by The hunt for tiny black holes left over from the Big Bang may be about to heat up.
Just as the track for such small black holes seemed to be cold, an international team of scientists in quantum physics has found clues that could reopen the case. One reason so-called primordial black holes are so urgent is that they have been proposed as potential candidates for dark matter.
Dark matter makes up 85% of the mass in the universe, but it doesn’t interact with light like normal matter does. It is the matter made up of atoms that comprise the stars, planets, moons and our bodies. Dark matter interacts with gravity, however, and this effect is possible affect “ordinary matter” and light. Perfect for Cosmic detective work.
If there are Big Bang-triggered black holes out there, they would be extremely small – some could be as small as a dime – and therefore would have masses equivalent to asteroids or planets. Still, like their larger counterparts, there are stellar mass black holes, which can have masses 10s to 100s more than the Sun, and supermassive black holes, which can be millions or even billions of times more massive. have the sun, small black holes from which the light-trapping surface would be called “the event horizon.” The event horizon prevents black holes from emitting or reflecting light — making primordial black holes a solid candidate for dark matter. They can be small enough to go unnoticed, but strong enough to affect a space.
Related: The small black holes left over from the Big Bang may be suspected of being dark matter
The team of scientists — from the Research Center for the Early Universe (RESCEU) and the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU, WPI) at the University of Tokyo — implemented a theoretical framework that combines classical field theory, Einstein’s specialty. relativity theory, and quantum mechanics to the early universe. The latter accounts for the behavior of particles such as electrons and quarks and gives rise to quantum field theory (QFT).
Applying QFT to the infant cosmos, the team believed that there are far fewer hypothetical black holes in the universe than many models currently estimate. If this is the case, it may rule out primordial black holes because dark matter is suspect.
“We call them primordial black holes, and many researchers feel they are a strong candidate for dark matter, but they would need a lot to satisfy that theory,” University of Tokyo graduate student Jason Kristiano said in statement. “They are interesting for other reasons, too, because since the recent innovation of gravitational wave astronomy, there have been discoveries of binary black hole mergers, which can be explained by the existence of a large number of primordial black holes.
“But despite these strong reasons for its expected abundance, we haven’t seen any directly, and now we have a model that should explain why this is so.”
Back to the Big Bang to hunt for primordial black holes
The most favored cosmological models suggest that the Universe began about 13.8 billion years ago during an initial period of rapid inflation: the Big Bang.
After the first particles emerged in the universe during this initial expansion, space eventually became cool enough to allow electrons and protons to bond and form the first atoms. That’s when the element hydrogen was born. Furthermore, before that cooling occurred, light could not travel through the cosmos. That’s because electrons endlessly scatter photons, which are particles of light. Thus, during these dark literary ages, the universe was essentially opaque.
Once the free electrons, however, were able to bond with protons and stop bouncing around, light could finally travel freely. After this event, called the “last dispersion,” and during the following period known as the “Age of reionization,” the universe immediately became transparent. The first light can be seen throughout the globe at this time still visible today as. a largely uniform field of radiation, a universal “fossil” known as the “Cosmic Microwave Background” or “CMB.”
Meanwhile, the hydrogen atoms that were created formed the first stars, the first galaxies and the first clusters of galaxies. And, sure enough, some galaxies appeared to have more mass than their visible constituents could account for, and this excess was attributed to any other dark matter.
While stellar mass black holes arise from the collapse and death of massive stars, and supermassive black holes grow from the successive mergers of smaller black holes, primordial black holes predate stars – therefore, they must have a unique origin. .
Some scientists think that conditions in the early universe were so hot and dense that smaller patches of matter could collapse under their own gravity to give birth to these tiny black holes — with an event horizon no wider than a dime, or b ‘maybe even less than a proton, depending on. their mass.
The team behind this research had previously looked at models of primordial black holes in the early universe, but these models did not match the CMB observations. To correct this, the scientists applied corrections to the initial theory of the creation of a primordial black hole. Corrections reported by QFT.
“At the beginning, the universe was extremely small, much smaller than the size of a single atom. Cosmic inflation expanded that quickly by 25 orders of magnitude,” Kavli IPMU and RESCEU director Jun’ichi Yokoyama said in the statement. “At that time, waves traveling through this tiny space could have relatively large amplitudes but very short wavelengths.”
The team discovered that these tiny but strong waves can undergo amplification to become the much larger and longer waves that astronomers see in today’s CMB. The team thinks that this amplification is the result of coherence between the early short waves, which can be explained using QFT.
“While individual short waves would be relatively powerless, coherent groups of waves would have the power to reshape much larger than themselves,” Yokoyama said. “This is a rare case where a theory about something on a large scale seems to explain something on the other end of the scale.”
If the team’s theory that early-scale fluctuations in the universe can grow and influence large-scale fluctuations in the CMB is correct, this will have an impact on how structures in the cosmos grew. Measuring the CMB fluctuations may help to constrain the magnitude of the original fluctuations in the early universe. This, in turn, places constraints on phenomena that rely on shorter fluctuations, such as primordial black holes.
“Primordial black holes are widely believed to be the collapse of short but strong wavelengths early in the universe,” said Kristiano. “Our study suggests that there should be far fewer primordial black holes than expected if they are indeed strong candidates for dark matter or gravitational wave events.”
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Primordial black holes are firmly hypothetical at the moment. That’s because even the much larger objects are hard to see due to the light-trapping nature of stellar-mass black holes, so imagine how hard it would be to see a black hole with an exit horizon the size of a dime .
The key to detecting primordial black holes may lie not in “traditional astronomy,” but in the measurement of tiny vibrations in spacetime called gravitational waves. Although current gravitational wave detectors are not sensitive enough to detect leaks in spacetime from primordial black holes, future projects, such as the Laser Interferometer Space Antenna (LISA), will bring gravitational wave detection to space. This could help confirm or deny the team’s theory, bringing scientists closer to confirming whether primordial black holes could account for dark matter.
The team’s research was published on Wednesday (May 29) in the journal Physical Review Letters.
RELATED STORIES
— Dark matter was detected hanging from the cosmic web for the 1st time
— How the successor to the Large Hadron Collider will pursue the dark universe
– A massive galaxy is a cosmic puzzle with no dark matter
RELATED STORIES
— Dark matter was detected hanging from the cosmic web for the 1st time
— How the successor to the Large Hadron Collider will pursue the dark universe
– A massive galaxy is a cosmic puzzle with no dark matter
