The universe appears to have slowed its evolution: this contradicts theoried and puzzles scientists

Something is probably wrong with our Universe or with the models of the space developed by humankind. Over time, the matter in the Universe is becoming more and more dense, but this is happening more slowly than expected.

This is stated in a study published in Physical Review Letters. Scientists believe that such a slowdown in the evolution of such a large-scale structure as the Universe may indicate the existence of new particles or fields or that scientists are mistaken in their understanding of what dark matter is.

The evolution of the universe is driven by two forces: dark energy makes the cosmos expand, while gravity pulls matter towards it.

The most common model of cosmology called the Lambda-CDM suggests that this will eventually lead to a cosmic web of galaxies becoming denser and denser, with cosmic voids growing and becoming empty of matter, as only space, not the cosmic objects within it, grows.

A recent study conducted by Nhat Minh Nguyen from the University of Michigan and his colleagues showed that this is exactly what is happening, but there is one significant difference.

The researchers collected data from various sources on the structure of the early Universe and its current state. They found that the process of structure growth is slowing down at an unexpected rate. As predicted, the cosmic web is becoming denser and the voids are getting bigger and more empty, but all this is not happening at the rate predicted by the Lambda-CDM.

"Many different probes exploring the Universe at different times and on different scales point to the same thing: the growth of structure has been much slower recently than we expect from the standard model," Nguyen said.

He added that the scientists expected to find a certain slowdown in the rate of evolution of the Universe, but "this slowdown is more noticeable."

The deviation in the researchers' calculations with the standard model reaches 3.7 sigma. This means that there is a probability of about 1 in 4600 that such data is a statistical accident if the standard model described the cosmos right.

The slowdown in the expansion of the Universe can also explain the stresses that have been detected in previous space observations.

As NewScientist writes, Mike Hudson from the University of Waterloo in Canada notes that there are many suggestions in the scientific literature that "the Lambda-CDM is wrong in some ways," but this view is not generally accepted in the scientific community.

Scientists cannot say what the reason for this sharp slowdown might be, as it remains a mystery to them at the moment. But until it is resolved, scientists will not be able to modify the standard Lambda-CDM model to better fit the reality.

"Many of the models of modified gravity that we know of would lead to structural strengthening, not slowing down. The fact that we see a slowdown is a very interesting hint of what might be happening," said Jiamin Hou of the Max Planck Institute for Extraterrestrial Physics in Germany.

At the same time, Nguyen adds that the problem cannot be solved by simply adding more dark energy.

"The reason for this may be something that requires new fields, i.e. new particles or new interactions, i.e. new forces, perhaps between dark matter particles," Nguyen said.

According to him, if dark matter interacts or decays differently than scientists had predicted, this could explain the measurements. However, more observations are needed to find out for sure.

Earlier, OBOZREVATEL reported that scientists have discovered evidence of cosmic symmetry breaking for the first time.

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