Using primordial black holes to form supermassive black holes in early universe nuclear star clusters

Primordial black holes (PBHs) are theorized to have formed in the early universe due to extreme density fluctuations in the first second after the Big Bang. They have since been one of the leading candidates for dark matter (Carr and Greene 2024). Supermassive black holes (SMBHs) on the order of ~10^6 - 10^8 Solar Masses have been observed to form in the universe much sooner than expected (within 200 million years after the Big Bang). Our objective was to show that PBHs in the mass range of 10^-11 - 10^-15 Solar Masses could be the cause of SMBHs and/or intermediate mass black holes at redshift z ≈ 10 in nuclear star clusters. We selected this specific mass range for the PBHs because it is the only one that, according to constraints from modern surveys and Hawking evaporation calculations, could account for all the dark matter in the universe. It has been shown that stellar mass black holes on the order of ~10 Solar Masses could be the seeds for these SMBHs (Kritos et al. 2024) by way of stellar mergers and Eddington-limited gas accretion. We tested with different initial values and found that, using a similar nuclear star cluster model, these seed black holes could have evolved into the same size with the same time constraint through star accretion, stellar mass black hole mergers, and primordial black hole mergers with limited or no gas present in the system. We then explore how different merger rates, final black hole size, and other conditions influence the final mass distribution of the seed black hole.