$f(R)$-Cosmolgy from Early Universe Upto Future Cosmic Collapse and its Avoidance

英文摘要：

In the present model, a unified picture of cosmology from early inflation to late acceleration is obtained from $ f(R)-$ gravity with non-linear terms $ R^2 $ and $ R^5 $ of scalar curvature $R$. It is discussed that elementary particles and radiation are produced during early inflation. The emitted radiation thermalizes the universe to a very high temperature $ \sim 10^{18}{\rm GeV}$. The exit of the universe from inflationary phase is followed by deceleration due to radiation-dominance heralding the standard cosmology with background radiation having the initial temperature $ \sim 10^{18}{\rm GeV}$. It is found that dark matter is induced by curvature and baryonic matter is produced during inflation. Radiation-dominated phase is followed by deceleration due to matter-dominance. The curvature-induced phantom dark energy dominates at the red-shift $ z = 0.303 $ causing the late acceleration. It is found that the universe will collapse in future. Further, it is investigated that back-reaction of quantum particles produced near the collapse time can avoid cosmic collapse and the universe will escape to revival of the state of early universe.