Scientists may have found an explanation for why primordial black holes, thought to have formed shortly after the Big Bang, have not been directly observed. A new study suggests there may be far fewer of these miniature black holes than previously believed. Primordial black holes are considered a strong candidate for dark matter, the mysterious substance that makes up over 85% of the universe’s mass.
However, despite their expected abundance, astronomers have not been able to detect any directly. “Many researchers feel they are a strong candidate for dark matter, but there would need to be plenty of them to satisfy that theory,” said Jason Kristiano, coauthor of the study and a graduate student at the University of Tokyo. The researchers applied current understandings of quantum field theory to observations of the cosmic microwave background (CMB), the remnants of the oldest light in the universe.
Fewer primordial black holes detected
They posit that the gravitational waves responsible for creating primordial black holes may not have been as numerous as previously thought. “What we have found is that these tiny but strong waves can translate to otherwise inexplicable amplification of much longer waves we see in the present CMB,” said coauthor Jun’ichi Yokoyama at the University of Tokyo’s Kavli Institute for the Physics and Mathematics of the Universe.
The study suggests that while individual short waves would be relatively powerless, coherent groups would have the power to reshape much larger waves. This could explain the lower numbers of primordial black holes. To confirm their theory, the researchers will look to future hyper-sensitive gravitational wave detectors such as the Laser Interferometer Space Antenna (LISA) project, set to launch in 2035.
The findings, published in the journal Physical Review Letters, could significantly impact our understanding of the early universe and the nature of dark matter. However, more definitive answers will require advanced observational tools in space.
