Black Holes, Mergers, and the Entropy Budget of the Universe

TL;DR

This paper discusses how the entropy generated during black hole formation and mergers impacts the universe's entropy budget, suggesting that supermassive black holes contain most of the universe's entropy and can constrain black hole formation processes.

Contribution

It introduces a novel approach to constraining supermassive black hole formation and mergers based on entropy considerations, offering potential tests for numerical simulations.

Findings

Supermassive black holes hold most of the universe's entropy.

Black hole formation and mergers significantly influence the universe's entropy budget.

Entropy considerations can constrain models of black hole growth.

Abstract

Vast amounts of entropy are produced in black hole formation, and the amount of entropy stored in supermassive black holes at the centers of galaxies is now much greater than the entropy free in the rest of the universe. Either mergers involved in forming supermassive black holes are rare,or the holes must be very efficient at capturing nearly all the entropy generated in the process. We argue that this information can be used to constrain supermassive black hole production, and may eventually provide a check on numerical results for mergers involving black holes.