Observational evidence for cosmological coupling of black holes and its implications for an astrophysical source of dark energy

TL;DR

This paper presents observational evidence that black holes grow in a way coupled to the universe's expansion, suggesting they could be the astrophysical source of dark energy and explaining cosmic acceleration.

Contribution

It provides the first observational evidence for cosmological coupling of black hole mass growth, proposing black holes as the origin of dark energy and cosmic acceleration.

Findings

Black holes show mass growth consistent with cosmological coupling.

Zero coupling is statistically excluded at 99.98% confidence.

Black hole contribution matches observed dark energy density.

Abstract

Observations have found black holes spanning ten orders of magnitude in mass across most of cosmic history. The Kerr black hole solution is however provisional as its behavior at infinity is incompatible with an expanding universe. Black hole models with realistic behavior at infinity predict that the gravitating mass of a black hole can increase with the expansion of the universe independently of accretion or mergers, in a manner that depends on the black hole's interior solution. We test this prediction by considering the growth of supermassive black holes in elliptical galaxies over $0<z\lesssim2.5$. We find evidence for cosmologically coupled mass growth among these black holes, with zero cosmological coupling excluded at 99.98% confidence. The redshift dependence of the mass growth implies that, at $z\lesssim7$, black holes contribute an effectively constant cosmological energy density to Friedmann's equations. The continuity equation then requires that black holes contribute cosmologically as vacuum energy. We further show that black hole production from the cosmic star formation history gives the value of $\Omega_{\Lambda}$ measured by Planck while being consistent with constraints from massive compact halo objects. We thus propose that stellar remnant black holes are the astrophysical origin of dark energy, explaining the onset of accelerating expansion at $z \sim 0.7$.