Symmetry Broken: Scientists Uncover First Evidence of Parity Violation in Universe

Tuesday - June 27 2023, 21:43 UTC - 1 year ago

The University of Florida astronomers have found the first evidence of a violation of symmetry at the moment of the universe's creation. This discovery has two primary consequences, first, that this symmetry violation imprinted itself onto the future galaxies during a period of extreme inflation in the universe's early stages, and second, it helps to explain why there is more matter than antimatter in the universe. It was conducted with a high level of statistical confidence, and answers the big questions of 'why is there something rather than nothing?'.

For generations, physicists were confident that the laws of physics were perfectly symmetric. Until they weren’t.

The notion of symmetry is neat and appealing, but it crumbles under the chaotic reality of our universe. In fact, from the 1960s onward, it has been necessary to introduce some form of broken symmetry to clarify why there’s more matter than antimatter in the universe – essentially explaining why anything exists at all.

But pinning down the source behind this existential symmetry violation, even finding proof of it, has been impossible.

Yet in a new paper, University of Florida astronomers have found the first evidence of this necessary violation of symmetry at the moment of creation. The UF scientists studied a whopping million trillion three-dimensional galactic quadruplets in the universe and discovered that the universe at one point preferred one set of shapes over their mirror images.

This idea, known as parity symmetry violation, points to an infinitesimal period in our universe’s history when the laws of physics were different than they are today, with enormous consequences for how the universe evolved.

The finding, established with a high level of statistical confidence, has two primary consequences. First, this parity violation could only have imprinted itself on the future galaxies during a period of extreme inflation in the earliest moments of the universe, confirming a central component of the Big Bang theory of the origin of the cosmos.

Parity violation would also help answer perhaps the most crucial question in cosmology: Why is there something instead of nothing? That’s because parity violation is required to explain why there is more matter than antimatter, an essential condition for galaxies, stars, planets, and life to form in the way they have.

"I’ve always been interested in 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 Zachary Slepian, a UF astronomy professor who supervised the new study. "This work addresses those big questions." .

Slepian worked with UF postdoctoral researcher and the study’s first author, Jiamin Hou, and Lawrence Berkeley National Laboratory physicist Robert Cahn to conduct the analysis. The trio recently published their findings in the journal Monthly Notices of the Royal Astronomical Society. The same researchers first proposed the idea of searching for parity violation using quadruplets of galaxies in a paper that was also recently published in Physical Review Letters.

Parity symmetry is the idea that physical laws shouldn’t prefer one shape over its mirror image. Scientists usually use the language of "handedness" to describe this trait, because our left and right hands are mirror images we are all familiar with. There is no way to rotate your left hand in three dimensions to make it look like your right hand, which means they are always distinguishable from one another.

Parity violation would mean that the universe does have a preference for either left- or right-handed shapes. To discover the universe’s handedness, Slepian’s lab was probing a million trillion randomly arranged quadruplets of galaxies using very advanced computational methods to develop an understanding of how round or stretched out the groups were when seen from different angles.