Discovering new forces with gravitational waves from supermassive black holes

Understand

Supermassive black hole binary mergers generate a stochastic gravitational wave background detectable by pulsar timing arrays.

• While the amplitude of this background is subject to significant uncertainties, the frequency dependence is a robust prediction of general relativity.
• We show that the effects of new forces beyond the Standard Model can modify this prediction and introduce unique features into the spectral shape.
• In particular, we consider the possibility that black holes in binaries are charged under a new long-range force, and we find that pulsar timing arrays are capable of robustly detecting such forces.