At the dawn of time: MIT physicists link dark matter to ‘supercharged’ microscopic black holes

According to the researchers, the universe could have produced microscopic black holes with enormous amounts of nuclear charge in the first quintillionth of a second. MIT physicists.

MIT researchers say primordial black holes, possibly a form of dark matter, may have formed in the first moments after the explosion. Big bang and carried high levels of a nuclear property known as color charge. These supercharged black holes, despite their short existence, may have influenced the cosmology of the early universe and could explain a number of astronomical phenomena observed today.

Dark matter and primordial black holes

For every kilogram of matter we can see – from the phone in your hand to distant stars and galaxies – there is 5 kilograms of invisible matter permeating our environment. This ‘dark matter’ is a mysterious entity that evades all forms of direct observation and yet makes its presence felt through its invisible attraction to visible objects.

Fifty years ago, physicist Stephen Hawking proposed an idea of ​​what dark matter might be: a population of black holes, which might have formed very soon after the Big Bang. Such “primordial” black holes would not have been the goliaths we observe today, but rather microscopic regions of ultra-dense matter that would have formed in the first quintillionth of a second after the Big Bang and then collapsed and spread over would spread across the cosmos as they dragged along. that line space-time in ways that could explain the dark matter we know today.

Uncovering supercharged black holes

Now MIT physicists have discovered that this original process would also have produced some unexpected companions: even smaller black holes with unprecedented amounts of a nuclear physical property known as “color charge.”

These smallest, “supercharged” black holes would have been an entirely new state of matter, likely evaporating a fraction of a second after they emerged. Yet they could still have influenced an important cosmological transition: the time when the first atomic nuclei were forged. The physicists hypothesize that the color-charged black holes may have affected the balance of merging nuclei in ways that astronomers might one day discover with future measurements. Such an observation would convincingly point to primordial black holes as the root of all modern-day dark matter.

“Even if these short-lived, exotic creatures no longer exist today, they could have influenced cosmic history in ways that could be reflected in subtle signals today,” said David Kaiser, professor of history of the universe. sciences in Germeshausen and professor of physics at New York University. MIT. “Given the idea that all dark matter can be explained by black holes, this gives us new things to look for.”

Kaiser and his co-author, MIT student Elba Alonso-Monsalve, published their research June 6 in the journal Physical Assessment Letters.

A time before the stars

The black holes we know and observe today are the product of stellar collapse, where the center of a massive star collapses in on itself, forming a region so dense that it can bend space-time in such a way that everything – even light – gets stuck in it. . Such ‘astrophysical’ black holes can be a few times as massive as the Sun to many billions of times as massive.

‘Primitive’ black holes, on the other hand, may be much smaller and are thought to have formed at a time before stars. Before the universe had even conceived of its basic elements, let alone stars, scientists believe that regions of ultra-dense, primordial matter could have accumulated and collapsed to form microscopic black holes that could have been so dense that they could have reached the mass of a could squeeze an asteroid into space. region as small as a single one atom. The gravity of these small, invisible objects scattered across the universe could explain all the dark matter we can’t see today.

If that were the case, what would these primordial black holes be made of? That is the question Kaiser and Alonso-Monsalve asked themselves with their new research.

“People have studied its distribution black hole “There would have been loads of masses during this production from the early universe, but no connection has ever been made to what kinds of things would have fallen into those black holes at the time they formed,” Kaiser explains.

Supercharged rhinos

The MIT physicists first looked at the likely distribution of the masses of black holes as they first formed in the early universe through existing theories.

“Our realization was that there is a direct correlation between the time at which a primordial black hole forms and the mass with which it forms,” says Alonso-Monsalve. “And that time frame is absurdly early.”

She and Kaiser calculated that primordial black holes must have formed within the first quintillionth of a second after the Big Bang. This time flash would have produced ‘typical’ microscopic black holes as massive as an asteroid and as small as an atom. It would also have produced a small fraction of exponentially smaller black holes, with the mass of a rhinoceros and a size much smaller than a single proton.

What would these primordial black holes be made of? To do this, they looked at studies that investigate the composition of the early universe, and specifically at the theory of quantum chromodynamics (QCD) – the study of how quarks and gluons interact.

Quantum dynamics and black hole formation

Quarks and gluons are the fundamental building blocks of protons and neutrons – elementary particles that together form the basic elements of the periodic table. Immediately after the Big Bang, physicists estimated, based on QCD, that the universe was extremely hot plasma of quarks and gluons that then cooled rapidly and combined to produce protons and neutrons.

The researchers found that within the first quintillionth of a second, the universe would still have been a soup of free quarks and gluons that had yet to be combined. Any black holes that formed during this time would have swallowed up the loose particles, along with an exotic property known as ‘color charge’ – a charge state that only uncombined quarks and gluons carry.

The role of color charge in black hole dynamics

“Once we discovered that these black holes form in a quark-gluon plasma, the most important thing we had to figure out was: How much color charge is in the blob of matter that will end up in a primordial black hole?” says Alonso-Monsalve.

Using QCD theory, they calculated the color charge distribution that should have existed in the hot, early plasma. They then compared that to the size of an area that would collapse to form a black hole in the first quintillionth of a second. It turns out that most typical black holes would not have had much color charge present in them at that time, because they would have been formed by absorbing a large number of regions containing a mix of charges, ultimately resulting in a ‘neutral’ core. ” attack.

Conclusion and future implications

But the smallest black holes would be packed with color charge. In fact, they would contain the maximum amount of charge allowed for a black hole, according to the fundamental laws of physics. While such “extreme” black holes have been hypothesized for decades, until now no one had discovered a realistic process by which such oddities could actually have formed in our universe.

Professor Bernard Carr of Queen Mary University of London, an expert on primordial black holes who first worked on the subject with Stephen Hawking, describes the new work as ‘exciting’. Carr, who was not involved in the research, says the work “demonstrates that there are circumstances in which a small fraction of the early universe could invade objects with an enormous amount of color charge (at least for a while), exponentially greater than what has been identified in previous studies on QCD.”

The supercharged black holes would have evaporated quickly, but possibly only after the first atomic nuclei began to form. Scientists estimate that this process began about a second after the Big Bang, which would have given extreme black holes enough time to disrupt the equilibrium conditions that would have prevailed when the first nuclei began to form. Such disruptions could potentially influence how these earliest nuclei formed, in ways that might one day be observed.

“These objects may have left some exciting observational impressions,” Alonso-Monsalve muses. “They could have changed the balance between this and that, and that’s something you can wonder about.”

Reference: “Primordial black holes with QCD color charge” by Elba Alonso-Monsalve and David I. Kaiser, June 6, 2024, Physical Assessment Letters.
DOI: 10.1103/PhysRevLett.132.231402

This research was supported in part by the U.S. Department of Energy. Alonso-Monsalve is also supported by a grant from the MIT Department of Physics.