Gravitational waves could be responsible for the production of dark matter during the early phases of our universe’s formation, according to results of a new study by Professor Joachim Kopp from Johannes Gutenberg University Mainz (JGU) and the PRISMA ++ Cluster of Excellence in cooperation with Dr. Azadeh Maleknejad from Swansea University. Their work, published in Physical Review Letters , presents new calculations that explore a novel mechanism for the formation of dark matter through so-called stochastic gravitational waves.
In this way, they contribute to answering a fundamental question in particle physics. Planets, stars, and even life on Earth are all composed of visible matter. This type of matter only makes up about four percent of our universe. The vast majority is invisible, consisting of dark matter and dark energy. For instance, dark matter makes up about 23 percent of our universe. Astrophysical observations confirm that dark matter permeates the whole universe and forms galaxies as well as the largest known structures in the cosmos. However, the particles that make up dark matter are still unknown. Many theories and ongoing experiments are looking for an answer to this open question.
A new method for particle formation
Gravitational waves are a type of ripple in spacetime usually originating in some of the most intense and energetic processes in the universe, for example when two black holes or neutron stars merge. On the other hand, stochastic gravitational waves are caused by different phenomena without the participation of massive cosmological objects. Accordingly, their weaker signal forms part of the background noise of the numerous waves moving through our universe. However, they often are extremely old. Many of their originating phenomena occurred in the earliest stages of our universe's development, such as so-called phase transitions of matter, as the universe cooled down following the hot Big Bang, or primordial magnetic fields.
"In this article, we investigate the possibility of gravitational waves – which are believed to have been ubiquitous in the early universe – being partially converted into dark matter particles," Kopp explained. "This leads to a new mechanism of dark matter production that has not been researched before."
Kopp and Maleknejad show in their study that gravitational waves may well have led to the formation of mass-free or nearly mass-free fermions. The fermion family of particles includes electrons, protons, and neutrons, among others. These fermions from the early universe would then acquire mass and form the dark matter particles that still exist today.
"The next step in developing this line of research is to go beyond our analytical estimates and conduct numerical calculations to improve the accuracy of our predictions. Another avenue for future research is the investigation of further possible effects of gravitational waves in the early universe. One example for this would be a mechanism that could account for the well-known difference in particles and antiparticles produced," said Kopp.
Physical Review Letters
Gravitational-wave induced freeze-in of fermionic dark matter
31-Mar-2026