What is dark matter? How do supermassive black holes actually appear? This old question may be answered by primordial black holes. Cosmologists from Leiden and China have identified a new way through which these hypothetical objects could be born immediately after the Big Bang. Their work has been published in Physical Review Letters.
Scientists are faced with great mysteries in their quest to understand the universe. For example, stars move in galaxies as if they have five times more mass than we see. What does this dark matter include? There is another mystery: galaxies feed huge black holes in their cores, weighing millions of solar masses. In young galaxies, collapsing stars would not have had enough time to expand so much. How did these supermassive black holes form, then?
Primordial black holes: the long-awaited answer?
Cosmologists have proposed a hypothetical solution that could solve one of two mysteries. Primordial black holes, which appeared shortly after the Big Bang, have the ability to either remain tiny or quickly gain mass. In the first case, they are suitable for the role of dark matter. In the second case, they can become seeds for supermassive black holes. Cosmologist Don-Gang Won at the University of Leiden and his Chinese colleagues Yi-Fu Kai, Ji Tong and Sheng-Feng Yang at the University of China have described a new way in which primordial black holes could appear during the Big Bang.
After the Big Bang, the universe contained small density perturbations caused by random quantum fluctuations. They are large enough to form stars and galaxies, but too small to become primordial black holes on their own. Vaughn and his colleagues have identified a new resonant effect that makes primordial black holes possible by selectively amplifying certain disturbances. This leads to the prediction that all primordial black holes should have approximately the same mass. The narrow peaks in the figure show the range of possible masses due to resonance.
“Other calculations increase the resentment differently but run into problems,” Vaughn says. “We use resonance during inflation, when the universe was growing exponentially just after the Big Bang. Our calculations are simple enough to work with. In reality, the mechanism may be more complicated, but this is at least the beginning."
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Ilya Khel