Overall, the universe started off pretty smoothly, but thinking goes on, but quantum shakes space with tiny particles of matter. As space expands, these dense points stretch out even as small ripples continue to arise. When inflation stops, the young universe is left with dense spots from small to large, which will then become galaxies and galaxy clusters.
All theories of inflation nail this two-point correlation function. To distinguish between competing theories, researchers need to measure Smaller correlations, higher scores—For example, the relationship between the angles formed by a trio of galaxies.
Usually, cosmologists propose an inflationary theory involving certain exotic particles, then push it forward to calculate the three-point correlation functions it will leave in the sky. , helping astronomers have a search goal. In this way, the researchers tackle the theories one by one. “There are many, many, many possibilities that you can look for. In fact, countless Daan Meerburg, a cosmologist at the University of Groningen.
Pajer turned that process around. Inflation is thought to have left ripples in the fabric of space in the form of gravitational waves. Pajer and his collaborators started with all three-point functions that could describe these gravitational waves and tested them with the matrix test, discarding any functions that failed to achieve unity.
In the case of a certain type of gravitational wave, the team found that the unique three-point functions are few and far between. In fact, only three people passed the test, researchers report in a preprint posted in September. The results are “very remarkable,” said Meerburg, who did not participate. If astronomers ever discovered primordial gravitational waves—and efforts are continuing—These will be the first signs of inflation to look for.
Positive signs
The cosmological optical theorem guarantees that the probabilities of all possible events add up to 1, just as a coin certainly has two sides. But there is another way of thinking about unity: The odds of each event must be positive. No coin can have a negative chance of landing on the tail.
Victor Gorbenko, a theoretical physicist at Stanford University, Lorenzo Di Pietro of the University of Trieste in Italy, and Shota Komatsu of CERN in Switzerland recently approached unity in de Sitter spaces from this point of view. They wonder what the sky would be like, in these monstrous universes that broke this positive rule?
Inspired by the Escher world, they were intrigued by the fact that anti-de Sitter spaces and de Sitter spaces share one fundamental characteristic: Viewed properly, each can look the same at any scale. . Zoom in near the boundary of Escher Circle limit III woodcarvings, and the shrimp-rich fish have identical proportions to the whores in the middle. Likewise, quantum ripples in the inflated universe create dense spots large and small. This common property, “proper symmetry”, recently allowed Taronna, who has worked with Charlotte Sleight, a theoretical physicist at Durham University in the UK, has come up with a popular mathematical technique to circumvent theories about the boundary between two worlds.
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Gorbenko’s group further developed this tool, allowing them to end inflation in any universe — the tangle of density ripples — and break it down into a total of similar patterns. They found that for unitary universes, each wave would have a positive coefficient. Any theory that predicts negative waves will not be good. They described their experiment in a preprint in August. At the same time, an independent group led by Joao Penedones of the Swiss Federal Institute of Technology Lausanne arrived same result.
The positive test is more precise than the cosmological optical theorem, but less readily available for real data. Both of the simplified positive groups, including removing gravity and assuming a perfect de Sitter structure, will need to be modified to accommodate our messy, gravitational universe. But Gorbenko calls these steps “concrete and doable.”
Cause for hope
Now that bootstrappers are perfecting the concept of what unity looks like for the outcome of a de Sitter expansion, they can turn to other classical bootstrapping rules, such as the expectation that the cause will come before the effect. It is currently unclear how to see traces of causation in a timeless snapshot, but this was once true for unity.
“That’s the most interesting thing that we still don’t fully understand,” Taronna said. “We don’t know what is not causal in de Sitter.”
