# Probing quantum gravity using high-energy astrophysics

## TL;DR

This paper investigates how high-energy astrophysical signals from hypothetical Planck stars could test quantum loop gravity theories, using cosmic background observations to place empirical constraints on such models.

## Contribution

It introduces a method to constrain quantum loop gravity effects by analyzing high-frequency signals from primordial black hole explosions across cosmic history.

## Key findings

- Stringent constraints on energy release from Planck star explosions
- High-energy signals unlikely to produce gamma-ray bursts as previously speculated
- Empirical limits placed on quantum loop gravity models using cosmic background data

## Abstract

The events observed by LIGO indicate the existence of a large population of intermediate mass black holes. This unexpected result lead to a resurgence in the interest in theories of the formation of primordial black holes with several studies showing that broad mass distributions can evade or satisfy the stringent constraints on monochromatic populations. If such large populations exist they provide the perfect test-bed for theories beyond the standard model of physics that modify black hole evolution. The case we studied is that of "Planck stars", a hypothetical modification of the black hole evolution where it explodes via quantum loop gravity motivated tunnelling. We determine what the high-frequency background signal of such objects exploding over the whole of cosmic history would look like for various black hole populations to place actual empirical constraints on quantum loop gravity via comparison to observed isotropic background signals at the same frequencies. We find that stringent constraints heavily restrict the amount of energy released via the high-energy channel, thereby casting doubt on whether or not the high-energy signal could result in gamma-ray bursts as speculated in the literature.