Could cosmic defects masquerade as black hole mergers in gravitational waves?

Using data from two mysterious gravitational-wave events (GW190521 and GW231123), researchers tested whether cosmic domain walls—topological defects in spacetime from dark matter—could mimic black hole mergers. While standard black hole explanations remain favored, the domain wall fits were surprisingly close, and a joint analysis showed both events could arise from the same underlying scalar field. Critically, fake domain wall signals injected into data were routinely misidentified as high-spin black holes, exposing a degeneracy that could let genuine dark matter signals hide in plain sight.