A new model of the very early universe suggests that the graviton, the carrier of the quantum mechanical force of gravity, flooded the universe with dark matter before ordinary matter had a chance to begin.
The proposal could be a way to connect two of the biggest outstanding mysteries of modern cosmology: the nature
dark matter The history of cosmic inflation.
Many cosmologists believe that when
Universe Incredibly young (less than a fraction of a second old), it experienced a period of incredibly rapid expansion known as inflation. This inflationary epoch was crucial to the future development of the universe, as this astonishing expansion turned the microscopic quantum fluctuations of space-time into the seeds that would one day become starsAnd galaxies And Clusters of groups.
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The actual inflation event is somewhat ambiguous. For example, cosmologists don’t know what caused inflation, what drove it, how long it lasted or when it stopped.) But only this general picture can explain the patterns in
cosmic microwave background (The later light pattern formed when the universe was 380,000 years old) and the widespread distribution of matter in the universe. The statistics of these patterns match what we see in quantum fluctuations, giving cosmologists the confidence they need to posit a link.
At the end of inflation, the universe was much larger than it was before. But it was also much more empty, as all the content that was in the universe previously had been tossed away from each other. There was only one thing left: Whatever inflation was supported in the first place but eventually ran out of steam. Cosmologists call this driving force “
InflationAnd they think it was a quantum field that engulfed all of space.
When inflation ended, inflation died down, inundating the universe with the variety of particles we see today. In many ways, inflation was the “real”
the great explosion. If you imagine an empty universe suddenly rich in an explosion of particles, this is it.
Silent dark matter
When inflation ended, it led to the formation of all known particles. So, it is assumed that this same event also produced dark matter. Cosmologists aren’t sure what dark matter consists of, but there is an abundance of evidence to suggest that it is a new, unknown type of particle. Whatever this particle is, it accounts for more than 80% of all matter in the universe.
Physicists have spent decades searching for any hints of a direct interaction between dark matter particles and ordinary matter, to no avail. If dark matter is really a particle, then it really doesn’t like talking to normal matter. This lack of dark matter detection is very upsetting to the inflation story, because if dark matter didn’t talk to normal matter, there was no good reason why dark matter was created alongside normal matter in the early universe.
Now, a couple of physicists at the Helsinki Institute of Physics have proposed a new mechanism for generating so much dark matter in the early universe, even if the Inflatons didn’t want to produce dark matter. This new mechanism relies solely on
This mechanism, which physicists explained in a research paper in the preprint database
arXivassumes that inflation and dark matter do not talk to each other, so a dark matter particle is not produced in the normal way at the end of inflation.
Related: How did inflation happen and why do we care?
Instead, the researchers examined the behavior of inflation just before it decayed. At the end of inflation, right before the bulge disappears and gives rise to the particle garden in our universe, the flow cascades around the universe like a ball that has just rolled up a steep hill but has not yet settled.
Cosmologists call this step the preheating phase of bulge dissolution, and it can lead to some crazy physics. For example, in this short phase, gravity itself may play a major role, allowing the inflaton to contact a dark matter particle. In this case, gravity takes the form of the putative quantum mechanical force carrier, the graviton. Normally, gravitons are not involved in particle interactions, but physicists have found a way to appear in a preheating phase near the end of inflation.
The pair discovered that when graviton appears in particle interactions of this era, it can provide channels for influenza to decay into dark matter particles. Then these dark matter particles are already present in the universe before the rest of the ordinary matter follows suit when the blowing eventually disappears.
This mechanism only works when the space is doing something interesting, such as rapidly expanding during inflation. And so, when inflation finally tampered with the universe’s ability to form, the dark matter particles vanished.
Physicists have fine-tuned their model to create the right amount of dark matter required by observations of the universe. However, it is still a theoretical work. Importantly, physicists aren’t quite sure how gravity interacts with particles. This is the system
quantum gravity, the theory of strong gravity on the small scales, the current holy grail of modern physics. Therefore, for their work, the paper’s co-authors had to make a lot of assumptions about how gravity works at these scales.
However, the idea is interesting because it provides a way for the early universe to produce large amounts of dark matter and for this (essentially) dark matter to never talk to normal matter again.