In general relativity, black holes are most commonly described by stationary geometries, such as Schwarzschild and Kerr spacetimes. These represent isolated objects in asymptotically flat backgrounds. These solutions, however, neglect the effects of cosmological expansion, which could be significant for black holes formed in the early universe. Dynamical black hole spacetimes coupled to cosmological backgrounds provide a framework through which this issue can be addressed. In this talk, I discuss how black holes evolve during the inflationary epoch, assuming they are dynamically coupled to the cosmological expansion via a generalised McVittie geometry. The combined effects of cosmological coupling, Hawking evaporation and radiation accretion during the subsequent cosmic eras (inflation, radiation, matter and dark energy) are analysed. Requiring the black hole event horizon to remain smaller than the particle horizon at all times yields an upper bound on the mass parameter. Radiation accretion during the radiation era further constrains the parameter space to prevent runaway growth, while Hawking evaporation sets a lower bound on the initial mass to ensure survival through inflation. These findings suggest that only black holes formed within a specific initial mass range during inflation can persist to the present day, achieving a maximum mass of ~ 0.001043 Solar masses.

Location: Spořilov, seminar room

Supermassive black holes (SMBH) that are found in the centres of most galaxies comply with scaling relationships that imply hand-in-hand growth of the SMBH and its galaxy bulge, which in turn implies that the SMBHs play a significant role in regulating galaxy assembly. SMBHs grow via coalescence as a consequence of their host galaxies merging or due to accretion. Our current broad understanding is that the SMBHs influence star formation via the consequences of accretion, which enables them to impact their environments out to spatial scales that are well beyond their gravitational sphere of influence. However, the exact mechanisms and the circumstances under which positive and negative feedback dominate remain elusive. I will describe a multi-frequency investigation of the imprints if any at very nearby redshifts of this feedback between the accretion around the SMBH and star formation in the host galaxy.

Location: Room ASU Spořilov and via Zoom