Neutrinos and dark matter are two mysterious parts of the Universe. Scientists don’t fully understand them yet, but they are essential for how the Universe has changed over time. By comparing measurements of the Universe at different stages in its history, researchers might discover new clues about what neutrinos and dark matter are really like.
If neutrinos and dark matter interact with each other, they could leave special signs in the way we observe the Universe. These signs might give us a rare chance to learn about hidden physics beyond the standard model of the Universe.
Scientists at the University of Sheffield have found hints that dark matter and neutrinos interact. The surprising part is that this discovery challenges the standard model of cosmology (called ΛCDM), which assumes that dark matter and neutrinos don’t interact at all. If they do, it could open up a new way to understand the hidden physics of the Universe.
Early universe clues come from the ACT in Chile and ESA’s Planck Telescope, both peering into the faint glow left by the Big Bang. Later universe snapshots are captured by the Dark Energy Camera in Chile and galaxy maps from the Sloan Survey.
The team studied how matter is spread across the Universe (the matter power spectrum) using advanced computer simulations. These simulations track how tiny ripples in matter grow under the pull of gravity. Since interactions between neutrinos and dark matter are thought to stop very early in cosmic history, they don’t affect the scales being studied.
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To speed up the process, the team used an emulator, a tool that combines results from multiple pre-run simulations to smoothly fill in gaps, so they could efficiently scan different cosmological scenarios.
Co-author of the study, Dr Eleonora Di Valentino, a Senior Research Fellow at the University of Sheffield, said: “Our results address a long-standing puzzle in cosmology. Measurements of the early Universe predict that cosmic structures should have grown more strongly over time than what we observe today.”
“However, observations of the modern Universe indicate that matter is slightly less clumped than expected, pointing to a mild mismatch between early- and late-time measurements.”
“This tension does not mean the standard cosmological model is wrong, but it may suggest that it is incomplete.”
By adding cosmic shear data (tiny distortions in galaxy shapes caused by gravity) to their analysis, scientists found that a small interaction strength between dark matter and neutrinos (about 𝑢≈10−4) neatly explains puzzling signals seen by the Atacama Cosmology Telescope. Even more exciting, this interaction also helps solve the long-standing S8 tension, a mismatch in how clumpy the Universe looks in different measurements.
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When combined with data from the Dark Energy Survey (DES Y3), the results show a strong (nearly 3σ) hint that dark matter and neutrinos really do interact.
“Our study shows that interactions between dark matter and neutrinos could help explain this difference, offering new insight into how structure formed in the Universe.”
Journal Reference:
- Zu, L., Giarè, W., Zhang, C. et al. A solution to the S8 tension through neutrino–dark matter interactions. Nat Astron (2026). DOI: 10.1038/s41550-025-02733-1
