Abstract
The current paper is concerned with new cosmological models of the existence of a perfect fluid source in f(R) and f(R,T)-gravity. A varying polynomial deceleration parameter is utilized. Previously, such models were obtained without any restrictions on the parameter of the field equation. The dynamical features of the model, including the behavior of the state parameter, are examined. The behavior of the energy, pressure, and jerk parameters for the model are also discussed. Additionally, this is happening with a wide range of other parameters. These suggested cosmological models correspond to astronomical observations to some extent as an expectation of what will happen after the Big Rip. The first model covers a linearly varying deceleration parameter model. Furthermore, it covers the law of Berman. The second model is represented as a Rip-Crunch model. A varying polynomial deceleration parameter produced multiple cosmological models. These models may be utilized in explaining the evolution of the Universe.