The laws of physics used to be different, which might explain why you exist


June 06, 2023

(Nanowerk News) The laws of physics must have been different in the early universe than they are today, according to a study conducted by University of Florida astronomers, which provides clues to why stars, planets, and life itself managed to form in the universe. universe.

After analyzing the distribution of millions, trillions of galaxy groups, scientists found that the laws of physics once preferred a set of shapes to their mirror image. It’s as if the universe itself used to favor left-handed things over left-handed things, or vice versa.

This finding, made possible in part by UF’s HiPerGator supercomputer, helps explain perhaps the biggest question in cosmology: Why does something exist? That’s because some kind of left-handedness in the earliest moments of creation is needed to explain why the universe is made of matter, the stuff that makes everything we see. The results also help confirm key tenets of the Big Bang theory of the origin of the universe.

“I’ve always been interested in the big questions about the universe. What was the beginning of the universe? What are the rules under which it develops? Why is there something rather than nothing?” said Zachary Slepian, a UF astronomy professor who supervised the new study. “This work answers those big questions.”

Slepian worked with UF postdoctoral researcher and first author of the study, Jiamin Hou, and Lawrence Berkeley National Laboratory physicist Robert Cahn to conduct the analysis. The three published their findings in a journal Monthly Notices of the Royal Astronomical Society (“Odd-parity mode measurements in a large-scale 4-point correlation function from the Sloan Digital Sky Survey Baryon Oscillation Spectroscopic Survey data release for the twelve galaxies CMASS and LOWZ”).

Mirror image

Their study was designed to look for violations of a concept known as “parity symmetry” in physics, which refers to mirror image reflections that are similar to left-handed or left-handed. Many things in physics can be said to be left-handed, such as the spin of the electron. The current laws of physics usually don’t care whether the spin is left or right. The application of the same laws of physics, or being symmetrical, regardless of left-handedness is referred to as parity symmetry.

The only problem is that the parity symmetry must have been broken at some point. Some violation of ancient parity — a kind of preference for left-handed or left-handed objects in the past — is needed to explain how the universe created more matter than antimatter. If the symmetry of parity had been maintained during the Big Bang, equal parts of matter and antimatter would have combined, annihilated each other, and left the universe completely empty.

So in a recent paper published in Physical Review Letters, Slepian, Hou and Cahn propose an inventive way of looking for evidence that parity was indeed violated during the Big Bang. Their idea was to imagine every possible combination of the four galaxies in the night sky. Connect the four galaxies together with an imaginary line, and you have a slanted pyramid, a tetrahedron. It’s the simplest 3D shape possible –and thus the simplest shape to have a mirror image, the ultimate test for parity symmetry.

Their method required analyzing one trillion possible tetrahedrons for each of the one million galaxies, an incredible number of combinations. “Finally we realized that we needed new mathematics,” said Slepian.

So the Slepian team developed a sophisticated mathematical formula that would allow large calculations to be carried out in a reasonable amount of time. It still requires a lot of computing power. “The unique UF technology that we have here with its HiPerGator supercomputer and advanced GPU allows us to run the analysis thousands of times at different settings to test our results,” he said.

The Slepian group found that, indeed, the universe imparted an initial preference for left-handed or right-handed bodies to the matter that eventually became today’s galaxies. (The complicated math makes it hard to tell whether that preference is for left-handed or right-handed.)

They established their findings with a level of certainty known as seven sigma, a measure of how unlikely it is to reach an outcome based solely on chance. In physics, results with significance of five sigma or higher are usually considered reliable because chance results at this level are less likely. A similar analysis, conducted by former members of Slepian’s lab using the method proposed by Slepian, Cahn, and Hou, identified the same universal hand preference, albeit with slightly lower statistical confidence due to differences in study designs.

It remains possible that uncertainty in the underlying measurements could explain the asymmetry. Fortunately, a much larger sample of galaxies from the next generation of telescopes can provide enough data to remove these uncertainties in just a few years. The Slepian group at UF will perform their analysis on this new, more powerful data as part of the Dark Energy Spectroscopy Instruments telescope team.

This is not the first time a parity violation has been seen, but it is the first evidence that a parity violation could affect the three-dimensional grouping of galaxies in the universe. One of the fundamental forces, the weak force, is also breaking parity. But its range is extremely limited, and cannot affect the scale of galaxies or explain the abundance of matter in the universe. That universal effect requires a parity breach to occur precisely at the time of the Big Bang, the period known as inflation.

“Because parity violations can only be printed in the universe during inflation, if what we find is true, it provides evidence of inflation,” said Slepian.

The Slepian lab’s findings cannot yet explain how the laws of physics change, which would require a new theory that goes beyond the Standard Model, a theory that explains our universe today. It is now a race for scientists to come up with this theory that can explain the ancient nature of the universe and the abundance of matter we see today.


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