A recent study by a student-faculty team at Colgate University has provided new insights that could significantly reshape our understanding of dark matter's origins.
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Assistant Professor of Physics and Astronomy Cosmin Ilie and undergraduate researcher Richard Casey ’24 built on an idea proposed by Katherine Freese and Martin Winkler from the University of Texas at Austin. Their theory suggests that dark matter might have originated from a separate "Dark Big Bang," occurring shortly after the universe began.
For decades, scientists have believed that all matter in the universe, including dark matter, came from one event: the Big Bang. This marked the end of a period called cosmic inflation, where the universe expanded rapidly, transforming vacuum energy into a hot plasma of particles and radiation.
Despite accounting for about 25 % of the universe’s energy, dark matter remains a mystery. It has not been directly detected in experiments or observed in particle accelerators. However, its presence is clear from the gravitational effects it has on galaxies and other large-scale structures. Dark matter also leaves clues in the cosmic microwave background radiation—the faint glow left over from the Big Bang.
In 2023, Freese and Winkler suggested that dark matter might not have been created during the Big Bang itself. Instead, it could have come from a "Dark Big Bang" that occurred months later. Their model explains dark matter as particles produced by a quantum field that only interacts with a hidden "Dark Sector" and starts in an unusual vacuum state.
Building on this, Ilie and Casey explored how this Dark Big Bang model could work while staying consistent with current scientific data. Their research uncovered a range of new possibilities for how dark matter might have formed and outlined ways we could observe its effects—especially through gravitational waves. These ripples in spacetime, generated during the Dark Big Bang, could be detected by upcoming experiments.
Detecting gravitational waves generated by the Dark Big Bang could provide crucial evidence for this new theory of dark matter. With current experiments like the International Pulsar Timing Array (IPTA) and the Square Kilometer Array (SKA) on the horizon, we may soon have the tools to test this model in unprecedented ways.
Cosmin Ilie, Assistant Professor, Department of Physics and Astronomy, Colgate University
Interestingly, the gravitational waves detected in 2023 by the NANOGrav collaboration (part of IPTA) could already hint at the Dark Big Bang. As future experiments refine their data, we might get closer to confirming this theory and better understanding the forces that shaped our universe.
This research goes beyond dark matter. It opens a new window into the early history of the universe, giving scientists fresh ways to explore how everything we see today came to be. For now, the search continues to unravel one of the biggest mysteries in cosmology.
Journal Reference:
Casey, R. and I. Cosmin (2024) New Theory of Dark Matter Formation. Physical Review D. doi.org/10.1103/PhysRevD.110.103522