Bianchi Type-$V$ cosmology in $f(R,T)$ gravity with $Λ(T)$

Abstract: A new class of cosmological models in $f(R, T)$ modified theories of gravity proposed by Harko et al. (2011), where the gravitational Lagrangian is given by an arbitrary function of Ricci scalar $R$ and the trace of the stress-energy tensor $T$, have been investigated for a specific choice of $f(R, T) = f_{1}(R) + f_{2}(T)$ by considering time dependent deceleration parameter. The concept of time dependent deceleration parameter (DP) with some proper assumptions yield the average scale factor $a(t) = \sinh^{\frac{1}{n}}(\alpha t)$, where $n$ and $\alpha$ are positive constants. For $0 < n \leq 1$, this generates a class of accelerating models while for $n > 1$, the models of universe exhibit phase transition from early decelerating phase to present accelerating phase which is in good agreement with the results from recent astrophysical observations. Our intention is to reconstruct $f(R,T)$ models inspired by this special law for the deceleration parameter in connection with the theories of modified gravity. In the present study we consider the cosmological constant $\Lambda$ as a function of the trace of the stress energy-momentum-tensor, and dub such a model "$\Lambda(T)$ gravity" where we have specified a certain form of $\Lambda(T)$. Such models may display better uniformity with the cosmological observations. The statefinder diagnostic pair ${r,s}$ parameter has been embraced to characterize different phases of the universe. We also discuss the physical consequences of the derived models.