Cosmic Evolution with Early and Late Acceleration Inspired by the Dual Nature of the Ricci Scalar Curvature

In the present paper, a cosmological scenario is proposed in which dark energy emerges spontaneously from modified gravity. In this scenario, the universe inflates for ~10^-37 s in the beginning and the late universe accelerates after 8.58 Gyrs. During the long intermediate period, the universe decelerates driven by radiation and subsequently by matter. The gravitational dark energy that emerges in this model mimics quintessence and its density falls by 115 orders from 2.18 × 10⁶⁸ GeV⁴ initially to its current value 2.19 × 10^-47 GeV⁴.