LRS Bianchi-I transit universe with periodic varying q in f(R,T) gravity

We have investigated the cosmic transit behavior of LRS Bianchi-I universe in modified [Formula: see text] gravity theory whose functional form is taken as [Formula: see text], where [Formula: see text] is Ricci scalar and [Formula: see text] is the energy–momentum tensor. Subjecting the deceleration parameter [Formula: see text] to periodic variations as [Formula: see text], where [Formula: see text], the oscillatory behavior of EoS parameter and violation of energy–momentum conservation in the wide range of parameters have been observed. Hubble parameter oscillates but remains positive which signify the alternate decelerating and accelerating expansion of universe with no singularity.

Toy Models of Universe with an Effective VaryingΛ-Term in Lyra Manifold

Research on the accelerated expansion of our Universe captures a lot of attention. The dark energy (DE) is a way to explain it. In this paper we will consider scalar field quintessence DE withωDE>-1EoS, where the dynamics of the DE models related to the dynamics of the scalar field. We are interested in the study of the behavior of the Universe in the presence of interacting quintessence DE models in Lyra manifold with a varyingΛt. In a considered framework we also would like to propose a new form forΛt. We found that the models correspond to the transit Universe, which will enter the accelerated expansion phase and will remain there with a constant deceleration parameterq. We found also that theΛtis a decreasing function which takes a small positive value withΩm≠0andΩQ→constdominatingΩmin the old Universe. Observational constraints are applied and causality issue viaCS2is discussed as a possible way to either reject or accept the models.