V cosmological models in f ( R , T ) modified gravity with Λ ( T ) by using generation technique

摘要

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 , has been investigated for a specific choice of f ( R , T ) = f 1 ( R ) + f 2 ( T ) by generation of new solutions. Motivated by recent work of Pradhan et al. (2015) we have revisited the recent work of Ahmed and Pradhan (2014) by using a generation technique, it is shown that f ( R , T ) modified field equations are solvable for any arbitrary cosmic scale function. A class of new solutions for particular forms of cosmic scale functions have been investigated. In the present study we consider the cosmological constant Λ as a function of the trace of the stress energy-momentum-tensor, and dub such a model “ Λ ( T ) gravity” where we specified a certain form of Λ ( T ) . Such models may exhibit better equability with the cosmological observations. The cosmological constant Λ is found to be a positive decreasing function of time which is supported by results from recent supernovae Ia observations. Expressions for Hubble’s parameter in terms of redshift, luminosity distance redshift, distance modulus redshift and jerk parameter are derived and their significances are described in detail. The physical and geometric properties of the cosmological models are also discussed.