# Making light of gravitational-waves

## TL;DR

This paper explores the potential for detecting gravitational waves via their conversion into photons in magnetic fields, proposing that a lunar telescope array could observe a neutron star merger background, providing insights into quantum gravity effects.

## Contribution

It introduces a novel approach using numerical simulations to assess the detectability of gravitational wave backgrounds through photon conversion with lunar telescopes.

## Key findings

- A lunar array with 1000 elements could detect a neutron star merger background under certain conditions.
- Detection likelihood depends on the gravitational wave spectrum damping and background subtraction.
- Non-detection could set competitive bounds on quantum gravitational energy scales.

## Abstract

Mixing between photons and low-mass bosons is well considered in the literature. The particular case of interest here is with hypothetical gravitons, as we are concerned with the direct conversion of gravitons into photons in the presence of an external magnetic field. We examine whether such a process could produce direct low-frequency radio counterparts to gravitational-wave events. Our work differs from previous work in the literature in that we use the results of numerical simulations to demonstrate that, although a single such event may be undetectable without at least 100000 dipoles, an unresolved gravitational wave background from neutron star mergers could be potentially detectable with a lunar telescope composed of 1000 elements. This is provided the gravitational wave spectrum only experiences exponential damping above 80 kHz, a full order of magnitude above the limit achieved by present simulation results. In addition, the extrapolation cannot have a power-law slope < -2 (for 100 hours of observation time) and background and foregrounds must be effectively subtracted to obtain the signal. This does not make detection impossible, but suggests it may be unlikely. Furthermore, assuming a potentially detectable spectral scenario we show that, for the case when no detection is made by a lunar array, a lower bound, competitive with those from Lorentz-invariance violation, may be placed on the energy-scale of quantum gravitational effects. The SKA is shown to have very limited prospects for the detection of either a single merger or a background.