Dark matter makes up about 27% of the universe’s content, but its nature remains a mystery. Unlike regular matter, which emits electromagnetic radiation, dark matter does not. Instead, scientists have inferred its existence only through its gravitational effects on visible matter.
Researchers are exploring new theories to explain dark matter’s behavior. One such theory is self-interacting dark matter (SIDM), which suggests that dark matter particles can interact with each other if they fly close enough. This interaction would cause them to bounce off, creating large-scale structure in the universe.
Studies have shown that SIDM can help explain the existence of supermassive black holes early on in the universe. These black holes are difficult to form and are often scarce, but SIDM provides a possible explanation for their creation.
A study led by UC Santa Cruz researchers found that if a fraction of dark matter is ultra-strongly self-interacting, it could have caused gravothermal collapse at early times in dark matter halos, leading to the formation of supermassive black holes. This interaction also causes dark matter particles to bunch up, allowing them to collapse into black hole seeds.
O’Donnell’s talk focused on constraints on dark matter self-interaction in galaxy clusters. He found that current constraints are different at small and large scales, but could be consistent if there is a velocity dependence. Strong gravitational lensing is being used to study this effect, as it allows researchers to measure the mass enclosed in a particular region.
Researchers are excited about the potential of these new theories to explain phenomena in our universe. Other extensions of dark matter research include axion dark matter and warm dark matter, which offer unique explanations for unknown phenomena.
Source: https://theaggie.org/2025/03/13/the-mysteries-of-self-interacting-dark-matter-and-why-it-matters