In the early universe, as it cooled after the Big Bang, defects could have formed, like cracks in ice. One such defect is a global monopole, a tiny clump of field where energy is trapped in a knot. When a monopole meets its antipode, they annihilate like a drop and a bubble, emitting waves — massless particles related to dark matter (called NG bosons).
The authors simulated the dance of these monopoles on a computer. The spectrum of emitted waves turned out not to be smeared out but concentrated in a peak at a scale comparable to the size of the visible universe. The same pattern was previously observed for cosmic strings — another type of defect.
The most interesting part begins if these waves acquire a tiny mass. Then they cease to be massless and turn into pseudo-NG bosons — heavy, slow, almost invisible. Such particles could constitute dark matter, which is thought to fill galaxies.
This creates a bridge between space defects and the mystery of dark matter. No need for the scorching furnaces of the early universe — monopoles themselves, by their disappearance, fill the cosmos with invisible substance. And if we ever catch a signal from such particles, it will remember the rhythm of that ancient dance.
Global monopoles have not been found yet, but if one were to pass through Earth, it would cause a tiny tremor in detectors, like the step of a giant.