Bubbles in our early universe may have resulted in the present abundance of dark matter, an elusive substance that pulls stars, but does not emit light, a study new shows.
Theory, described on October 9 in the journal Physical Evaluation Letters, possibly explaining exactly how dark matter condenses out of the fiery soup of the early universe. Since the astronomer Fritz Zwicky first proposed the existence of dark matter by 1933, tons of observational evidence has shown that something is lurking in the dark, invisible to our eyes and even the latest scientific tools. Dark matter leaves its fingerprints on the gravitational pull it exerts on the visible stars and galaxies observed by astronomers. The magnitude of that drag allows scientists to estimate what percentage of the universe is made up of dark matter; Current estimates suggest this dark matter makes up 80% of the mass of the universe.
Related: The 11 biggest unanswered questions about dark matter
Study co-author Andrew Long, associate professor of physics at Rice University in Houston, said: “Although we know how much dark matter our universe contains, over the decades, we still wondering about the nature and origin of dark matter. “Dark matter is a collection of Basic particles? If so, what are the properties of these particles, such as their masses and spins? What forces do these particles exert and what interactions do they experience? When is dark matter created and what interactions play an important role in its formation? “
Long and physicists Michael Baker, University of Melbourne in Australia, and Joachim Kopp, at Johannes Gutenberg University in Mainz, Germany, want to answer the last of these questions – when and when how? They looked at the first generation of the universe, a fraction of nanoseconds later Big Bang begins, a “Wild West” of particle creation and destruction, where particles collide and destroy each other rapidly as they form, Long said. At the time, the universe was a fiery soup pot of ultra-high-energy elementary particles, similar to the quark-gluon plasma that physicists created in today’s largest particle accelerator. This original soup was incredibly hot and thick, and too chaotic for more orderly subatomic particles like protons and neutrons to form.
But this space gun battle didn’t last long. After the universe began to expand, the plasma gradually cooled and the production of new particles halted. At the same time, the particles grew further apart and their collision rate drastically decreased until their numbers remained constant. The remaining particles are known as “thermal relics” by scientists, and become the matter we know and love today, such as atoms, stars, and finally humans. “In addition to all the elementary particles known today, there is reason to Imagine there were other particles present in the early universe, such as dark matter,” Long told Live Science.
Scientists believe these hypothetical particles may also exist today as thermal relics. In the new study, the team assumes that in the fraction of a second after the Big Bang, the plasma undergoes a phase transition similar to what happens today when matter moves from one state to another, For example, when steam bubbles form a pot of boiling water, or the steam cools to form water droplets.
In this case, bubbles of cold plasma suddenly formed in the boiling soup pot of the early universe. These bubbles expand and merge until the whole universe moves into a new stage.
“As these droplets spread across the universe, they act like filters of dark matter particles out of the plasma,” Long said. “In this way, the amount of dark matter we measure in today’s universe is the direct result of this filtration in the first seconds after the Big Bang.”
The walls of these bubbles will become barriers. Only the massive dark matter particles have enough energy to pass through the other side inside the expanding bubbles and out of the Wild West, destroying the lighter particles. This will filter out dark matter particles of lower mass and could explain the abundance of dark matter observed today.
The search continues
One of the leading candidates for dark matter is the weakly interacting mass particles, or WIMP. These hypothetical particles would be 10 to 100 times heavier than protons, but they would interact with matter only through two of nature’s fundamental forces: Gravitation and weak nuclear force. Passing like ghosts in the universe, they could be the cause of the disappearance of dark-matter astronomers, such as Zwicky, first noticed almost a century ago.
The search for WIMP prompted physicists to build giant modern detectors deep underground. But despite decades of searching for elusive particles, none have yet been found. This has led scientists in recent years to look for other dark matter particle candidates that are lighter or heavier than WIMP.
“An interesting aspect of the idea [of our research] is that it works against dark matter particles much heavier than most other candidates, such as the famous particle [WIMPs]Kopp, the paper’s co-author, said in an interview that most of the experimental searches in the past have focused on this. “Hence, our work spurs the expansion of dark matter searches for heavier masses.”
Their work could also open up the search for dark matter with other future projects such as the Space Antenna Interferometer Laser (LISA), a constellation of millions of miles of space probe designed to detect the ripples of gravitational waves through space.
If the cosmic bubbles that Long and his colleagues envision were present in the early universe, they could have left fingerprints detectable through gravitational waves, Long said. It is possible that some of the energy generated by the two walls of the colliding bubble will produce gravitational waves that future experiments might detect.
The team plans to expand their research to understand more about what happens when dark matter interacts with these bubble walls and what happens when the bubbles collide. “We know dark matter out there, but we don’t know a lot of other things,” Baker said. “If it’s a new particle, then chances are we could actually detect it in the lab. Then we could determine its properties, like its mass and its interactions. it, at the same time learning something new and deep about the universe. “
Originally published on Live Science.