Is mysterious dark energy constant in space and time?

In 2011, the Nobel Prize in Physics was awarded to those who discovered the latest acceleration of the expansion of the observable universe over the past few billion years. We expected a continuous decline after the Big Bang.

Contrary to what one might think at first glance without reading the explanations of the Nobel Committee, it is not about the discovery of dark energy. It’s a way to explain the acceleration of expansion and give some sense of what Einstein’s relativistic equations for gravity account for, his famous cosmological constant.

Among the possible explanations for this constant, Newton’s constant is a simple property of the theory of gravity as incorporated into this theory. It can also be the minimum energy density of a scalar field similar to Brout-Englert-Higgs.

In the latter case, Einstein’s cosmological constant is indeed a dynamic quantity in space but capable of evolving over time, which could help solve the current crisis in cosmology.

Quantum vacuum energy?

On the contrary, which can be a manifestation of the so-called zero-point potential of quantum fields, be it the electromagnetic field or the track fields for matter particles called quarks and leptons. There is also a contribution from the zero point of gravity. Incidentally, all of these zero points are the result of Heisenberg’s inequalities, which prevent a particle from simultaneously having an infinitely precise position and zero velocity. Hence the fundamental state of quantum field fluctuation and activity is essential and cannot be reduced. The cosmological constant must be constant in time and space, and it is impossible to extract energy from the quantum vacuum occupied by these fields, otherwise it involves another quantum dynamic.

Helge Kraag, a renowned historian of science from the University of Copenhagen, explains this article during a discussion about its publication.The Oxford Handbook of the History of Quantum Descriptions The problem of the zero-point potential of quantum fields is about its origin or quasi-cosmology. Click on the white rectangle in the lower right for a more accurate French translation. Then the English subtitles should appear. Then click on the nut to the right of the rectangle, then “Subtitles” and finally “Auto Translate”. Select “French”. © Ideas in Science

One way to decide between these theories is to make increasingly fine measurements in space and time of the value of the cosmological constant.

One way to do this is that the acceleration of expansion caused by dark energy acts like a kind of anti-gravity effect, with the expansion of space opposing classical gravity. The effect is negligible at the solar system and per-galactic level, but it will begin to be felt by the formation of galaxy clusters and by counteracting their motions.

Galaxy clusters bathed in extremely hot plasma and emitting X-rays as a result can be studied using the Erosita instrument, built by the Max-Planck Institute for Extraterrestrial Physics in Germany and part of the Russian-German Space Agency. Observational spectro-org.

Growth in the number of galaxies is inhibited by the nature of dark energy

Recently, I-Non Chiu of National Cheng Kung University in Taiwan, along with astrophysicists Ludwig-Maximilians-Universität München (LMU) Matthias Klein, Sebastian Bocquet and Joe Mohr published the first study of dark energy using eRosita, based on a study of galaxies. This resulted in an article that can be consulted in free access arXiv.

In the LMU press release accompanying this article, Matthias Klein explains “ We can learn a lot about the nature of dark energy by counting the number of galaxies forming in the Universe as a function of time – or from a direct observational perspective as a function of redshift. “. This number is a function of the properties of dark energy and the theories that predict them.

It was therefore determined within the framework of the named monitoring campaign eRosita is the ultimate equatorial-depth survey (eFEDS), a prelude that covers approximately 1% of the heavenly treasury.

About 500 galaxies are identical, distributed in a kind of temporal caret through the layers of light that comprise the observable universe studied over the past 10 billion years.

With the accuracy of the current measurements, the researchers again concluded that the energy density of dark energy appears to be uniform in space and constant in time.

Our results are in good agreement with other independent approaches, such as galaxy clusters and previous studies using weak gravitational lensing and the cosmic microwave background. So far, all observational evidence, including the latest eFEDS results, suggests that dark energy can be described by a simple constant. Sebastian Boquet concludes.

We should learn more through Euclid’s work and the telescope Vera Rubin. A variable cosmological constant means the reversal of one day’s expansion and one new big bang. Otherwise, the expansion would continue to eternity, but according to Nobel laureate in physics Roger Penrose, eternity would also end.

We know very little about the universe. The stuff that makes up 4% of its energy density – “ordinary” stuff like protons and neutrons – is only a very small part of the “recipe for the universe”. The remaining 96% composition is a mystery. Today, 26% is considered dark matter. However, the largest share, estimated at 70%, is made up of dark energy. To understand its nature, scientists observe incredibly large and extremely hot stars, clusters of galaxies, which are made up of thousands of galaxies moving at different speeds in a common gravitational field. Inside, these strange structures are filled with a thin and extremely hot gas that can be observed through its X-ray emissions. This is where eRosita’s X-ray “eyes” come into play. They make it possible to observe clusters of galaxies. To see how they move in the universe, and above all how fast they move. Hopefully these motions will tell us more about dark energy. © Deutsche Zentrum für Luft- und Raumfahrt (DLR)

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