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Can 'early' dark energy solve the mystery of the expansion of the universe?  - Scientific news

Can ‘early’ dark energy solve the mystery of the expansion of the universe? – Scientific news

The matter described in two separate studies published in arXiv can be considered as a second type of dark energy.[1][2] This material, identified by the scientists who conducted the above studies, was described as “early dark energy,” based on data collected between 2013 and 2016 by the Atacama Cosmology Telescope (ACT) located in Chile, one of the articles explains. Nature site.
This discovery could be useful in understanding why and at what speed the expansion of the universe is accelerating.

The mystery of the universe’s expansion speed

In fact, the speed of the expansion of the universe has become a real mystery because the data collected over the years simply do not match. We are talking first of all about data about the early universe that does not seem to be consistent with the data we see today regarding the speed of the expansion of the universe.
According to data collected during the European Space Agency’s Planck mission, it is known that the universe is expanding at a certain speed. However, more accurate measurements have been made over the past few years and it has been found that it appears to be faster. Some studies show differences of 5-10%.

The second type of dark energy

The second type of dark energy theorized by researchers must have existed, permeating the entire universe, during the first 300,000 years after the Big Bang.
According to Colin Hill, one of the authors of one of the two studies, if this early dark energy was indeed pervasive in the early universe, it must have left a strong enough mark that it can still be detected today.

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The cosmic microwave background has been analyzed

The discovery was made through data collected by ACT on the so-called cosmic microwave background (CMB). It’s primordial radiation that spread throughout the universe when it all began, and it’s considered a residual glow from the Big Bang itself.
The researchers plotted small variations in the CMB differences by obtaining additional evidence supporting the Standard Model of cosmology.
According to the latter, the first evolution of the universe would have occurred with the formation of the three main components that, essentially, should represent the whole universe today: ordinary matter, dark matter, and dark energy.

The concept of “elementary dark energy” was previously theoretically developed

In the past, cosmologist Mark Kamionkowski has already proposed the concept of “primary dark energy” to explain differences in measurements related to the expansion speed of the universe.
According to Kamionkowski, during the early stages some kind of fluid permeated the universe, a fluid that will then disappear within a few hundred thousand years. This fluid, while not changing the expansion rate of the universe, could have caused the plasma to cool, affecting the data we collect today by observing the CMB.

The universe must be 12.4 billion years old, not 13.8

According to the two studies proposed on arXiv, the data collected thanks to ACT fits better with the model that includes this early dark energy than the standard model for the expansion of the universe. These two studies calculate that the universe is now 12.4 billion years old, not the 13.8 billion years calculated by the Standard Model.
As a result, the current rate of expansion is about 5% faster than the rate calculated by the standard model. These are scales closer to those collected by astronomers in recent years.

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More notes may clarify this issue

The same researchers admit that we’re still too early to prove the fact that this extra “dark” matter, conceptually distinct from the dark energy we see today, was actually present during the first hundreds of thousands of years of the universe.
However, they hope that with more observations, which can also be done with other telescopes including the Antarctic Antarctic Telescope, more rigorous tests can be carried out and important new information can be obtained.

Notes and insights

  1. [2109.04451] The Atacama Telescope for Cosmology: Constraints on Early Dark Energy Before Recombination (he is)
  2. [2109.06229] Dark Energy in Early Times and ACT: A Larger Hubble Constant Without Late Overtures (he is)

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