Hints of dark matter possibly found in gravitational wave signals by CP3 researcher

Gravitational waves from merging black holes are opening a new avenue for exploring fundamental physics. These signals can reveal whether black holes are surrounded by previously unknown forms of matter that would otherwise be extremely difficult to detect.

In this research, Dr Soumen Roy, CP3 postdoctoral researcher, and collaborators have investigated the possibility that black hole binaries are embedded in ultralight scalar particles, which are among the most well-motivated candidates for dark matter. If present, these particles can influence the motion of the black holes during their inspiral and leave subtle but measurable signatures in the emitted gravitational-wave signal.

To test this idea, they developed a new gravitational-wave model that includes the effects of scalar-field environments around black hole binaries. The model was validated against numerical relativity simulations and then applied to data from the first three observing runs of the LIGO–Virgo–KAGRA collaboration.

This analysis sets the first physically meaningful bounds on scalar-field environments around compact binaries. While most observed events remain consistent with the standard vacuum picture around black holes, one event in particular, GW190728, shows tentative evidence for such an environment when physically motivated assumptions are included. If future gravitational wave observations support this interpretation, it could point to the existence of a new ultralight particle with a mass around 10^{-12} electronvolts.

More broadly, this work shows that gravitational-wave observations can probe scalar-field environments around merging black holes, opening a new avenue for testing dark matter and other new physics in the strong-gravity regime.