Original title: Cosmological extra dimensions can mimic dark energy
Mattia Villani · September 2026
Astronomers observe our universe expanding at an accelerating rate, usually credited to an unknown force called dark energy. The researchers tested if hidden extra dimensions could cause this effect instead. They modeled a universe with our four regular dimensions alongside tiny, curled-up extra dimensions shaped like a hypersphere. In this setup, the curvature and expansion rate of these extra dimensions interact directly with our normal space. This interaction mimics dark energy, altering the apparent matter density and acceleration. As a result, a universe holding only matter and extra dimensions matches observational data. Testing this with supernova data revealed evidence for 3-4 extra dimensions that are currently shrinking. These extra dimensions do not change the cosmic microwave background, but they do not solve the Hubble tension.
You are trying to understand why a balloon expands faster as it gets bigger. Normally you would think there is a hidden force pushing it. But it might be that the balloon's surface is connected to extra hidden chambers that are shrinking, and that shrinking pulls the surface outward. In this paper, the balloon's surface is our universe, and the hidden chambers are extra dimensions that are contracting, mimicking the effect of a dark energy force.
If confirmed, this would reshape our understanding of the universe's expansion. It suggests that dark energy, one of the biggest puzzles in physics, might not be a mysterious force but a geometric effect of extra dimensions. This could lead to new ways to test the nature of our cosmos using existing supernova data.
The model does not resolve the Hubble tension, a key discrepancy in cosmology. It also does not affect the CMB spectrum, so it may not address all observations. The evidence for extra dimensions comes from fitting to supernova data, and the model is simple; more complex effects might alter the conclusions.
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Cosmological extra dimensions can mimic dark energy — Mattia Villani
Abstract licence: CC0
Explanation generated by Synthesis from the abstract — it is not the original paper. This is a preprint, so it hasn't necessarily been peer reviewed.