Back in the 70s of the last century, the physicists announced problems in the standard model of elementary particle science. This theory describes three fundamental forces of nature. And although the theory suggests that symmetry is broken between particles and forces in the Universe, just as in the mirror version, the experiments suggest otherwise. This discrepancy is called the strong CP problem, where CP stands for charge combined with parity.
In electromagnetic interaction, this theory is consistent with observations. But in the case of strong interactions, a problem arises, since the theory admits violations of the combined symmetry operation CP for both weak and strong interactions.
Such cases are one in a thousand, and many scientists predicted them before. In attempts to find CP violations, no effect was achieved. Theoretical physicists Roberto Peccei and Helen Quinn proposed a possible solution. Their hypothesis is related to a new symmetry that suppresses SR participants, forcing them to match observations. As a result, a completely new particle was identified, it was the axion. It should be very light and free of charge.
Due to these characteristics, the axion is one of the most obvious contenders for dark matter. The fact that dark matter can be composed of axions could be one of the greatest achievements of science.
Axions can have another extremely important property, it is associated with the fact that next to the electromagnetic field, they can easily turn into photons that can be detected. To capture them, high concentrations of axions and strong magnetic fields are needed.
The experts at the Kavli Institute of Physics and Mathematics of the Universe suggested that dark matter can be found near neutron stars - it surrounds them. To do this, they proposed using radio telescopes - the Robert C. Byrd Green Bank telescope in the USA and the 100-meter Effelsberg radio telescope in Germany.
They both target the closest neutron stars to the Earth, which have strong magnetic fields. The physicists were able to study their radio frequencies in the 1 GHz range, which corresponds to the masses of axions. So far, no signals were received, they will continue the research in the near future.