Searching for primitive black holes and dark matter from the "small universe"

 　　The 2020 Nobel Prize in Physics was awarded to three scientists who have made important contributions to the study of black holes. Soon after this, new research findings on black holes appeared in the journal of Science. Scientists discovered that the "small universe" formed during the expansion of the universe was likely to give birth to the most primitive black holes.

　　This series of research was completed by several members of the Kavli Institute of Physics and Mathematics of the University of Tokyo (Kavli IPMU).

　　Dark matter is regarded as the main component of the universe. The gravitational wave signals that people observe and the super-large black holes found in the Milky Way or other galaxies may all originate from dark matter. Before the birth of primordial stars and galaxies, black holes formed in the early universe, and these primordial black holes are likely to be important components of dark matter.

　　In order to study primordial black holes, particle physicists, cosmologists and astronomers from Kavli IPMU formed a research team to start with the early evolution of the universe and find conditions conducive to the formation of black holes.

　　According to the theory of cosmic expansion, during the rapid expansion of the universe, early galaxies and star clusters began to evolve. At the same time, many "small universes" emerged. These vacuum bubbles are likely to be different from the existence of our existing universe. It will collapse, but the huge energy released by the relatively small volume is likely to lead to the production of black holes.

　　For a small universe with a larger volume, if its size is at a certain critical value, according to the theory of relativity, the small universe can be observed from two angles: inside and outside. If it is inside, the observer can see it as an expanding universe, if it is outside, the observer can see it as a black hole. Regardless of the angle, researchers can regard the small universe as the embryonic form of a black hole, which hides the basic structure of multiple universes behind the event horizon.

　　The event horizon is a kind of boundary. What happens inside the horizon cannot affect the outside of the horizon. The periphery of the black hole is the event horizon. The escape speed here is faster than the speed of light, so any object (even light) cannot escape.

　　Previously, the research team had introduced candidate events for primitive black hole observations in journals. In the scientific journal, the research team described a new possibility for the formation of primitive black holes.

　　The research team used the Pleiades Cluster Telescope in Hawaii and its second-generation Hyper Suprime-Cam (HSC) to show the observation data in multiple small universe scenes. If a primordial black hole passes through a stellar galaxy and reaches a star in the line of sight of a telescope, the black hole's gravity will bend the light and make the star brighter than usual in a short period of time. According to the duration of the star's brightening, the mass of the black hole can be measured. With the help of HSC, human beings have the ability to observe hundreds of millions of stars at the same time, so as to "cast a wide net" to find those primitive black holes that are passing through the galaxy.

　　At present, the research team is launching a new round of observations and expanding the scope of the search to further verify relevant conclusions.

　　The research team also showed the HSC observation data, some of which coincide with the rudiments of heavy black holes and supermassive black holes observed by LIGO.

　　A series of numerical studies have shown that if it can be determined that the HSC observation object is the main source of dark matter, then further optical surveys and research can provide more evidence for the formation of primitive black holes.