Scientists think they’ve found a solution to one of the universe’s oldest problems

Scientists think they've found a solution to one of the universe's oldest problems
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It is one of the oldest problems in the universe: From affair Y antimatter annihilate each other on contact, and both forms of matter existed at the time of big Bang, why is there a universe made mostly of matter instead of nothing at all? Where did all the antimatter go?

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

There are theories that could answer that question, but they are extremely difficult to test using laboratory experiments now on a new paper published Thursday in the magazine Physical Review LettersDr. Cui and her co-author, Zhong-Zhi Xianyu, an assistant professor of physics at Tsinghua University, China, explain that they may have found a way to avoid using the afterglow of the Big Bang to run 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 asymmetry between matter and antimatter in the early universe. An asymmetry in certain types of elementary particles in the early days of the cosmos, in other words, could have grown over time and through more particle interactions into the asymmetry between matter and antimatter that made the universe as we know it. and life. possible.

“Leptogenesis is among the most convincing mechanisms that generate the asymmetry between matter and antimatter,” 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 much more energy than can be generated in particle colliders on Earth.

“Testing leptogenesis is almost impossible because the mass of the right-handed neutrino is typically many orders of magnitude beyond the range of the highest-energy collider ever built, the Large Hadron Collider,” he said.

The idea of ​​Dr. Cui and her co-authors was that scientists may 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 parts of the early universe. The inflationary period, an epoch of exponential expansion of time and space itself that lasted only fractions of a second after the big bang,…

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

Furthermore, the results of those experiments with natural cosmological colliders may be preserved today in the distribution of galaxiesas 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 show that the essential conditions for asymmetry generation, including the interactions and the masses of the right-handed neutrino, which is the key player here, can leave distinctive traces in the statistics of the spatial distribution of galaxies or the cosmic background of stars. microwave and can be measured accurately,” said Dr. Cui, though those measurements have yet to be made, she added. “Astrophysical observations anticipated in the coming years can potentially detect such signals and unravel the cosmic origin of matter.”

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