A new study suggests that the universe may have existed in a “bouncing” cycle of contraction and expansion phases before the Big Bang, challenging the idea that the Big Bang was the beginning. This theory could have profound implications for our understanding of the cosmos, particularly concerning black holes and dark matter.
The study proposes that dark matter could be composed of primordial black holes formed during the universe’s last contraction phase, just before the current expansion. If true, gravitational waves from these black holes might be detectable by future observatories, offering a potential confirmation of this dark matter formation scenario.
Current observations show that dark matter constitutes about 80% of the universe’s mass, yet its nature remains unknown. In the study, researchers explore a model in which primordial black holes formed from density fluctuations during the universe’s contraction phase. Published in the *Journal of Cosmology and Astroparticle Physics*, the study investigates a non-singular matter bouncing cosmology where the universe first contracted and then rebounded, leading to the Big Bang and the subsequent expansion.
This bouncing cosmology suggests that near the rebound, matter density was so high that small black holes could form from quantum fluctuations, making them potential dark matter candidates. These black holes, which could weigh as much as asteroids, might still exist today if they avoided complete decay through Hawking radiation.
The study’s findings align with current observations of space curvature and the cosmic microwave background. Future gravitational wave observatories, like LISA and the Einstein Telescope, could detect the waves produced by these primordial black holes, providing a way to test whether they contribute to dark matter. However, it may take over a decade before these observatories are operational.
The study highlights a unique mechanism for dark matter formation, distinct from the traditional inflation-based models, and emphasizes the ongoing exploration of primordial black holes as potential dark matter candidates.