Primordial black holes and the black hole mass function in the hierarchical structure formation model

• Grant number: 25/17198-5
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: January 01, 2026
• End date: March 31, 2029
• Field of knowledge: Physical Sciences and Mathematics - Astronomy - Extragalactic Astrophysics
• Principal Investigator: Riccardo Sturani
• Grantee: Leandro Fontes Ferreira da Silva
• Host Institution: Instituto de Física Teórica (IFT). Universidade Estadual Paulista (UNESP). Campus de São Paulo. São Paulo , SP, Brazil
• Associated research grant: 22/06350-2 - Fundamental physics and LIGO, AP.ESP

Abstract

The rate of mergers of black holes of solar masses (up to 100 solar masses) detected by the LIGO, Virgo and Kagra observatories, together with the newly discovered population of high-redshift super- and ultra-massive black holes, present challenges to our current model of structure formation through gravitational collapse of primordial structures. The initial mass function of compact objects that could be the progenitors of these two populations of black holes is still unknown, and the evolution channels leading to such massive objects so early in cosmic time, and to the mergers that we observe in the local Universe, have not still been explored. These are wide fields of research, but the aspect we want to explore in this project is the intriguing parallel between the evolution of the black hole populations and structureformation in the Universe (i.e., the evolution of dark matter halos). In both cases the scenario is bottom-up: smaller structures merge to form larger ones, driving the mass function of both black holes and of halos to be increasingly top-heavy. Since it is widely believed that black hole mergers should occur inside dark matter halos,the two evolutionary scenarios must be intertwined. With this project we will explorehow large-scale cosmological structures constrain the rate of mergers, and how the evolution of the halo mass function is connected to the evolution of the black hole mass function. In particular, we plan to study the evolution of an initial population of primordial black holes that is abundant enough to constitute a non-negligible fraction, even though not dominant, of the dark matter. (AU)