) (Hubble parameter) dataset, BAO (Baryon Acoustic Oscillation data) and their combinations as joint observational datasets H(z) + SNeIa and H(z) + SNeIa + BAO. It is testified that the present study is well consistent with these observations. We also perform some cosmological tests and a detailed discussion of the model.
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