The Summer 2023 research group. L to R: Jared Diks ’25, Lance Chen ’25, Shafaat Mahmud ’26, Jillian Paulin ’23, Richard Casey ’24, Assistant Professor of Physics and Astronomy Cosmin Ilie
Recent research by a student-faculty team at Â鶹´«Ă˝Ół» unlocks new clues that could radically change the world’s understanding of the origin of dark matter.
Assistant Professor of Physics and Astronomy Cosmin Ilie and Richard Casey ’24 have explored an idea put forth by two scientists at the University of Texas at Austin, Katherine Freese and Martin Winkler, suggesting that dark matter may have originated from a separate “Dark Big Bang,” occurring shortly after the birth of the universe.
It is widely accepted that all the matter filling our universe (including dark matter) originated from one major event — the Big Bang. This corresponds to the end of the cosmic inflation period, when the vacuum energy that drove the very brief extreme expansion initial phase of our universe was converted into a hot plasma of radiation and particles.
One of the most pressing mysteries is the origin and the nature of dark matter, which accounts for about 25% of the energy budget of the Universe today. While not yet directly detected in underground experiments, or observed in accelerators, the gravitational effects of dark matter have been firmly established on galactic and extragalactic scales. Moreover, dark matter leaves observable imprints on the electromagnetic afterglow of the Big Bang, the so-called cosmic microwave background radiation.
In 2023, Freese and Winkler proposed that dark matter, unlike ordinary matter, may have arisen from a distinct Big Bang event, which could have taken place months after the conventional Big Bang [1]. In this model, dark matter particles are produced via the decay of a quantum field that only couples to the Dark Sector and is initially trapped in a false metastable vacuum state.
In their recent study [2], Ilie and Casey explore and refine this Dark Big Bang model by determining all the possible scenarios for its realization that remain consistent with current experimental data. Most notably, their work uncovers a previously unexplored range of possible parameters that could explain dark matter’s origin. The study also determines the potential observable consequences of these new scenarios, particularly the generation of gravitational waves that could be detectable by future experiments.
“Detecting gravitational waves generated by the Dark Big Bang could provide crucial evidence for this new theory of dark matter,” said Ilie “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.”
The 2023 detection of background gravitational waves by the NANOGrav collaboration, part of IPTA, could be linked to a realization of the Dark Big Bang. As future experiments provide more precise measurements, the study’s findings could help refine our understanding of the parameters governing the Dark Big Bang and potentially confirm it as the true origin of dark matter.
The implications of these discoveries could extend beyond dark matter, as they offer a new perspective on the early history of the universe and the forces that shaped its evolution. The search for answers to the mysteries of dark matter and its origins continues to drive research at the forefront of modern cosmology.
[1] Katherine Freese and Martin Winkler, Phys.Rev.D 107 (2023) 8, 083522
[2] Richard Casey and Cosmin Ilie, Phys.Rev.D (2024) 110, 103522