Signatures of the Early Universe: Uncovering Cosmological Footprints

The post-inflationary epochs are critical for comprehending the early evolution of our Universe. This article delves into the cosmological signatures that shed light on these early epochs, particularly focusing on the generation of various phenomena such as matter production via inflaton oscillation and parametric resonance, primordial black holes, and gravitational waves. We review the theoretical frameworks that could produce these signatures and discuss the current observational constraints along with prospects for future detection. Furthermore, we explore the implications of such observations for our understanding of the physics of the early Universe.