Gravitational waves may have played an important role in the creation of dark matter in the early moments of the universe, according to a new study conducted by Professor Joachim Kopp of Johannes Gutenberg-University Mainz (JGU) and PRISMA++ Cluster of Excellence in collaboration with Dr. Azadeh Maleknejad of Swansea University. Published in physical review letterthe study introduces new calculations that point to a previously unexplored process by which so-called stochastic gravitational waves can give rise to dark matter.
This research addresses one of the biggest unanswered questions in particle physics. Everything we can see, including planets, stars, and life forms on Earth, is made up of visible matter, but this only makes up about 4 percent of the universe. Most of the universe remains invisible and is made up of dark matter and dark energy. Dark matter alone makes up about 23 percent of the universe.
Observations show that dark matter is widespread throughout the universe, forming galaxies and the largest cosmic structures. Despite its enormous impact, scientists still don’t know what dark matter is made of. Many theories and experiments are underway to uncover its true nature.
A new path to gravitational waves and particle formation
Gravitational waves are ripples in space-time produced by the most energetic events in the universe, such as collisions between black holes or neutron stars. However, not all gravitational waves originate from such dramatic events. Another type, known as stochastic gravitational waves, arises from various processes that do not involve massive objects.
These waves are much weaker and form part of the background signal that fills the universe. Many of them are very old, dating back to the early stages after the Big Bang. They could have been created at key moments in the history of the universe, such as during phase transitions or primordial magnetic fields as the universe cools.
“In this paper, we investigate the possibility that gravitational waves, which are thought to have been ubiquitous in the early universe, could be partially transformed into dark matter particles,” Kopp explained. “This leads to a new mechanism of dark matter production that has not been studied before.”
From waves in the early universe to dark matter particles
The study suggests that these early gravitational waves may have produced fermions that initially had little or no mass. Fermions are a wide variety of particles, including well-known examples such as electrons, protons, and neutrons. According to the researchers, these early fermions may have later gained mass and evolved into the dark matter particles that exist today.
What happens next with this theory?
“The next step in developing research in this area is to go beyond analytical estimates and perform numerical calculations to improve the accuracy of predictions. Another avenue for future research would be to investigate possible further effects of gravitational waves in the early universe. One example would be mechanisms that could explain the well-known difference between particles and antiparticles being produced,” Kopp said.
