The study suggests that dark matter could contain an invisible ‘periodic table’, but it remains elusive
When delving into the mysterious world of theoretical physics, one of the most difficult concepts for scientists to explain is that of dark matter. It is the invisible form of matter that always eludes scientific proof, and whose existence is only suggested by the circumstantial evidence that we can measure about it. It does not react to light, it is literally “dark”.
Although dark matter may seem mysterious, most scientific theories assume that its components are very basic — just a single, exotic, lightweight particle found throughout the universe, which rarely touches other types of matter. But all this may now be up for debate.
A recent study published on the preprint database arXiv has thrown the theoretical simplicity of dark matter out the window by researchers who may have already figured out how to generate massive dark matter particles. They suggest that these particles are not lightweight at all and could come in all sorts of ‘species’ – with their own ‘dark matter periodic table’ of invisible elements, originally forming shortly after the Big Bang after being trapped in black holes. They call this process “recycling.”
Although the theory proposed by the researcher may be exciting, the problem of actually detecting these particles remains the most pressing question and may still be an obstacle for cosmologists. The key to this discovery may lie in understanding how dark matter formed historically.
“The formation history of dark matter itself is much more complex. This is the challenge for astronomers like me,” said Henk Hoekstra, professor of cosmology from Leiden University. “Many different ideas for dark matter lead to features that are practically indistinguishable, and may be Only direct detection experiments can tell the difference. This paper now suggests that the formation process may be more complex, which may in turn expand detection possibilities.
“Many different ideas of dark matter lead to practically indistinguishable features, and only direct detection experiments may be able to tell the difference.”
The change in mass in the new theory also links dark matter and black hole formation closely, from previous assumptions that all dark matter particles are lightweight (known as WIMPs, or weakly interacting massive particles) to the possibility that some are very heavy. It is now more widely understood that when the fundamental forces of nature began to split apart from each other during the Big Bang—creating gravity, electromagnetism, the strong nuclear force, and the weak nuclear force—this split was not straightforward, but involved some states in transition.
As LiveScience’s Paul Sutter succinctly explains, fundamental physics changes at each of these transitional phases, and so there will be pockets of the universe where some of the old physics still applies even though the rest of the universe around it has changed — like how bubbles in water change. Boiling There are trapped pockets of transitional air.
Want more health and science stories in your inbox? Sign up for the weekly Salon Lab Notes newsletter.
The researchers suggest that in these pockets of transitional physics, lightweight dark matter particles could have been trapped, until they became so heavy that they collapsed into black holes before evaporating through radiation.
While the idea of these heavier particles may seem to suggest that they are easier for scientists to find, this may not actually be the case, and a larger particle may not necessarily help observation efforts either. This difference could eliminate new detection possibilities, noted Ludovic van Werbeke of the University of British Columbia.
“The model proposed in this paper assumes the existence of very massive dark matter particles. There are actually very many of them, but because their mass is greater than that of inert particles, their number density is also very low – much lower than the number density of massive particles, so they will escape detection.” Also direct.
If there really are a host of new types of particles, does that also mean that there could be a whole set of currently undiscovered laws of physics, working silently all the time?
However, the problem of actually detecting dark matter particles is not something every new model of dark matter seeks to solve. This type of approach – commonly known as an ad hoc approach to scientific theory – may have its limitations, but it has also been fundamental to exploring the basic assumptions in the field to date.
“It’s not a criticism. It’s a general feature of dark matter models outside the scope of WIMPs,” Van Waerbeke said. “They assume a kind of ‘dark sector’ based on hypothetical dark matter physics, but it has no direct observational motivation.”
However, beneath the new theory’s assumptions is a larger question that could play a role in the quest to prove the existence of dark matter: if there are indeed a host of new particle types, does that also mean there could be a full host? To the currently undiscovered laws of physics, which have been working silently all this time? If so, it could form a periodic table, much like ours, that atlas of all known matter that includes everything from hydrogen to oganessone.
“It’s hard to know, because the paper doesn’t explore the astrophysical consequences of the model,” Van Weerbeke said. “What comes to mind is a possible observational signature of continuous injection of photons throughout the history of the universe.”
In other words, it’s a question of “whether it could affect the physics of the cosmic microwave background or later, during the formation of the first stars — the so-called cosmic dawn,” Van Waerbeke said.
This history, as Hoekstra points out, can become more complex to understand through the lens of new theory. However, there are likely to be limits to the theory’s implications for the laws of physics as we understand them.
“The described process only occurred at the beginning of the universe, so it does not change anything today,” Hoekstra said. “However, invisible physics is at work right under our noses, because dark matter is flying through our bodies all the time.”