Fast spinning black holes can search for dark material

(Credit: Robin Dienel / Carnegie Institution for Science)We are constantly learning new things about the universe, but the more we know, the clearer it becomes that you are missing pieces of the puzzle. The possible existence of dark matter is one of the more disturbing pieces missing, but a team from MIT thinks that fast-rotating black holes can help curb the search for these mysterious particles.

The matter we can see in the universe makes up only 15 percent of us think is there based on the rate of expansion. This missing mass is known as dark matter, and there are numerous ideas about what it is and how we can find it. One of the more popular suspects is a theoretical particle called an ultralight boson. If they exist, ultra-light bosons will be so small that they interact with almost nothing else in the universe – except perhaps certain black holes.

Quantum theory predicts that objects on a very small scale such as the ultralight boson do not work in the same way as larger ones, which obeys classical physics. We do not know how small the ultralight boson is, but as the name suggests, it is small. This means that it must have a Compton wavelength, which is inversely proportional to its mass. Therefore, an ultralight boson has an extremely long wavelength that can overlap with certain black holes. This will cause the particles around the black hole to accumulate and slow down the rotation rate. If there is no slowdown, the range of masses where the ultralight boson can exist is reduced.

The team from MIT’s LIGO laboratory went in search of black holes that would fit the bill to test this hypothesis. LIGO, the Laser Interferometer Gravitational-Wave Observatory, is capable of listening to gravitational waves propagating from distant sources, such as black hole binaries. The team looked at all 45 black hole binaries identified by LIGO and its companion project, Virgo. They pulled in two, known as GW190412 and GW190517.

Both of these objects were found to rotate at their maximum speed, which would predict the established physics. This means that the ultralight boson cannot exist between 1 × 10 ^ -13 and 2 × 10 ^ -11 electron volts. Otherwise, ultralight forest zones around the black holes will begin to accumulate, subtracting about half of their rotational energy. No sluggish black holes, no ultralight woods.

This does not mean that the ultralight boson is a fantasy. It just means that it does not exist in this mass series. Experiments from the past could exclude the particle in small shots of space, but it is a large piece that researchers could possibly discount in their search for dark matter. Of course, other teams will have to confirm the finding. This work also shows that tools such as LIGO can be useful in the search for exotic particles.

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