Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8141212 | New Astronomy | 2019 | 21 Pages |
Abstract
General exact solutions of the Einstein's field equations by using conharmonically flat space with variable gravitational and cosmological “constants” for a spatially homogeneous and isotropic Friedmann-Robertson-Walker (FRW) model filled with perfect fluid has been obtained. To study the transit behaviour of Universe, we consider a law of variation of scale factor a(t)=(tket)1n which yields a time-dependent deceleration parameter (DP) q=â1+nk(k+t)2, comprising a class of models that depicts a transition of the universe from the early decelerated phase to the recent accelerating phase. We find that the time-dependent DP is reasonable for the present day Universe and give an appropriate description of the evolution of the universe. For n=0.27k, we obtain q0=â0.73 which is similar to observed value of DP at present epoch. It is also observed that for nâ¯â¥â¯2 and k=1, we obtain a class of transit models of the universe from early decelerating to present accelerating phase. For k=0, the universe has non-singular origin. In these models, we arrive at the decision that, from the structure of the field equations, the behaviour of Î and G are related. Taking into consideration the observational data, we conclude that the Î behaves as a positive decreasing function of time whereas G is increasing and tend to a constant value at the late time. Our derived model is in good agreement with ÎCDM model. Some physical and geometric properties of the models are also discussed.
Related Topics
Physical Sciences and Engineering
Physics and Astronomy
Astronomy and Astrophysics
Authors
Manish Goyal, Rishi Kumar Tiwari, Anirudh Pradhan,