One of the biggest unsolved problems in physics has to do with combining quantum mechanics and general relativity – two theories that are equally successful. And the latest attempt to close the bridge brings into the equation the explosion that started everything: the Big Bang.
In a recent paper in Physical Review Letters, physicists at the University of Waterloo and the Perimeter Institute in Canada propose a new theory that the rapid expansion of the universe in its early stages is consistent with another model of quantum gravity. According to the math team’s predictions, the Big Bang arises naturally from that theory, called quadratic gravity, an updated version of Einstein’s classical theory of gravity.
“Think of Einstein raised to the second power,” Jerome Quintin, co-author of the study of cosmology, told Gizmodo. The new work “takes formal calculations from quantum field theory and creates a bridge between them and real-world conditions and observations, allowing us to test these formal ideas and calculations.”
The early days of the universe
The Big Bang refers to the big explosion that caused the universe to grow into the world we see today. In the “normal” picture, the universe starts out small, hot, dense, and generally isotropic, explained Ruolin Liu, lead author of the study and a postdoctoral student, to Gizmodo.
A popular explanation for this phenomenon is called the inflationary state, which means that a hypothetical inflaton particle “proliferated a rapid, rapid expansion” in the early days of the universe, Liu said. But this idea destroys before we go to the time of astrology, which corresponds to a higher power in the universe, he added.
Finding the quantum solution
The team wondered if there was a way to explain the Big Bang without dealing with many new species. And if quantum effects enter the equation, it can be even better. They decided on quadratic gravity, which remains statistically stable at high energies like the Big Bang, according to the paper.
Interestingly, the team’s calculations revealed that the quadratic terms of the model led to the expansion of the universe, after which the structure of space-time collapsed into the known effects of general relativity. In addition, Liu added that the mathematical predictions are in good agreement with what has been observed in the universe created by modern technology, which has been “combating other common forms of inflation.”
A tested hypothesis
More importantly, the team believes that its theory can be fully tested—which is often not the case in quantum gravity models. This model predicts the minimum number of magnetic waves produced during inflation, which next-generation detectors will be able to capture.
Niayesh Afshordi, the study’s senior author and a physicist, told Gizmodo that gravity is often dismissed as “theoretical,” but the new work “shows that gravity can be fully studied and integrated into the universe, with some predictions for the future.”
It’s waiting for a revolution, kind of
Indeed, if the group’s results can be verified – empirically and empirically – the implications will be transformative. But as with any prediction, there isn’t much we can say for sure until the new product undergoes independent testing and testing.
That said, it’s also true that we live in a very good time for cosmology. For example, LISA, a next-generation lander that can do what the team wants, is scheduled to launch in 2035. NASA’s Nancy Grace Roman telescope, after fighting a budget storm, will launch as planned. And the small Vera C. Rubin Observatory bombards astronomers with hundreds of thousands of observations.
So even if the latest proposal doesn’t end up being “it,” we may be entering a period that allows us to draw a hypothesis from the realm of testable ideas. And that’s fun!
Related article: A Radical New Theory Rewrites the Story of the Early Universe
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