Japanese Physicists Revive 150-Year-Old Theory to Explain Universe’s Matter Asymmetry

A team of Japanese physicists has revived a 150-year-old hypothesis proposed by Lord Kelvin to address a fundamental question in cosmology: why does the universe consist predominantly of matter while antimatter is scarce? In a recent study, researchers from Hiroshima University suggest that the concept of “cosmic knots”—topological structures formed in spacetime—may provide insight into this enduring mystery.

The original idea, introduced in 1867, envisioned atoms as complex knots within the aether. While this notion was soon discredited, modern physicists are exploring its potential implications. The new research posits that these cosmic knots could have emerged during the universe’s formative moments, leading to conditions that favored the production of matter over antimatter.

Understanding the matter-antimatter asymmetry is crucial, as the Big Bang theory indicates that equal amounts of matter and antimatter should have been created. Instead, observations show a significant imbalance; for every billion matter-antimatter pairs, only one matter particle survives. This discrepancy raises profound questions about the nature of the universe and our existence within it.

Muneto Nitta, a professor at Hiroshima University and the study’s corresponding author, emphasized the importance of this question. He stated, “This study addresses one of the most fundamental mysteries in physics: why our universe is made of matter and not antimatter. This question is important because it touches directly on why stars, galaxies, and we ourselves exist at all.”

The researchers propose that the phenomenon known as baryogenesis may hold the key to understanding this asymmetry. By combining two significant theoretical frameworks—Baryon Number Minus Lepton Number (B-L) symmetry and Peccei–Quinn (PQ) symmetry—the team suggests that cosmic knots could have formed naturally in the early universe, resulting in a surplus of matter. The PQ symmetry also introduces axions, a leading candidate for dark matter, while the B-L symmetry helps explain the behavior of neutrinos, often referred to as “ghost particles” due to their elusive nature.

Cosmic Strings and Their Implications

As the early universe cooled, phase transitions likely produced cosmic strings, which are hypothetical defects in spacetime. Nitta’s team theorizes that a combination of flux-carrying B-L strings and superfluid-like PQ vortices could lead to the formation of stable knot solitons.

“Nobody had studied these two symmetries at the same time. Putting them together revealed a stable knot,” Nitta explained. Eventually, these knots would decay through quantum tunneling, resulting in the creation of heavy right-handed neutrinos, which ultimately contributed to the greater abundance of matter compared to antimatter.

The team’s calculations indicate that the mass of these heavy neutrinos and the energy released from the collapse of the knots could have caused the universe to reheat to approximately 100 GeV. This specific energy threshold is critical for the sustained formation of matter in the universe.

Furthermore, the researchers propose that the process involved in the formation and decay of these cosmic knots may have altered the universe’s “gravitational wave chorus,” shifting it toward higher frequencies. This transformation could be detectable by future observatories, including the Laser Interferometer Space Antenna (LISA) in Europe, Cosmic Explorer in the United States, and the Deci-hertz Interferometer Gravitational-wave Observatory (DECIGO) in Japan.

The implications of this research extend beyond theoretical physics. Understanding the mechanisms that led to the dominance of matter in the universe could reshape our comprehension of cosmic evolution and the fundamental laws governing it. As scientists continue to explore these cosmic knots, they may uncover new insights that further illuminate the mysteries surrounding our existence in this vast universe.