An f (R, T) gravity based FLRW model and observational constraints

We attempt to construct a Friedmann-Lemaitre-Robertson-Walker (FLRW) cosmological model in f (R , T) gravity which exhibits a phase transition from deceleration to acceleration at present. We take f (R , T) = R + 2 lambda T , lambda being an arbitrary constant. In our model, the lambda parameter develops a negative pressure in the universe whose Equation of state is parameterized. The present values of model parameters such as density, Hubble, deceleration, Equation of state, and lambda are estimated statistically by using the Chi-Square test. For this, we have used three different types of observational data sets: the 46 Hubble parameter data set, the SNeIa 715 data sets of distance modulus, and the 66 Pantheon data set (the latest compilation of SNeIa 40 bined plus 26 high red shift apparent magnitude mb data set in the red shift ranges from 0.014 <= z <= 2.26). We have calculated the transitional red shift and time. The estimated results for the present values of various model parameters are found as per expectations and surveys. Interestingly, we get the present value of the density rho(0) similar or equal to 1.5 rho c. The critical density is estimated as rho(c) similar or equal to 1.88 h(0)(2) 10(-29) gm/cm(3) in the literature. The higher value of the present density is attributed to the presence of some additional energies in the universe apart from baryon energy. We have examined the behavior of the pressure in our model. It is negative and produces acceleration in the universe. Its present value is obtained as p(0) similar or equal to -0.7 rho(0). (c) 2023 Elsevier B.V. All rights reserved.