Is it possible that dark matter is a cosmic relic from another dimension? According to researchers, gravity propagates through extra dimensions and manifests as massive gravitons in our universe.
An elusive substance that exists in our universe called “dark matter” has just gotten even more mysterious and interesting. Researchers have suggested that dark matter might be a cosmic relic from extra dimensions.
According to a paper published in Physical Review Letters, researchers found that if there are extra dimensions, we should be able to spot tell-tale signs of them within our universe. Dark matter, as it turns out, can help us do that.
Scientists believe dark matter is made of massive particles called gravitons that entered existence in the first instant after the Big Bang. Dark matter accounts for the vast majority of mass in the universe. New research suggests that the hypothetical particles–gravitons–may come from extra dimensions.
But how do we know that? Researchers calculated that just the right amount of these particles could have been created to account for dark matter, which is only visible via its gravitational pull on ordinary matter.
“Massive gravitons are produced by collisions of ordinary particles in the early universe. This process was believed to be too rare for the massive gravitons to be dark matter candidates,” revealed co-author Giacomo Cacciapaglia, a physicist at the University of Lyon in France, in an interview for Live Science.
In a study published in February of 2021 in Physical Review Letters, Cacciapaglia and Korea University physicists Haiying Cai and Seung J. Lee realized that the early universe had created enough gravitons to account for all the dark matter observed today.
Gravitons–the tell-tale sign
It was found that gravitons would likely be smaller than 1 megaelectronvolt (MeV), so no larger than twice the mass of an electron.
There is a big difference between this mass level and the scale at which the Higgs boson produces mass for the ordinary matter – which is crucial for the model to account for all the dark matter contained within the universe. To put this into context, a proton weighs roughly 940 MeV compared to the neutrino, the lightest known particle that roughly weighs 940 MeV.
Scientists, however, were not looking for gravitons. They were looking for evidence of other dimensions and discovered gravitons. Experts believe that several other dimensions exist in addition to the three dimensions of space, and time, the fourth dimension.
According to the team’s theory, gravity propagates through extra dimensions and manifests as massive gravitons in our universe.
However, there is a scratch; these particles–gravitons–would only interact weakly with ordinary matter, and only through the force of gravity. In some ways, this describes dark matter, which does not interact with light but can exert a gravitational influence across the entire universe. Galaxies, for example, are held together by the gravitational influence.
“The main advantage of massive gravitons as dark matter particles is that they only interact gravitationally, hence they can escape attempts to detect their presence,” Cacciapaglia revealed.
Contrary to this, other very subtle concepts, such as weakly interacting massive particles, axions, and neutrinos may also bring about the vague experience of dark matter. This is because they interact with other ordinary forces and fields.
A further advantage of gravitons is that they have almost no interaction with other particles and forces in the universe via gravity.
Because gravitons are created in extremely rare circumstances, physicists did not consider gravitons to be candidates for dark matter. Gravitons would be created at a much slower rate compared to other particles.
Researchers found, however, that gravitons would have been produced much more quickly than previous theories suggested in the picosecond (trillionth of a second) after the Big Bang. Researchers found that massive gravitons could fully explain the amount of dark matter we detect in the universe with this enhancement.
“Due to their very weak interactions, they decay so slowly that they remain stable over the lifetime of the universe,” Cacciapaglia explained to Live Science.
“For the same reason, they are slowly produced during the expansion of the universe and accumulate there until today,” he added.
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