In a paper to be published in the journal Physics Letters B, a duo of theoretical physicists from the University of Sussex shows that quantum gravity leads to lower and upper bounds on the masses of dark matter candidate particles, where the lower bound comes from limits on fifth force type interactions and the upper bound from the lifetime of a dark matter candidate.
This image was produced by a simulation showing the evolution of dark matter in the Universe. Image credit: Milennium-II Simulation.
There is overwhelming evidence that most of the matter in our Universe is dark and cannot be described by the Standard Model of particle physics.
The case for the existence of dark matter is strong because it comes from astrophysical and cosmological observations made on different scales and times in the Universe.
For example, the Cosmic Microwave Background or galaxy rotation curves involve very different physics and eras in the evolution of the Universe but they both require that about 75% of the matter content of the Universe consists of cold, non-baryonic, dark matter.
University of Sussex’s Professor Xavier Calmet and Ph.D. student Folkert Kuipers used the assumption that the only force acting on dark matter is gravity.
They calculated that dark matter particles must have a mass between 10-3 eV and 107 eV.
That’s a much tighter range than the 10-24 eV – 1019 GeV spectrum which is generally theorized.
What makes the discovery even more significant is that if it turns out that the mass of dark matter is outside of the range predicted by the team, then it will also prove that an additional force — as well as gravity — acts on dark matter.
“This is the first time that anyone has thought to use what we know about quantum gravity as a way to calculate the mass range for dark matter,” Professor Calmet said.
“We were surprised when we realized no-one had done it before — as were the fellow scientists reviewing our paper.”
“What we’ve done shows that dark matter cannot be either ‘ultra-light’ or ‘super-heavy’ as some theorize — unless there is an as-yet unknown additional force acting on it.”
“This piece of research helps physicists in two ways: it focuses the search area for dark matter, and it will potentially also help reveal whether or not there is a mysterious unknown additional force in the Universe.”
“It’s great to be able to work on research as exciting and impactful as this,” Kuipers added.
“Our findings are very good news for experimentalists as it will help them to get closer to discovering the true nature of dark matter.”
_____
Xavier Calmet & Folkert Kuipers. 2021. Theoretical bounds on dark matter masses. Physics Letters B 814: 136068; doi: 10.1016/j.physletb.2021.136068
