Cosmologists are approaching the logical laws of the Big Bang

The universe began generally smoothly, as expected, but the quantum movement of printed space with small droplets of extra matter. As the space expanded, these dense patches stretched, even as the small waves continued to appear. When inflation stopped, the young cosmos was left with dense patches ranging from small to large, which would turn into galaxies and galaxy clusters.

All theories of inflation nail this correlation function from two points. To distinguish competing theories, researchers must measure finer correlations from a higher point-relationships between the angles formed by three galaxies, for example.

Usually, cosmologists propose a theory of inflation involving certain exotic particles, and then push it forward to calculate the three-point correlation functions it will leave in the sky, giving astronomers a search target. In this way, researchers tackle theories one by one. “There are many, many, many possible things you could be looking for. In fact, an infinite number, “he said Daan Meerburg, cosmologist from the University of Groningen.

Pajer reversed this process. Inflation is thought to have left waves in the fabric of space in the form of gravitational waves. Payer and his collaborators started with all possible three-point functions describing these gravitational waves and tested them with the matrix test, eliminating all functions that failed to unite.

In the case of a certain type of gravitational wave, the group found that the unitary three-point functions are few and far between. In fact, only three pass the test, the researchers said in prepress published in September. The result is “very remarkable,” said Meerburg, who was not involved. If astronomers ever find primary gravitational waves …and efforts continue– These will be the first signs of inflation that you should look for.

Positive signs

The cosmological optical theorem ensures that the probabilities of all possible events are equal to 1, just as a coin certainly has two sides. But there is another way of thinking about unitarity: the chances of any event must be positive. No coin can have a negative chance of falling in queues.

Victor Gorbenko, theoretical physicist at Stanford University, Lorenzo di Pietro from the University of Trieste in Italy, and Shota Komatsu from CERN in Switzerland recently approached the unitarity of the de Sitter space from this point of view. What would heaven look like, they wondered, in bizarre universes that violate this law of positivity?

Inspired by Escher’s world, they were intrigued by the fact that the anti-de Sitter space and the de Sitter space share a fundamental characteristic: if viewed correctly, each can look the same on all scales. Zoom near the border of Escher’s Round III limit wood carving, and the shrimp are identical in proportions to those in the middle. Similarly, quantum waves in the inflatable universe generated large and small dense spots. This common feature, “conformal symmetry,” has recently allowed Taron, with whom he works Charlotte Slate, a theoretical physicist from the University of Durham in the United Kingdom to transfer a popular mathematical technique for breaking down theories about the boundaries between the two worlds.


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Gorbenko’s group further developed the tool that allowed them to take over the end of inflation in each universe – a mixture of density waves – and break it down into a set of wavy patterns. For unitary universes, they found, each wave will have a positive coefficient. Any theories predicting negative waves would not be good. They described their test in prepress in August. At the same time, an independent group led by Joao Penedones of the Swiss Federal Institute of Technology in Lausanne arrived the same result.

The positivity test is more accurate than the cosmological optical theorem, but less ready for real data. Both positive groups have made simplifications, including eliminating gravity and adopting a flawless de Sitter structure that will need to be modified to fit our cluttered, gravitational universe. But Gorbenko called the steps “concrete and feasible.”

Reason for Hope

Now that bootstrappers are getting closer to the idea of ​​what unitarity looks like as a result of de Sitter’s expansion, they can move on to other classic startup rules, such as the expectation that the causes must come before the consequences. It is not clear at this time how to see traces of causation in a perpetual photograph, but the same is sometimes true of unitarity.

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

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