Cosmologists study the logical laws of the Big Bang


The universe was generally quite stable at the beginning. This is the idea, but quantum swings leave a mark on space with tiny extra matter. As the space expands, these dense spots of light continue to extend, but small ripples continue to rise. When the inflation ceases, the young universe will leave dense dots from small to large, and these dots will continue to become galaxies and galaxy clusters.

All inflation theories have determined this two-point correlation function.In order to distinguish between competing theories, researchers need to measure More subtle and higher relevance——For example, the relationship between the angles formed by three galaxies.

Usually, cosmologists will propose a theory of inflation involving certain strange particles, and then derive it to calculate the three-point correlation function it will leave in the sky, thus providing astronomers with a search target. In this way, researchers deal with theories one by one. “You can look for many, many, many possible things. In fact, infinitely many,” said Ammelberg, A cosmologist at the University of Groningen.

Pajer reversed this process. Inflation is believed to have left ripples in the structure of space in the form of gravitational waves. Pajer and his collaborators started by describing all possible three-point functions of these gravitational waves, and used matrix tests to check them and eliminate any functions that did not conform to unity.

In the case of a certain type of gravitational wave, the team found that unitary three-point functions are rare.In fact, only three passed the test, the researchers announced In preprint Released in September. The result was “very remarkable,” said Melberg, who was not involved. If astronomers detect primitive gravitational waves–And working hard-These will be the first signs of inflation to look for.

Positive signs

The theorem of cosmic optics guarantees that the probabilities of all possible events add up to 1, just as a coin must have two sides. But there is another way of thinking about unity: the probability of each event must be positive. There is no negative chance for any coin.

Victor Gorbenko, A theoretical physicist at Stanford University, Lorenzo Di Pietro From the University of Trieste, Italy, and Komatsu Shota Researchers from the Swiss European Nuclear Research Center recently explored the unity of de Sitter space from this perspective. They want to know what the sky will look like in a strange universe that breaks this positive law?

Drawing inspiration from Escher’s world, they are interested in the fact that anti-de Sitter space and de Sitter space share a basic feature: if viewed in the right way, each space looks the same on all scales.Zoom in near the border of Escher Circle Limit III In the woodcut print, the shrimp skin fish has the same proportions as the big fish in the middle. Similarly, quantum ripples in the expanding universe will produce dense dots large and small. This common characteristic, “conformal symmetry,” has recently made Taronna Charlotte Slater, A theoretical physicist at Durham University in the United Kingdom, transplanted a popular mathematical technique to break the boundary theory between two worlds.


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Gorbenko’s team further developed the tool, allowing them to end inflation—a hodgepodge of density ripples—in any universe and break it down into a sum of wave-like patterns. They found that for a single universe, every wave has a positive coefficient. Any theory that predicts negative waves is useless.They describe their test In preprint In August.At the same time, an independent team consists of Joao Penedones Students from the Swiss Federal Institute of Technology Lausanne arrive Same result.

The positivity test is more accurate than the optical theorem of cosmology, but it is less prepared for real data. Both active groups have made simplifications, including removing gravity and assuming that the de Sitter structure is flawless, which will need to be modified to fit our chaotic, gravitational universe. But Gorbianco called these steps “concretely feasible.”

Cause of hope

Since the facilitators are approaching the concept of unity of de Sitter unfolding results, they can turn to other classic guiding rules, such as the expectation that the cause should precede the result. It is not clear how to see the traces of causality in the eternal snapshot, but unity used to be the same.

“This is the most exciting thing we still don’t fully understand,” Taronna said. “We don’t know what is not causation in de Sitter.”


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