New research suggests that if dark matter was made up of “dark photons,” it would not have heated the early cosmos as scientists previously thought. If correct, this discovery could represent a paradigm shift in the search for the most mysterious things in the universe. Dark matter remains so elusive because, despite outweighing the everyday matter that makes up stars, planets, moons, and our bodies by five to one, it is effectively invisible. This is because it does not interact with light. And the fact that electrons, protons, and neutrons interact with light (or, more accurately, electromagnetic radiation) has inspired the search for particles beyond the standard model of particle physics, leading to many hypothetical candidates for dark matter. One such candidate is the dark photon, the dark universe version of a photon carrying a force other than electromagnetism, which is the responsibility of standard photons. photons while they were still embedded in the thick, dense soup that filled the early cosmos. This would have further heated this already scorching hot plasma and left detectable trails of dark photons. This severely limits the search parameters in which dark photons could exist, to the point that many cosmological observations rule out the existence of dark photons. Now, new computer simulations show that the discarding of the dark photons may have been a bit hasty. The conversion of dark photons to photons would have been disrupted before significant heating could occur. This brings previously excluded search parameters back into play. “These exclusions said that the strength of dark matter had to be 10^8 times weaker than it actually can be,” team member Anson Hook of the University of Maryland said in a statement. “This paper opens up many new possibilities for searching for dark matter.” An illustration of a dark photon, a candidate for dark matter. (Image credit: Robert Lea (created with Canva)) The team behind this research first saw hints that the transformation of dark photons into photons may not be as simple as scientists had assumed when they realized that the amount of energy involved is suspiciously large. The problem, they began to suspect, was the fact that this process had been considered linear; In other words, the released energy is gradually and steadily converted into plasma. “The treatment for the last 15 years is a linear treatment. If you use that approximation, you can calculate the amount of energy transfer, and it is very large,” team member Junwu Huang of the Perimeter Institute said in the statement. “And I realized that it is not possible.” By performing their first computer simulations, Huang and his colleagues realized that the linear process fails to show the complete picture. “What we realized is that as energy is converted into the Standard Model plasma, the plasma actually goes crazy,” Huang said. “There are many nonlinearities in the system, and these nonlinearities basically disrupt the energy conversion after a small amount of energy is converted.” Dark matter seen at the center of a galaxy. (Image credit: Mattia Di Mauro (ESO/Fermi-Lat)) The research represents a significant expansion of the parameters in which dark photons could exist, considerably expanding this metaphorical hunting ground. In fact, it could also affect the search for hypothetical particles beyond the standard model of particle physics. “By correctly calculating the plasma of the early universe, experiments will explore new parameter spaces and potentially see something,” team member Mohamad Shalaby of the Perimeter Institute said in the statement. The team’s research was published August 13 in the journal Physical Review Letters.
