Abstract
Primordial black holes (PBHs) offer a unique window into the physics of the early universe, potentially linking quantum fluctuations during inflation to astrophysical phenomena observable today. In this pedagogical talk, I will introduce the basic mechanisms by which PBHs may have formed from enhanced inflationary scalar perturbations in the early universe. Beginning with a review of inflationary dynamics, I will explain how quantum fluctuations in the inflaton field can seed regions of overdensity. Under certain conditions, these overdense regions re-enter the horizon after inflation and undergo gravitational collapse, giving rise to black holes with masses ranging from sub-atomic scales to many solar masses. I will discuss the criteria for collapse, the role of the equation of state, and the mass spectrum of the resulting PBHs. Finally, I will explore the possible roles PBHs might play in cosmic evolution—including their relevance to dark matter, structure formation, and gravitational wave backgrounds—highlighting how their study connects fundamental theory with cosmological and astrophysical observations.