Dark Matter Decays and Slows the Universe's Growth ⚡ экспресс
Observations of fσ8 and weak lensing indicate that structure growth at z<1 is slower than in ΛCDM. This led to a model where dark matter interacts with its own decay radiation, and the friction force grows over time (unlike typical interactions that fade with expansion). The iDCDM model introduces just two new parameters and doesn't violate primordial nucleosynthesis or the CMB, but predicts a step-like weakening of growth, testable with DESI, Euclid, and Rubin. Comparison with current data favors it over standard cosmology.
The Universe grows like a metropolis: galaxies skyscrapers are erected on an invisible scaffold of dark matter—its gravity pulling in construction material. Meanwhile, dark energy makes the city itself continuously expand. Previously, it was assumed the scaffold compacts at a steady rate, despite the expansion of space. But recent measurements show that in recent epochs, the pace of construction has slowed down.
Astronomers suspect the issue lies with the scaffold itself: it gradually decays, emitting a 'dust' of lightweight particles. This dust, like a headwind, presses on the remaining dark matter and hinders further building. The most surprising thing is that the slowdown didn't start right away, but only a few billion years ago, as if the construction material suddenly started losing strength. The model predicts a clear signal—a characteristic break in the growth chart of galaxies on certain scales. Projects Euclid and Rubin will soon be able to test this hypothesis.
🎯 Dark radiation interacts so weakly with ordinary matter that it passes through Earth almost unnoticed.