"Decline in Cosmic Clumpiness Puzzles Astronomers"
Recent observations have shown that dark matter is less clumpy in the current Universe than it was shortly after the Big Bang, challenging the standard cosmological model. This discrepancy, known as the sigma-eight (S8) tension, has been confirmed by multiple experiments, including a six-year weak gravitational lensing survey by the Hyper Suprime-Cam on the Subaru Telescope. The findings, which are not likely due to error, suggest there may be a fundamental aspect of the Universe that we do not yet understand, potentially related to our models of dark matter or cosmological expansion. This issue is detailed in five separate papers in Physical Review D, and future, more powerful surveys may provide further insights.