A universe without dark energy? mathematicians challenge the standard model of cosmology

This composite image features one of the most complicated and dramatic collisions between galaxy clusters ever seen. Known officially as Abell 2744, this system has been dubbed Pandora”s Cluster because of the wide variety of different structures found. Data from NASA’s Chandra X-ray Observatory (red) show gas with temperatures of millions of degrees. In blue is a map showing the total mass concentration (mostly dark matter) based on data from NASA’s Hubble Space Telescope, the VLT (Very Large Telescope), and the Subaru telescope. Optical data from Hubble and VLT also show the constituent galaxies of the clusters. Astronomers think at least four galaxy clusters coming from a variety of directions are involved with this collision.

doi.org/10.1098/rspa.2025.0912
Credibility: 989
#Dark Energy

Mathematicians are questioning whether dark energy truly exists

A new study suggests that the accelerating expansion of the universe can be explained without it, shaking the foundations of the current cosmological model.

Researchers at the University of California, Davis, published an analysis in the journal “Proceedings of the Royal Society A”.

They show that Einstein’s equations combined with fluid dynamics (known as the Einstein-Euler equations) reveal instabilities in the standard model of the expanding universe.

These equations are used to describe galaxies, black holes, and the cosmos itself.

The dominant model today is Lambda-CDM, which includes cold dark matter and the famous dark energy to explain why the universe is expanding faster and faster.

But, according to the authors, this model is unstable, like a pencil balanced on its tip: it seems like a perfect solution to the equations, but any small perturbation knocks it down.

Unstable solutions, in physics, are not considered real because we have never observed them in nature.

Blake Temple, professor emeritus of mathematics and lead author of the study, explains that Friedmann spacetimes-the mathematical models that describe the uniform expansion of the universe-are particularly unstable, both at small and large scales, especially near the Big Bang.

This suggests a simpler and more natural explanation, which falls entirely within Einstein’s theory of gravity, without needing to add dark energy.

Dark energy was proposed about 30 years ago to justify the observed acceleration.

The idea dates back to Einstein himself, who in 1915 introduced a “cosmological constant” to try to keep the universe static.

After Hubble discovered the expansion, Einstein called it his biggest mistake.

Decades later, in the 1990s, the constant was revived and associated with dark energy.

The researchers investigated alternatives and used self-similar versions of Einstein’s equations (which maintain the same pattern at different scales).

They concluded that the acceleration arises naturally from the equations, without the need for a cosmological constant or dark energy.

Furthermore, the study challenges the Copernican principle, which states that the Earth (or our position) does not occupy a special place in the universe.

According to them, both the current model and a spherically symmetrical distribution would require us to be in a privileged position for everything to make sense.

In short, the Big Bang may resemble the Friedmann model near the center, but further away, we observe natural accelerations.

This paves the way for simpler explanations, based solely on Einstein’s general relativity, without invoking mysterious components such as dark energy.

The work was funded by institutions in the United Kingdom and the United States and brings a new perspective to understanding the cosmos.

Published in 06/12/2026 13h33

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