UC Riverside’s dark matter research program aims to make assumptions about particle physics.
As the name suggests, dark matter – matter that makes up about 85% of the mass of the universe – does not emit light, which is difficult to detect easily. His nature also remains in the dark.
Now a theoretical particle physicist from the University of California, Riverside, and his colleagues have a research project in Journal of High Energy Physics it shows how theories postulating the existence of a new type of force can help explain the properties of dark matter.
“We live in an ocean of dark matter, but we know very little about what it is,” said Flip Tanedo, assistant professor of physics and astronomy and lead author of the study. “This is one of the most annoying unknowns in nature. We know it’s there, but we don’t know how to look for it or why it’s not showing up where we expect it to be.”
Physicists have used telescopes, giant underground experiments, and impactors for the past 30 years to learn more about dark matter, despite the lack of positive evidence. However, negative evidence has forced theoretical physicists like Tanedo to think more creatively about what dark matter is.
Flip Tanedo is Assistant Professor of Physics and Astronomy at UC Riverside. Photo credit: Thomas Wasper
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The new research, which demonstrates an additional dimension in space-time to the search for dark matter, is part of an ongoing research program at UC Riverside led by Tanedo. According to this theory, some particles in dark matter do not behave like particles. In fact, invisible particles interact with more invisible particles so that the latter particle no longer behaves like a particle.
“The goal of my research program over the past two years has been to expand the idea of ’talking’ dark matter with dark powers,” Tanedo said. “In the last ten years, physicists have recognized that in addition to dark matter, hidden dark forces can determine dark matter interactions. It could completely rewrite the rules for searching for dark matter.”
When two dark matter particles are attracted or repelled by each other, the dark forces are at work. Tanedo explains that dark forces are mathematically explained by theories with additional dimensions and appear as a series of puzzle-solving particles seen in small galaxies.
“Our ongoing research program at UCR is another generalization of the Dark Force proposal,” he said. “The universe we observe has three spatial dimensions. We suggest that there may be a fourth dimension known only to the dark forces. Additional dimensions could explain why dark matter hides so well from our efforts to study it in the laboratory.”
The photo shows Flip Tanedo (left), Sylvain Fichet (center) and Hai-Bo Yu. Photo credit: Flip Tanedo, UC Riverside
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Tanedo explains that while additional dimensions may sound like an exotic idea, they are actually a mathematical trick used to describe “conformal field theory” – a very ordinary three-dimensional theory of quantum mechanics. This type of theory is mathematically rich but does not contain conventional particles and so is usually not considered relevant for describing nature. The mathematical equivalence between this advanced three-dimensional theory and the more manageable extra-dimensional theory is known as the holographic principle.
“Because these conformal field theories are persistent and unusual, they are not really applied systematically to dark matter,” Tanedo added. “Instead of using this language, we are working with holographic extradimensional theory.”
The main feature of the extradimensional theory is that the forces between dark matter particles are described by an infinite number of different particles with different masses called a continuum. In contrast, the ordinary force is described by one type of particle with a solid mass. This continuum dark sector class appeals to Tanedo because it makes something “fresh and different”.
According to Tanedo, previous work in the dark sector has mainly focused on theories that mimic the behavior of visible particles. His research program examines a more extreme type of theory that most particle physicists find less attractive, perhaps because there are no real-world analogues.
In Tanedo’s theory, the forces between dark matter particles are surprisingly different from those of ordinary matter.
“With the gravitational force or the electric force that I teach in my introductory physics course, if you double the distance between two particles, the force is reduced by four times. A continuum force, on the other hand, is reduced by a factor of eight.”
What is the effect of this extra-dimensional dark force? Since ordinary matter cannot interact with these dark forces, Tanedo turned to the idea of dark matter interacting on its own, an idea advanced by Hai-Bo Yu, a professor of physics and astronomy at UCR who was not a co-author. article, developed. Yu showed that even without interaction with normal matter, the effects of these dark forces can be observed indirectly in spherical dwarf galaxies. Tanedo’s team found that the continuum force can reproduce the motions of the observed stars.
“Our model goes a step further and makes it easier than a standalone interactive dark matter model to explain the origin of cosmic dark matter,” Tanedo said.
Next, Tanedo’s team will investigate a continuum version of the “dark photon” model.
“It’s a more realistic picture for the dark forces,” Tanedo said. “Dark photons have been studied in great detail, but our extra-dimensional skeleton has some surprises. We will also discuss the cosmology of dark forces and the physics of black holes.”
Tanedo has been working diligently to identify “blind spots” in his team’s dark matter search.
“My research program aims at one of the assumptions we make about particle physics: that particle interactions are best explained by the exchange of more particles,” he said. “While this applies to ordinary matter, there is no reason to think of it as dark matter. Their interactions can be described by a continuum of interchangeable particles, not just one type of particle force exchange.”
Reference: “Continuum-mediated self-interacting dark matter” by Ian Chaffey, Sylvain Fichet, and Philip Tanedo, June 1, 2021, Journal of High Energy Physics.
DOI: 10.1007 / JHEP06 (2021) 008
Tanedo was researched by Ian Chaffey, a postdoctoral fellow who worked with Tanedo; and Sylvain Fichet, postdoctoral fellow at the International Center for Theoretical Physics – South American Institute for Fundamental Research in Brazil.
This research was funded by the US Department of Energy.
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