In the first moments after the Big Bang, matter and antimatter were almost perfectly balanced. But something tipped the scales — otherwise everything would have annihilated into radiation, leaving the universe empty. One candidate for the role of "tipper" is the ultraheavy right-handed neutrino. These are twin particles of ordinary neutrinos, only billions of times more massive. The problem is that in the hot early universe, producing them in sufficient quantities is tricky.
The authors propose an unexpected source: primordial black holes. These are tiny objects that could have formed from clumps of superdense matter in the first instants. Such a hole, with the mass of an asteroid, evaporates via Hawking radiation — a stream of particles that escapes from the black hole due to quantum effects at the horizon. This stream includes the sought-after neutrinos. From there, it's like a chain reaction: the neutrinos decay, creating an excess of matter, and also emit gravitational waves — ripples in spacetime itself.
The most intriguing part is the gravitational "trace." Such an event leaves not one but several peaks at different frequencies: from neutrino decay, from the hole's evaporation itself, and from the inhomogeneities it created in space. These frequencies range from megahertz to exahertz — currently beyond the reach of existing detectors. But technology is advancing, and a multifrequency signal could be a true "gold mine" for future observatories.
Thus, tiny black holes, evaporating without a trace, could leave behind a symphony of gravitational waves, and the key to one of cosmology's greatest mysteries.
Primordial black holes, if they exist, could be the size of an atomic nucleus but weigh as much as a mountain.
In Robert Forward's novel "Dragon's Egg," life on a neutron star is depicted — here, tiny black holes become "factories" for producing matter.