Signals from the Early Universe: Black Holes, Gravitational Waves and Particle Physics

TL;DR

This thesis explores primordial black holes, their formation, evolution, and gravitational wave signatures, aiming to understand their role in dark matter and early universe physics, with implications for current and future gravitational wave observations.

Contribution

It provides a comprehensive analysis of primordial black holes from formation to detection, integrating their astrophysical properties with early universe particle physics and gravitational wave signals.

Findings

PBHs could constitute a fraction of dark matter.

GW signals from PBH coalescence are detectable by current and future observatories.

The study links black hole physics with early universe phenomena.

Abstract

We dedicate this thesis to the study of signatures coming from the primordial epochs of the universe. We will focus in particular on Primordial Black Holes (PBHs), which may be formed from perturbations generated during inflation and might comprise a fraction of the dark matter in the universe. In the first part of the thesis, we will address the PBH properties at the time of formation, that are their masses, spins and abundance, and investigate the generation of Gravitational Wave (GW) signals during their production. In the second part, we will describe the PBHs evolution across the cosmic history due to their assemble in binaries, phases of baryonic mass accretion and clustering effects. We will then discuss GW signatures coming from their coalescence, compare these predictions with present GW data detected by the LIGO/Virgo Collaboration (LVC) and assess the role of future GW experiments like 3G detectors and LISA in discovering these objects. Finally, in the third part, we will investigate some aspects of the interplay between black holes and fundamental physics in the early universe, focusing on the role of GWs to shed light on their properties.