The Big Bang may not have been the beginning of the universe, according to a cosmological theory that suggests the universe can “jump” between stages of compression and expansion. If true, the theory could have profound implications for the nature of the cosmos, including its two most mysterious components: black holes and dark matter.

With this in mind, a recent study suggests that dark matter may be formed from black holes that formed during the transition from the final contraction of the universe to the current expansion phase before the Big Bang. If this hypothesis is correct, gravitational waves created during the black hole formation process could be detected by future gravitational wave observatories, providing an opportunity to confirm this dark matter formation scenario.

Observations of the motions of stars in galaxies and the cosmic microwave background (the afterglow of the Big Bang) suggest that about 80% of all matter in the universe is dark matter, which does not reflect, absorb, or emit light. Despite its large amount, scientists still have not determined what dark matter is made of.

In a new study, researchers investigated a scenario in which dark matter consists of primordial black holes created by density fluctuations that occurred during the final stages of the universe’s compression, shortly before the period of expansion we see now. They published their findings in June in the Journal of Cosmology and Astroparticle Physics.

Space jump

The traditional cosmological view of the universe suggests that it began with a singularity, followed by a period of extremely rapid expansion called inflation. However, the authors of the new study analyzed a more exotic theory known as non-singular matter rebound cosmology, which proposes that the universe first went through a compression phase, which ended with a rebound due to the increasing density of matter, leading to the Big Bang and the accelerating expansion we see today.

In this bouncing cosmology, the universe was shrunk to a size about 50 times smaller than it is today. After the bounce, photons and other particles that signal the Big Bang were born. The density of matter near the bounce was so high that small black holes formed due to quantum fluctuations in the density of matter, making them good candidates for dark matter.