A very elusive and strange matter – dark matter makes up most of the mass of the universe, and it may include gravitational particles that first appeared after the Big Bang. And Gravitons are proposed elementary particles based on the framework of quantum field theory whose quantum exchange can induce gravity. A new theory suggests that these hypothetical particles could be cosmic relic from extra dimensions.
The researchers’ calculations suggest that there may be just enough of these particles in the current universe to explain dark matter. Currently, physicists have not actually observed the existence of dark matter, and can only “observe” it through its gravitational effect on ordinary matter. Previously, this process was thought to be highly unlikely, so a large number of gravitational particles could not be dark matter candidates.
In a new study published in the February issue of Physical Review Letters, physicists found that the early universe may have produced a large number of gravitational particles, enough to explain matter. Dark is currently detected in the universe.
The study found that if gravitons in the early universe existed, their mass would be less than 1MeV and no more than twice the mass of an electron. This mass level is much lower than the scale at which the Higgs boson gives rise to the mass of normal matter – key to the model that produces enough Higgs bosons to explain all of the dark matter in the universe. (For comparison, the lightest known particle, a neutrino, has a mass of less than 2 eV, while a proton has a mass of about 940 MeV, according to the US National Institute of Standards and Technology.)
The team discovered these hypothetical gravity while searching for evidence of extra dimensions. Some physicists suspect that there are additional dimensions beyond the three-dimensional space and fourth-dimensional time that we have observed. According to the team’s theory, as gravity moves through additional dimensions, it will pop up in our universe as massive gravitational particles.
However, these particles can only interact weakly with ordinary matter, and only through gravity. This description is very similar to what is currently known about the properties of dark matter: dark matter does not interact with light, but has a gravitational effect that can be felt anywhere in the universe. For example, physicists believe that the gravitational effect of dark matter is what prevents galaxies from splitting.
In general relativity, gravity is seen as a geometric phenomenon, the curvature of space-time. In current physics, this idea has achieved great success. On the other hand, the view of quantum mechanics holds that force is produced by the exchange of discrete (i.e. quantum) energy packets. Different quanta produce different forces. Based on this view, the Standard Model of Quantum Physics believes that fundamental interactions are produced by quantum exchanges and proposes the theory of the measurement boson, such as the electromagnetic force produced by photon exchange, and the weak nuclear force produced by W and Glass Z Dons exchange is produced, as well as the strong nuclear force produced by the exchange of gluons. Theory predicts that gravity should also be generated by the exchange of some kind of boson, known as graviton.
The main advantage of the hypothesis of large numbers of gravitational particles as dark matter particles is that these particles interact only through gravity and thus avoid attempts to detect their existence, as opposed to Other dark matter candidates – such as extremely weakly interacting particles (WIMPs), axions and neutrinos – can also be detected through their very subtle interactions with other forces and fields. Many scientists believe that WIMP is the most promising candidate for dark matter, but the latest research suggests that dark matter should be smaller than WIMP. There are currently a number of experiments looking for WIMPs that theoretically must be performed underground to avoid interference with cosmic rays.
The fact that a large number of gravitational particles barely interact with other particles and forces in the universe through gravity offers another advantage. Because their interaction is so weak, they decay so slowly that they remain stable throughout the lifetime of the universe, for the same reason they are created slowly during the expansion of the universe, accumulating condensate continuously to this day.
Physicists previously thought that gravitational particles were unlikely to be a candidate for dark matter because the process that produced them was extremely rare. So graviton is produced at a much lower rate than other particles. But the team found that within a trillionth of a second after the Big Bang, there could be much more gravity than previously thought. This increase in numbers is enough to allow gravitons to fully explain the amount of dark matter we have detected in the universe, the study suggests.
Since a large number of gravitational particles are formed below the energy scale of the Higgs boson, they do not suffer from the uncertainty associated with higher energy scales, which particle physics cannot currently describe accurately. The team’s theory links physics studied at particle accelerators such as the Large Hadron Collider (LHC) with the physics of gravity. This means that very large particle accelerators like CERN’s Future Circular Collider (FCC) can be used to look for evidence of these potential dark matter particles. The FCC will be four times the size of the LHC, the world’s most powerful particle accelerator, and will have an impact energy six times that of the LHC. It is planned that the accelerator will start operating in 2035.
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