Press-Schechter Formalism and The PBH Mass Distributions

Abstract: In this paper, we derive the primordial black hole (PBH) mass function using the Press-Schechter formalism, particularly using the excursion set approach, which is a powerful statistical method for obtaining the mass functions and modeling the formation of PBHs in the early universe by invoking the concepts like random walks. The excursion set formalism provides a framework for calculating the mass function by tracking the evolution of density fluctuations in the primordial universe and their subsequent collapse into PBHs uponcrossing critical barriers. By applying this theory, we compute the PBH mass function and explore its dependence on key parameters such as the peak mass,standard deviation, and initial PBH fraction. We also incorporate the effects of observational constraints, including microlensing and Cosmic Microwave Background (CMB) measurements, to place limits on the PBH population across different mass ranges. Our results offer important insights into the role of PBHs as potential dark matter candidates and their contribution to the overall matter content in the universe. The derived mass function provides a basis for further exploration of PBH formation, growth, and their possible detection through gravitational waves and other cosmological signatures.