Early dark energy would solve all cosmological problems

In 1915, a certain Albert Einstein managed to explain how gravity shapes the Universe. His theory, called general relativityturns out to be quite effective, both for modeling the movement of the planets much more finely than Isaac Newton achieved, but also for explaining the major structures of the Universe: galaxies, clusters of galaxies, etc. .

Over the next 10 years, astronomers confirmed that there are thousands, even billions, of galaxies and that they are all moving away from ours (except for the closest ones). The Universe is therefore dynamic: it has a beginning and a mysterious force causes its expansion.

General relativity actually has the capacity to predict and explain almost all phenomena observed in the cosmos, from black holes to gigantic galactic structures. However, in the more than 100 years since it was presented to the world, some mysteries have emerged, which today would be resolved thanks to the new model discussed here:

• A very brief and very intense period that cosmologists call Inflation (a sort of hyper expansion of space itself that occurred very soon after the Big Bang)
• Different measurements of the rate of expansion, discordant with each other by about 10% (this delicate problem is called “Hubble tension”)
• Identified very recently thanks to the James-Webb space telescope, the early presence in the Universe of galaxies that are already very bright and very large

But what is dark energy?

In 1998, when two teams of astronomers noticed that the expansion of the Universe, far from slowing down, was in fact accelerating, it was a revolution in cosmology. It was indeed necessary to “invent” a new force capable of explaining this acceleration. She was named dark energy and it would act opposite to gravity, as a repulsive force. The Nobel Prize in Physics was even awarded to Adam Riess for the discovery ofaccelerated expansion.

Usually, this dark energy is considered to act very weakly at the beginning of the history of the Universe, and increasingly stronger as the latter grows and “ages”.

Early Dark Energy (EDE) erases three of the biggest cosmological problems!

However, in recent months, certain cosmological theorists have proposed a different model of dark energy, called Early Dark Energy. This would have been around 10% more significant just after the Big Bang, and these small 10% have a very astonishing capacity:

• They explain the period of Inflation
• They solve the problem of different measurements of the expansion rate (the famous Hubble tension)
• They manage to explain the overly massive and early galaxies observed by James-Webb in the early days of the Universe

Many theorists, including in France at the CNRS, are looking at this EDE model, such as Vivian Poulin Detolle or the extremely famous Adam Riess. It is therefore promising. Other theorists, however, remain doubtful.

We asked a theoretical physicist specializing in GR what he thought about EDE, Olivier Minazzoli (astrophysicist at the Côte d’Azur Observatory): “I don't have a specific opinion on the EDE, which is a phenomenological model created to explain the Hubble tension. But we are not even sure of the reality of this tension. Also, I don't think adjusting equations to solve an observational problem is a good method. I prefer to first create a theoretical framework and then see how it improves the understanding of certain phenomena. That said, each method has its merits, everyone explores the avenues in their own way with more or less success. We’ll see.”