The symmetry in the laws of physics that regard matter and antimatter as perfect reflections of one another did not hold soon after the Big Bang, new evidence suggests. The work may offer an explanation for the troubling fact that, although the universe operates on symmetrical laws, antiparticles are far from equally abundant.
A universe that contained equal amounts of matter and antimatter would be one in which the two were constantly eliminating each other in bursts of energy. It is not a likely place for life to evolve, let alone make the long journey to beings capable of understanding the laws of physics. However, these laws, as we currently understand them, suggest that equal amounts of each substance should have been created with the universe.
We somehow escaped this fate, with matter overwhelmingly predominant. This observable fact means that somewhere along the line the universe was not perfectly symmetrical. Cosmologists have spent nearly 60 years looking for the point where symmetry failed. A new role in Monthly Notices of the Royal Astronomical Society (MNRAS) claims to reduce it to the so-called “inflationary era”.
The Doctor. Robert Cahn, Professor Zachary Slepian and Dr. Jiamin Hou proposed that the secret to finding where the symmetry was broken may lie in the distribution of galaxies. His reasoning was published in physical review lettersbut the most exciting news is that in the MNRAS paper, they claim to have found anomalies in the galactic distribution that they cannot explain any other way.
“A tetrahedron [triangular pyramid] it is the simplest shape that cannot be rotated in its three-dimensional (3D) mirror image,” note the authors at MNRAS. Any four galaxies (a quadruple) can be made to form the points of a tetrahedron. In an entirely symmetric universe, we would expect to see equal numbers of a tetrahedron’s orientation and its mirror image. If we see more examples of one than the other, it indicates a symmetry failure at the point where the irregularity of the universe’s mass arose.
Studying over a million bright red galaxies identified in two surveys the authors actually found an uneven distribution that implies a lack of symmetry present at this time. Exactly what this asymmetry was and where it went over the next 14 billion years remain unanswered questions. However, if the work is replicated, we can narrow our search.
“I’ve always been interested in the big questions about the universe. What is the beginning of the universe? What are the rules under which it evolves? Why is there something rather than nothing?” said Slepian in a statement. “This work addresses these big questions.”
Big questions are rarely answered easily, and analyzing such huge samples of galaxies was an extraordinarily complicated task. It was not simply a matter of finding organized clusters of four galaxies and categorizing each one as a right-handed or left-handed tetrahedron. Instead, the team needed a supercomputer to draw lines between each galaxy and three others to produce a tetrahedron, then do the same thing again with three others, and so on. Lines hundreds of millions of light-years long have been drawn to connect immensely distant galaxies in tetrahedrons much larger than the largest galaxy cluster.
“Eventually, we realized that we needed new mathematics,” Slepian said. The formulas meant that the computer didn’t need a substantial part of the age of the universe to analyze possible combinations. It was even able to rerun the calculations over and over again to verify they were correct.
The imbalance the team found in one sample of galaxies was highly unlikely to be by chance, and the other was even less plausible. Now, however, they plan to do the same thing again with larger galactic samples being produced by a more advanced generation of telescopes.
The only known existing symmetry violation is in the weak force, but as the papers note, its range is too short to explain deviations on a galactic scale, so the cause must be elsewhere.
Among other things, the work offers the potential to resolve the debate between inflationary and non-inflationary models of the early expansion of the universe. “Since parity violation can only be imprinted on the universe during inflation, if what we found is true, this provides irrefutable evidence for inflation,” Slepian said.
The evidence for asymmetry was published in the Monthly Notices of the Royal Astronomical Society.
The basis for the research was submitted in 2021 to Physical Review Letters, but has just been published.