New theory suggests that cosmic bubbles may have created dark matter

 According to foreign media(replica hermes) reports, a new study shows that the cosmic bubbles that expanded in our early universe may have created a large amount of dark matter. This elusive substance will pull the star, but it will not emit light.

　　 This new research was published in the October 9th issue of Physical Review Letters. New research may exactly explain the way dark matter condenses from the hot soup of the early universe. Since the astronomer Fritz Zwicky first proposed the existence of dark matter in 1933, a large amount of observational evidence has shown that something is hidden in the dark, not only invisible to the naked eye, but also invisible to even the most advanced scientific instruments. We can only find clues about dark matter from the gravitational pull exerted by dark matter on the stars and galaxies that astronomers can observe. The magnitude of this gravity allows scientists to estimate the percentage of dark matter in the universe; current estimates show that dark matter accounts for 80% of the universe's mass.

Andrew Long, co-author of the study and assistant professor of physics at Rice University in Houston, said: "Although we know how much dark matter is contained in the universe, for decades, we have not known the nature and source of dark matter. Dark matter is a collection of elementary particles. Is it? If so, what are the properties of these particles? For example, their mass and spin? What force will these particles exert, and what kind of interactions exist between them? When did dark matter form? In their formation In the process, what important role did the interaction play?"

　　 Michael Baker, a physicist at the University of Melbourne, Australia, Joachim Kopp, a physicist at the University of Mainz, Germany, and Lang, hope to answer this last question-when and how dark matter was formed. Lang said that they studied the earliest period of the formation of the universe, that is, less than a nanosecond after the start of the Big Bang, which is the "Wild West" time of particle formation and annihilation. During this period, the particles collide and annihilate as soon as they are formed. At that time, the universe was a hot soup of extremely high-energy elementary particles, similar to the quark-gluon plasma produced by today's physicists in large particle accelerators. This primordial soup is extremely hot, dense and chaotic, and more ordered subatomic particles such as protons and neutrons cannot be formed.

　　 But the "Wild West" era of this universe did not last long. After the universe began to expand, the plasma gradually cooled, and the production of new particles stopped abruptly. At the same time, the particles separated from each other, and the collision speed dropped suddenly until the number of particles remained constant. Scientists refer to the remaining particles as "thermal residual particles." These thermal surviving particles then became the matter we know and love today, such as atoms, stars, and even ourselves. "In addition to all the elementary particles known today, we have reason to imagine that there were other particles in the early universe, such as dark matter," Lang said.

　　 Scientists believe that these hypothetical particles may also exist today in the form of thermal residual particles. In this new study, the research team hypothesized that immediately after the Big Bang, the plasma undergoes a phase change that is similar to what happens when matter changes from one state to another, such as Water vapor bubbles formed in a boiling kettle, or water droplets formed when the steam is cooled.

　　 In this case, cooled plasma bubbles suddenly formed in the hot soup of the early universe. These bubbles expand and merge again, until the entire universe enters the next new stage.

"When these bubbles expand throughout the universe, they are like filters, filtering out dark matter from the plasma," Lang said. "In this way, the amount of dark matter we measure in the universe today is the Big Bang. A moment later, the direct result of this filtering process."

　　 These bubble walls will become a barrier. Only large-mass dark matter particles have enough energy to pass through the bubble barrier and enter the expanding bubble, thus avoiding the "Wild West". Other lighter particles are annihilated during this period. This can filter out low-quality dark matter particles and explain the large amount of dark matter observed today.

One of the most promising candidates for 　　 dark matter is massive weakly interacting particles (hermes outlet online). These hypothetical particles can reach 10 to 100 times the mass of protons, but they only interact with matter through two basic natural forces-gravity and weak nuclear force. They travel through the universe like ghosts, which can also explain the mysterious disappearance of dark matter that astronomers (such as Zwicky) first noticed nearly a century ago.

　　 In order to find WIMPs, physicists built huge advanced detectors underground. However, even though people have been searching for these mysterious particles for decades, we still found nothing. This has caused scientists in recent years to look for other dark matter particles that are lighter or heavier than WIMPs.

"One of the more anticipated aspects of our research ideas is that it applies to dark matter particles that are heavier than most other candidates (such as the famous WIMPs). In the past, most research has focused on finding WIMPs," The co-author of the study, Kopp, said, "Therefore, our research can promote the search for dark matter to expand to the field of heavier particles."

　　 This research can also provide opportunities for other future projects to find dark matter, such as the laser interferometer space antenna (LISA). LISA is a series of space probes spanning hundreds of miles to explore the ripples of gravitational waves in the universe.

　　 If the cosmic bubbles envisioned by Lang and his colleagues did exist in the early universe, they might leave detectable traces through gravitational waves. Part of the energy generated by the collision of two bubble walls may form gravitational waves that can be detected in future experiments.

　　 The research team also plans to expand their research scope to learn more about what happens when dark matter interacts with the bubble wall and when the bubble collides. "We know that dark matter is there, but we don't know anything else," Baker said. "If this is a new kind of particle, then we might have a good chance of detecting it in the laboratory. , We can determine its properties, such as mass and interaction, and further understand the universe."