# Exploring strong-field deviations from general relativity via gravitational waves

## TL;DR

This paper discusses potential deviations from classical black holes in strong gravity regimes, proposing models and observational strategies using gravitational waves to detect quantum effects near black hole horizons.

## Contribution

It introduces simple models for quantum-modified black holes and explores how gravitational wave observations can test these deviations from general relativity.

## Key findings

- Models suggest possible near-horizon quantum effects
- Observational signatures depend on object properties
- Numerical simulations can assess detectability of deviations

## Abstract

Two new observational windows have been opened to strong gravitational physics: gravitational waves, and very long baseline interferometry. This suggests observational searches for new phenomena in this regime, and in particular for those necessary to make black hole evolution consistent with quantum mechanics. We describe possible features of "compact quantum objects" that replace classical black holes in a consistent quantum theory, and approaches to observational tests for these using gravitational waves. This is an example of a more general problem of finding consistent descriptions of deviations from general relativity, which can be tested via gravitational wave detection. Simple models for compact modifications to classical black holes are described via an effective stress tensor, possibly with an effective equation of state. A general discussion is given of possible observational signatures, and of their dependence on properties of the colliding objects. The possibility that departures from classical behavior are restricted to the near-horizon regime raises the question of whether these will be obscured in gravitational wave signals, due to their mutual interaction in a binary coalescence being deep in the mutual gravitational well. Numerical simulation with such simple models will be useful to clarify the sensitivity of gravitational wave observation to such highly compact departures from classical black holes.