It’s getting closer: the rotation of black holes could reveal whether dark bosons are present – hypothetical carriers of dark matter. Because their presence should significantly slow down the rotation of the gravitational giants. However, in a preliminary search of 45 pairs of black holes, the researchers found no evidence of the braking effect – this further narrowing the potential masses of these strange bosons.
Scientists are still confused about what kind of particles dark matter is made of. After the long-favorite weakly reactive macromolecules (WIMPSo far no trace has been found, many searches focus on lighter particles, including sterile neutrinos, but also darker bosons such as axions. These strange intermediate particles are said to be billions of times lighter than an electron.
The first indicators of dark bosons could be aberrations Particle collision In accelerators, they are difficult to explain Signals In devices for detecting and distorting dark matter With qualitative leaps Certain atoms.
Braking effect by very light particles
Now researchers have discovered Kwan Yeung Ng from the LIGO Laboratory at MIT and tested another way to check for the presence of dark bosons. Your starting point is a prediction derived from quantum theory. According to this, large amounts of ultra-light particles should originate near the black hole. Their effect then gradually slows the black hole’s rotation through a process called superradiation.
Ng compares this to the circular factor: “If you jump up and down on a carousel, you can draw energy from it – and the bosons do the same thing with a black hole,” the physicist explains. If these dark bosons were present, then we would expect older black holes to spin more slowly than they should due to their mass. Because the bosons must extract energy from it. “
45 pairs of black holes as test objects
Ng and his team have now investigated whether this is the case using 45 pairs of black holes, whose merging has been detected by the gravitational-wave detectors LIGO and Virgo. The mass of the contained black holes, as well as their rotation, can be read from the pattern of spacetime oscillations generated in the process. For each black hole, the team examined whether the rotational velocity matched that of their mass model.
“If there were dark bosons, they would have swallowed up a large chunk of the angular momentum – they really are like vampires,” says fellow Ngo Salvatore Vitali. Physicists estimate that a super-radian could reduce the rotation of a black hole by up to half as a result of these strange particles.
There is no indication that the rotation is slowing down
But when the team evaluated their data, there was no evidence of such a braking effect – on the contrary: in two pairs, GW190412 and GW190517, the rotational velocities of black holes were close to the physical maximum of objects by their mass. This indicates that, at least in the vicinity of these two black holes, there are not significant quantities of dark bosons.
“The black holes observed by LIGO and Virgo speak strongly against the existence of ultralight scalar bosons,” says Ng and his team. It cannot be excluded that the accumulation of matter accelerated black holes and thus masked the suppressive effect of the bosons. But the timing of the objects we’re observing now isn’t correct: “It would have taken a long time to accelerate the black hole to the level we see here,” says Ng.
The mass range of dark bosons is shrinking
According to the researchers, their results indicate that dark bosons with at least a certain mass range are highly unlikely. This exclusion range ranges from 1.3 x 10-13 And 2.7 x 10 -13 Electron volts, as physicists have determined based on the masses of their black holes. This narrows the area in which one has to look for the darker bosons more.
However, this does not yet mean that dark bosons do not exist: “There are different types of bosons and we have now examined one of them,” Vitaly confirms. “But there could be others. So we want to extend these analyzes to the datasets that LIGO and Virgo will collect in the next few years.”
Remarkably lighter bosons can be detected, for example, by the spin of heavier black holes. For example, rotation measurements of supermassive black holes in the core of galaxies can lead to a boson mass range of up to 10.-21 Are being examined. (Letters of Physical Review, 2021; Doi: 10.1103 / PhysRevLett.126.151102)
Coyle: Massachusetts Institute of Technology (MIT)