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An f(R,T) Gravity Based FLRW Model and Observational Constraints

Anirudh PradhanGopikant GoswamiRita RaniAroonkumar Beesham
Oct 2022
We attempt to model a present time accelerating universe, in the framework ofFLRW space-time using field equations of f(R,T) gravity and taking $f(R,T) = R+ 2 \lambda T$, $\lambda$ being an arbitrary constant. For this, termscontaining $\lambda$ in the field equation are assumed as a source of energyproducing negative pressure. Our model is a novel one in the sense that the$\lambda$ parameter develops a fluid whose equation of state is parameterized.The model parameters, present values of density, Hubble and decelerationparameters are estimated statistically to arrive at physically viablecosmology. We consider three types of observational data set: $46$ Hubbleparameter data set, SNe Ia $715$ data sets of distance modulus and apparentmagnitude and 66 Pantheon data set (the latest compilation of SN Ia 40 binedplus 26 high redshift apparent magnitude $m_b$ data set in the redshift range$0.014 \leq z \leq 2.26 $. These data are compared with theoretical resultsthrough the $ \chi^2 $ statistical test. The universe model exhibits phasetransition from decelerating to accelerating one. We have calculated transionalred shifts and time for the data sets. Our estimated results for the presentvalues of various model parameters such Hubble , deceleration etc. are found asper expectations and surveys. We get a very interesting result from estimationsthat at present, the value of density $\rho_0$ is $\simeq 1.5 \rho_c $. Thecritical density is estimated as $\rho_c\simeq 1.88~ h_0^2~10^{-29}~gm/cm^3 $in the literature. The higher value of present density is attributed to thepresence of dark matter and dark energy in the universe. We have also examinedthe behaviour of pressure in our model. It is negative and is dominant overdensity $\simeq - 0.7 \rho_0$.