Dark matter interactions?

Two of the most mysterious components in the Universe may not be as independent as we thought. A new study suggests that dark matter and neutrinos may be interacting. If so, it casts doubt on the standard model of cosmology and could finally be shining some light on the dark components of the cosmos.

For decades, astronomers have relied on the standard model of cosmology, known as the Lambda Cold Dark Matter (ΛCDM) model, to explain the origin and evolution of the Universe and its galaxies. It postulates that dark matter (an invisible component that makes up more than 80 percent of the matter in the Universe) and neutrinos (an elusive, nearly weightless elementary particle) exist independently without interacting.

New research published in Nature Astronomy challenges this view by presenting evidence that dark matter and neutrinos are not solitary travellers but instead engage in the subtle exchange of momentum.

This could solve a thorn in the side of the ΛCDM model known as the S8 tension – where the modern Universe appears significantly less “clumpy” than the dense structures predicted by data from the early Universe. This mismatch suggests that our understanding of the cosmic evolution may be incomplete. The study proposes that these neutrino-dark matter interactions induce ‘dark acoustic oscillations’, which dampen the growth of matter density and effectively smooth out the distribution of galaxies over billions of years.

By combining data from ESA’s Planck space observatory and the Atacama Cosmology Telescope with data from the Dark Energy Survey, the international team found a nearly 3 sigma preference (which is considered a “hint” in particle physics; a 5 sigma result is standard for a true discovery) for these interactions. Remarkably, the interaction strength appears to resolve the S8 discrepancy entirely, bringing early- and late-Universe observations into a coherent alignment.

Dark matter interactions?

Read More