Scientists have found evidence in favor of the fact that dark matter consists of ultralight particles — axions. Thanks to this, they managed to link this mysterious type of matter with the problem of the “clumpiness” of the Universe, more precisely, why it is relatively uniform.
Problem of the “clumpiness” of the Universe
A group of scientists from the University of Toronto has recently published a theoretical paper, which they call “breakthrough” and in it they prove that dark matter consists of ultralight particles — axions. Thanks to this, they can solve the system with the “clumpiness” of the Universe.
The problem with it is not that there are some abnormally large clumps of matter in the Universe. On the contrary, the Universe looks too homogeneous when compared with what people know about the presence of ordinary and dark matter in it.
Galaxies form a “cosmic web”, but the nodes in it, which are superclusters, are relatively small. If dark matter consisted of some heavy particles, then the “clumpiness” on a large scale would have to be much larger.
Dark matter can consist of axions
In order to prove their point, the scientists examined the remnants of light from the Big Bang, that are known as background microwave radiation. Next, they used a sky survey known as the Baryon Oscillation Spectroscopic Survey (BOSS); it contains data on the exact location of about a million galaxies.
Finally, they modeled what the distribution of galaxies and the relic radiation would be like if dark matter consisted of very light particles, which corresponded to extremely long waves, and they completely coincided with what observers saw.
This is what we would observe if dark matter consisted of axions. Physicists describe these particles as “fuzzy” due to the fact that they exhibit wave properties much more than other “units of matter”. The waves that correspond to them may have a length comparable to the size of galaxies, and this may explain why the Universe is so uniform.
Not everything is so clear
The published work should be considered in the context of the fact that a heated discussion about the essence of dark matter has been going on between scientists for several years. A small number of researchers deny its existence at all. The rest put forward theories that contradict each other and publish articles with evidence in support of them.
For example, a number of articles have recently been published that dark matter can form huge Q-balls inside galaxies, or even individual stars and planets. But those constructions are based on concepts that directly contradict what the authors of the theory of “axions” describe.
Currently, scientists do not have a unified theory that would simultaneously explain gravity and quantum mechanics, the so-called “theory of everything”. The most popular candidate for this role over the past few decades is string theory, which claims another level, below quantum, where everything consists of string-like excitations of energy. According to Keir Rogers, one of the authors of the current study, the detection of a fuzzy axon particle may be a hint that string theory is correct.
“We have the tools now that could enable us to finally understand something experimentally about the century-old mystery of dark matter, even in the next decade or so—and that could give us hints to answers about even bigger theoretical questions,” says Rogers. “The hope is that the puzzling elements of the universe are solvable.”
According to phys.org
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