Abstract

Over the past ten years, observational evidence has continued to mount that astrophysical black holes grow too quickly or are more massive than easily explained by physical processes such as merger and accretion. With the advent of gravitational wave astronomy, this evidence now spans all observational channels, over ten orders of magnitude in mass, and over cosmological timescales. The simplest black hole model, Kerr, cannot be applied over cosmological timescales because it has non-cosmological boundary conditions. Aspects of non-singular and horizon-free black hole models in General Relativity suggest dynamics on cosmological timescales that can help to ease these observational tensions. We review recent formal advances in General Relativity that permit investigation of candidate black hole models through their possible cosmological interactions, and present the first observational evidence for cosmologically coupled mass growth in the supermassive black holes of quiescent elliptical galaxies. The measured growth is consistent with a vacuum energy equation of state for astrophysical black hole contributions in aggregate, leading to the striking prediction that astrophysical black holes may well be the material source that drives accelerated late-time expansion.