Physicists explain why matter defeated antimatter

According to the standard cosmological model, after the Big Bang, matter and antimatter should have arisen in equal amounts and mutually annihilated, leaving only radiation. But the reality is that matter dominates the universe - and the reason for this is still unknown.

A new theoretical study conducted by Japanese scientists from Hiroshima University offers an original explanation for this asymmetry: the key role could play the so-called "cosmic knots" - energetically stable formations formed in the early universe.

As reported by Hiroshima University, the team led by Professor Muneto Nitta has shown for the first time that such knots can arise within realistic physical models that also explain the neutrino mass, the nature of dark matter and solve the so-called strong CP-problem - one of the strangest discrepancies between theory and experiment.

The researchers combined two important symmetries: the B-L (baryonic number minus lepton number) and the Pecchi-Quinn symmetry, which is related to the hypothetical axion particle. Together they allow us to predict the appearance in the early Universe of energetic structures - magnetic flows and vortices capable of weaving into stable knots.

During phase transitions after the Big Bang, when symmetries were "broken" and the structure of the Universe was rapidly changing, just such configurations - called nodal solitons - could arise. These "energy tangles" temporarily dominated the energy density, displacing radiation.

Later, scientists suggest, the knots "unravelled" through quantum tunnelling - a process in which particles pass energy barriers without classically overcoming them. When the knots decayed, heavy right-handed neutrinos were formed, decaying already with a slight bias towards matter. This asymmetric process could lead to a known predominance of matter over antimatter.

According to calculations, the temperature after the "unravelling" of the knots was about 100 gigaelectronvolts - just at the moment when the Universe still had reactions capable of "translating" neutrino asymmetry into baryonic, that is, material.

These knots could also leave behind unique traces in the form of gravitational waves - "background fluctuations" of spacetime that could be detected in the future by observatories such as LISA, DECIGO and Cosmic Explorer.

"Our model shows for the first time that knots, which Lord Kelvin speculated about back in the 19th century, can play a real physical role in the origin of matter," says Nitta.

The study is published in Physical Review Letters under the title Tying Knots in Particle Physics (2025).

Scientists hope that in the coming years it will be possible not only to improve theoretical models, but also to find observable signs that the universe has indeed gone through a knot-dominated epoch.