Shock waves in the early universe may have helped matter reign supreme
DENVER — Tiny, exploding black holes could explain one of the biggest mysteries about how the universe, in its current form, came to be.
In the cosmos, matter is much more widespread than antimatter. But scientists don’t know how matter gained its dominance. Now a team of physicists report that the takeover of matter could involve tiny black holes, born in the first moments after the Big Bang. These hypotheticals primordial black holes would have quickly evaporated and exploded, sending shock waves outwards. This could have prepare the ground that matter takes over, physicist Alexandra Klipfel reported in March at the American Physical Society’s World Physics Summit.
Scientists believe that the universe was formed with equal amounts of matter and antimatter. But matter and antimatter annihilate when they meet. Without something to tip the balance, the universe would have been featureless, containing pure energy. Tiny black holes could have shifted the balance to produce our matter-rich cosmos, allowing the formation of stars, planets and galaxies within it.
If true, it would give scientists insight into black holes that would otherwise be very difficult to study, says theoretical physicist Lucien Heurtier of King’s College London, who was not involved in the research. “It’s very difficult to detect their existence in cosmology because they are extinct. They have been extinct for some time.”
Black holes are thought to have formed from fluctuations in the density of the early universe, with a mass of about a thousand kilograms each, or about that of a small car. These relatively small black holes would have lived and died in the mud of the early universe called the quark-gluon plasmathe phase of matter that existed before the formation of protons and neutrons. They would have spewed energetic particles — a phenomenon called Hawking radiation — thus warming their environment.
A radiant black hole would have gradually lost mass before dying out in the first tenth of a billionth of a second of the existence of the universe. Such an explosion would have triggered a shock wave in quark-gluon plasma, the researchers report in a related paper submitted March 16 to arXiv.org. The sudden explosion would have injected a large amount of energy into the plasma. “And that heats a little sphere of our plasma, very, very hot,” says Klipfel. “It’s a very sharp wall,” with different conditions inside and outside the shock.
Such a sharp wall would provide the necessary conditions for create excess materialreport the researchers in another article submitted March 30 to arXiv.org. If everything in the universe were evenly distributed and balanced, any conversion process between matter and antimatter would work in both directions at once, resulting in no excess matter or antimatter. But conditions on one side of the shock wave would be radically different from those on the other, in a way that could give matter a boost.
Inside a thin shell surrounding such a shock wave, temperatures would be so high that the particles would have no mass. This is because the Higgs mechanism, the phenomenon associated with Higgs boson which gives mass to the particles, only occurs below a certain temperature.
Apart from such a shock wave, the particles would have mass. This means that when particles cross the boundary, their mass changes. This, combined with other physical effects thought to be present in the early universe, could have caused excess matter to accumulate at the edge of a shock wave. This excess material could then have been trapped as the shock spread.
For primordial black holes to be responsible for anchoring matter, a multitude of them would have had to explode moments after the Big Bang. Instead of being a finale, these fireworks could have been just the beginning.
