Exploring Gravitational Waves from Primordial Black Holes in Extra Dimensions
Recent research has explored the implications of gravitational waves generated from the evaporation of primordial black holes, particularly in the context of theories that incorporate large extra dimensions. The study, titled "Gravitational Waves from Primordial Black Hole Evaporation with Large Extra Dimensions," authored by Aurora Ireland, Stefano Profumo, and Jordan Scharnhorst, was submitted to arXiv on December 13, 2023, and revised on August 23, 2024.
The research indicates that the gravitational wave spectra from black hole evaporation typically peak at frequencies corresponding to the Hawking temperature. This phenomenon results in ultra-high frequency signals for primordial black holes that evaporated in the early universe. However, the authors propose that by considering small black holes within frameworks that allow for large extra dimensions, it is possible to significantly lower the peak frequency. This is due to the fact that the true bulk Planck scale can be much smaller than the effective Planck scale used in conventional theories.
The study focuses on the emission of brane-localized gravitons during the Hawking evaporation of ultra-light primordial black holes. The authors aim to compute the contribution of these emissions to the stochastic gravitational wave background. To achieve this, they calculate greybody factors for particles of various spins emitted both on the brane and in the bulk, assuming that most emissions occur during the Schwarzschild phase of black hole evolution.
The findings suggest that for optimal parameter choices, the peak frequency of the gravitational waves could plateau in the sub-MHz range. This frequency range is significant as it falls within the detection capabilities of planned high-frequency gravitational wave detectors, making these primordial black holes a target for future observations. The implications of this research could enhance our understanding of gravitational waves and their sources, potentially leading to new insights in cosmology and high-energy physics.
For further details, the paper can be accessed at arXiv:2312.08508.