How the Universe postpones the evaporation and curtails the quantum spreading of black holes

TL;DR

This paper explores how the universe's conditions delay black hole evaporation and quantum spreading, allowing black holes to persist far longer than previously expected, especially outside galaxies and clusters.

Contribution

It demonstrates that cosmic energy influx delays black hole decay, extending their lifetime well beyond the Hubble horizon and previous theoretical estimates.

Findings

Black holes in galaxies are prevented from decaying until galaxy or cluster is cleared of dark matter.

Black holes outside galaxies are dragged beyond the Hubble horizon before significant decay occurs.

Black holes can remain localized and spread minimally over extremely long timescales, exceeding 10^{25} years.

Abstract

Black holes are expected to evaporate through the process of Hawking radiation. This process is expected to cause the uncertainty in a black hole's position to grow to $\sim M^2/M_{Pl}^3$ over the course of it's lifetime, even as its momentum spreads only by $\sim M_{Pl}$. For the black holes that have been observed, which have $M\geq M_\odot$, this greatly exceeds the Hubble volume. However, the decay of black holes and their quantum spreading, are delayed in the Universe while the influx of energy into the black holes exceeds their Hawking luminosity. We show that for these $M\geq M_\odot$ black holes, their decay outside galaxies and clusters is prevented far longer than it takes the black holes to be dragged well beyond the Hubble horizon, where their eventual decay occurs away from the prying eyes of any observer who has not hitched a ride with them. Meanwhile, black holes in an observer's galaxy or cluster are themselves prevented from decaying long past the extinction of the last stars, and at least until their galaxy/cluster is swept clean of dark matter, in $\gg 10^{25}$y. Even then, if the black holes become unbound they are dragged beyond the Hubble radius before undergoing significant decay; if not, they remain in bound orbits, spreading at most over a subvolume of the galaxy/cluster, and long localized by scatterings to much smaller volumes.