“The fact that our present-day universe is dominated by matter remains one of the most complex, long-standing mysteries in modern physics,” University of California, Riverside professor of physics and astronomy Yanou Cui said in a statement released this week. “A subtle imbalance or asymmetry between matter and antimatter in the early universe is required to achieve the present dominance of matter, but it cannot be realized within the known framework of fundamental physics.” There are theories that may answer this question, but they are extremely difficult to test using laboratory experiments. Now, in a new paper published Thursday in the journal Physical Review Letters, Dr. Cui and her co-author, Zhong-Zhi Xianyu, an assistant professor of physics at Tsinghua University in China, explain that they may have found a job around using the hysterical glow of the big bang itself to run the experiment. The theory that Drs Cui and Zhong-Zh wanted to explore is known as leptogenesis, a process involving particle decay that could have led to the asymmetry between matter and antimatter in the early universe. An asymmetry in certain types of elementary particles in the very early moments of the Universe, in other words, could have grown over time and through further particle interactions into 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 that create the matter-antimatter asymmetry,” Dr. Cui said in a statement. “It includes a new fundamental particle, the right-handed neutrino.” But, Dr. Cui added, producing a right-handed neutrino would require much more energy than can be produced in particle accelerators on Earth. “Testing leptogenesis is nearly impossible because the mass of the right-handed neutrino is typically many orders of magnitude beyond the reach of the highest energy accelerator ever built, the Large Hadron Collider,” he said. The idea of Dr Cui and her co-authors was that scientists might not need to build a more powerful particle accelerator 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 mere fractions of a second after the big bang, …. “Cosmic inflation provided a highly energetic environment, allowing the production of new heavy particles as well as their interactions,” said Dr. Cui. “The inflationary universe behaved exactly like a cosmological accelerator, except that the energy was up to 10 billion times greater than any man-made accelerator.” Furthermore, the results of these physical accelerator cosmological experiments can be preserved today in the distribution of galaxies, as well as in 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 universe . “Specifically, we show that the key conditions for creating asymmetry, including interactions and masses of the right-handed neutrino, which is the key player here, can leave distinctive fingerprints on the statistics of the spatial distribution of galaxies or the cosmic microwave background and can be accurately measured,” Dr. Cui said, although making those measurements, he added, remains to be done. “Astrophysical observations expected in the coming years may potentially detect such signals and reveal the cosmic origin of matter.”
