A scientist thinks he has found a solution to one of the oldest problems in the universe

A scientist thinks he has found a solution to one of the oldest problems in the universe

This is one of the oldest problems in the universe: since matter and antimatter annihilate on contact, and both forms of matter existed at the time of the big bang, why is there a universe composed mostly of matter rather than nothing at all? Where did all the antimatter go?

“That our current universe is dominated by matter remains one of the most puzzling and ancient mysteries of modern physics,” said Yanou Cui, a Riverside professor of physics and astronomy at the University of California, in a statement shared this week. “A subtle imbalance or asymmetry between matter and antimatter in the early universe is necessary to achieve the current dominance of matter, but cannot be achieved within the known framework of fundamental physics.”

There are theories that could answer this question, but they are extremely difficult to test using laboratory experiments. Now, in a new article published Thursday in the journal Physical examination lettersDr. Cui and his co-author, Zhong-Zhi Xianyu, an assistant professor of physics at Tsinghua University, China, say they may have found a way to use the afterglow of the big bang itself to conduct the experiment.

The theory that Drs. Cui and Zhong-Zh wanted to explore is known as leptogenesis, a process involving the decay of particles that could have led to the asymmetry between matter and antimatter in the early universe. In other words, an asymmetry in certain types of elementary particles in the very first moments of the cosmos could have developed over time and through other particle interactions in the asymmetry between matter and antimatter that made the universe as we know it – and life – possible.

“Leptogenesis is one of the most compelling mechanisms generating matter-antimatter asymmetry,” Dr. Cui said in a statement. “This is a new fundamental particle, the right-handed neutrino.”

But, Dr Cui added, generating a right-handed neutrino would require far more energy than can be generated in particle colliders on Earth.

“Testing for leptogenesis is nearly impossible because the mass of the right-handed neutrino is typically several orders of magnitude beyond the reach of the highest-energy collider ever built, the Large Hadron Collider,” she said.

The idea of ​​Dr. Cui and his co-authors was that scientists might not need to build a more powerful particle collider, because the very conditions they would like to create in such an experiment already existed in some parts of the early universe. The inflationary period, an era of exponential expansion of time and space itself that lasted only fractions of a second after the big bang, ….

“Cosmic inflation provided a high-energy environment, allowing the production of new heavy particles as well as their interactions,” Dr Cui said. “The inflationary universe behaved like a cosmological collider, except the energy was up to 10 billion times larger than any man-made collider.”

Moreover, the results of these natural cosmic collider experiments can be preserved today in the distribution of galaxies, as well as the cosmic microwave background, the afterglow of the big bang from which astrophysicists have derived much of their current understanding of the evolution of the cosmos. .

“Specifically, we demonstrate that the conditions essential for the generation of asymmetry, including the interactions and masses of the right-handed neutrino, which is the key player here, can leave distinctive imprints in statistics of the spatial distribution of galaxies. or the cosmic microwave background and can be accurately measured,” Dr Cui said, although such measurements, she added, remain to be done. “Astrophysical observations anticipated in the coming years can potentially detect such signals and unravel the cosmic origin of matter.”

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