Unveiling the Mysteries of Primordial Black Holes: Could They Be Dark Matter Candidates?

Recent research has shed new light on the intriguing possibility that primordial black holes could serve as candidates for dark matter, particularly those exhibiting peculiar nuclear physics properties known as color charge. These primordial black holes, believed to have formed in the early stages of the universe post-Big Bang, may have left subtle traces in the cosmos, potentially influencing the abundance of cosmic elements. The enigmatic connection between primordial black holes and dark matter opens up a realm of exploration into the fundamental mysteries of the universe, offering a glimpse into the intricate interplay of cosmic forces and the enigmatic nature of dark matter.

From the cell phone in front of you to distant stars and galaxies, all matter we see is ordinary matter. However, astronomical observations show that in addition to these visible matter, there is also a large amount of invisible dark matter in the universe. But the exact nature of dark matter remains an unsolved mystery.

Fifty years ago, Hawking proposed the possibility that dark matter might be black holes. This hypothetical black hole, called a primordial black hole, was formed by the gravitational collapse of a dense region of the universe after the Big Bang. Observations show that if primordial black holes are to be used to fully explain dark matter, these black holes would have to be very light, perhaps less massive than a small asteroid. Specifically, primordial black holes weighing between 10¹⁷ and 10²² grams remain viable candidates.

Recently, in a new study published in Physical Review Letters, physicists discovered that some smaller primordial black holes possess a strange nuclear physics property-color charge. Such primordial black holes may leave behind potentially observable signatures.

Back to a time before stars formed

At present, astronomers have discovered many black holes. Some of them are stellar black holes formed by the collapse of massive stars at the end of their lives. Some are supermassive black holes in the centers of galaxies – these black holes have a mass of millions of the sun. Times, even billions of times.

In comparison, primordial black holes are much smaller, and they formed much earlier than stars. They are going back to the very beginning of the universe. Physicists estimate that the universe after the Big Bang was an extremely hot plasma composed of elementary particles called quarks and gluons, like a bowl of “hot quark and gluon soup.” These free particles then rapidly cooled and combined to create the protons and neutrons that make up the basic elements. And it was before the universe even gave birth to basic elements that ultra-dense primordial matter would accumulate and collapse to form primordial black holes.

Colored primordial black hole

In the study, scientists first used existing theories to study the possible distribution of black hole mass when it was formed in the early universe. They realized that there was a direct correlation between the time of formation and the mass of the primordial black hole. This time window is very early. They calculated that primordial black holes must have formed within the first 10¹⁸ of a second after the Big Bang, that is, they formed in a hot quark-gluon plasma.

These black holes eat up unconstrained particles and have a peculiar property called color charge, a charge carried by unbound quarks and gluons. Researchers realized that if they want to know the composition of a black hole, they must figure out how many color charges are contained in the mass of matter from which the original black hole was formed.

Using quantum chromodynamics (QCD) theory, which studies the interaction of quarks and gluons, they calculated the color charge distribution that should have existed in the hot early plasma and compared the results with the collapse to form a black hole in the first 10¹⁸seconds The area sizes were compared.

They found that this moment would create a “classic” primordial black hole, which is as massive as an asteroid and only as large as an atom. Most “typical” black holes don’t have much color charge in them because they are formed by absorbing a large mix of charges, which eventually “cancel out” to neutrality.

However, they also found that this process should also produce a small number of much smaller primordial black holes, with a mass about the same as a rhinoceros and a volume much smaller than a proton. These smallest black holes are filled with color charges. In fact, according to the basic laws of physics, they contain as much charge of any type as a black hole can allow. Such “supercharged” black holes have been hypothesized mathematically for decades, but the process that creates this strange phenomenon in the universe has never been discovered.

Subtle traces

Presumably, supercharged black holes evaporate rapidly. Although these fleeting, exotic objects no longer exist, they may have altered the history of the universe in some way, affecting a key cosmic transition: when the earliest atomic nuclei formed.

Scientists estimate that supercharged black holes may not disappear until the first nuclei begin to form. They have enough time to break the equilibrium conditions at that time, disrupt the distribution of protons and neutrons, and thus leave subtle changes in the abundance of elements in the universe. trace. Such imprints may one day be observed. This also provides astronomers with new search objects.

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