Cosmic bounce model suggests black holes older than the Big Bang could explain dark matter

Researchers at the University of Portsmouth have explored a cosmological model in which the Universe did not begin with a singular Big Bang but emerged from a prior contracting phase that reversed into expansion, a scenario known as a cosmic bounce.

In this framework, quantum effects at extremely high densities could generate enough pressure to halt the collapse and drive a new expansion, avoiding the infinite singularity where known physics breaks down.

The study calculates that compact objects larger than roughly 90 meters could survive the transition from contraction to expansion, meaning black holes formed in the earlier phase would persist as "cosmic fossils" in the present Universe.

These relic black holes could constitute a substantial fraction, or potentially all, of the dark matter whose gravitational influence shapes galaxies and large-scale cosmic structure.

The model also offers a possible explanation for unexpectedly massive objects observed by the James Webb Space Telescope in the early Universe, since pre-existing black holes would not need to form from scratch after the bounce.

Lead author Professor Enrique Gaztañaga notes that the bounce scenario could simultaneously address the origin of inflation, the nature of dark energy, and the puzzle of dark matter within a single theoretical framework.

The researchers identify several observational tests, including searches for relic gravitational waves from the pre-bounce era and subtle patterns in the cosmic microwave background that might preserve information from before the Big Bang.

The work is published in Physical Review D, and the authors emphasize that much further work is needed to test these ideas against observational data.