Speaker
Description
Black holes formed in the early Universe (primordial black holes, PBHs) may simultaneously explain several astrophysical anomalies. These include, for example, the existence of supermassive black holes in the young Universe ($z>6$, Mazzucchelli C. et al., (2017, ApJ)) and black holes with masses of $∼100\ M_\odot$ detected by gravitational-wave observatories (LVK Scientific Collaboration et al. 2025) that fall into the “forbidden” mass gap for remnants of stellar collapse Abbott R. et al. (2020b, Phys. Rev. Lett.). PBHs may also contribute a fraction of the dark matter (DM). According to P. Mroz et al. (2024, Nature), constraints derived from microlensing, astrophysical, and cosmological data suggest that compact objects in the mass ranges $~10^{-4}$`to $6\ M_\odot$ and $~10^{-5}$ to $860\ M_\odot$ can constitute no more than $1\%$ and $10\%$ of DM, respectively. However, these limits are model-dependent and typically neglect both the broad mass distribution predicted for PBHs and their possible clustering. Recent work Y. Eroshenko et al., Symmetry 15, 637 (2023) indicates that PBHs in the galactic halo may form dense clusters. If true, this clustering would significantly reduce the probability of microlensing of distant stars, effectively invalidating existing constraints. We present results of numerical simulation of dense PBH clusters evolution within the Galactic potential. The resulting PBH cluster models can be used to identify such objects through their microlensing signatures.
