The host of Ask a Spaceman and author of How to Die in Space is Paul M. Sutter.
A new model suggests that the graviton, the quantum mechanical force carrier of gravity, flooded the universe with dark matter before normal matter even had a chance to start.
The nature of dark matter and the history of cosmic inflation are two of the biggest puzzles in modern cosmology.
When the universe was very young, it experienced a period of rapid expansion known as inflation. The future evolution of the universe was dependent on this inflationary epoch, as it turned tiny quantum fluctuations of space-time into seeds that would eventually become stars.
Are axions our best bet in the hunt for dark matter?
The inflation event is not clear. For example, cosmologists don't know what triggered inflation, how long it lasted or when it shut off. The general picture is the only one that can explain the patterns in the microwave background and the distribution of matter in the universe. The statistics of those patterns match what we see in quantum fluctuations, which gives cosmologists the confidence they need to theorize that there is a link.
The universe was larger at the end of inflation. The contents of the universe had been flung far away from each other. Whatever powered inflation in the first place eventually ran out of steam. The driving force is called the inflaton by physicists and they think it was a quantum field that soaked all of space.
When inflation ended, the inflaton decayed, flooding the universe with particles. Inflation was a big part of the Big bang. If you imagine an empty universe filled with particles, then this is it.
All known particles were created when inflation ended. That same event made dark matter. There is a lot of evidence suggesting that dark matter is a new type of particle. Over 80% of the matter in the universe is accounted for by this particle.
Physicists have spent decades looking for any hint of a direct interaction between dark matter particles and normal matter. If dark matter is a particle, then it really doesn't like talking to normal matter. The story of inflation is annoyed by this non-detection of dark matter, because if the inflaton does not create dark matter along with normal matter in the early universe, there is no reason why it should.
A pair of physicists at the Helsinki Institute of Physics have proposed a new mechanism to generate lots of dark matter, even if the inflaton doesn't like to produce dark matter. The new mechanism relies on gravity.
This mechanism assumes that the inflaton and the dark matter don't talk to each other, so the dark matter particle isn't produced in the normal way at the end.
Why do we care about inflation?
The behavior of the inflaton was examined by the researchers. At the end of inflation, the inflaton is like a ball that just rolled down a steep hill, but hasn't settled down yet.
The preheating phase of the inflaton decay can give rise to some crazy physics. The inflaton may be able to connect to the dark matter particle if gravity is involved. The graviton is the quantum mechanical force carrier of gravity. Physicists found a way to make the graviton appear in the preheating phase near the end of inflation.
The pair discovered that when the graviton appears in the particle interactions, it could provide channels for the inflaton to decay into dark matter particles. The dark matter particles would be present in the universe before the rest of the normal matter.
This mechanism only works when space is doing something interesting. The dark matter particles faded when inflation finally messed with the universe's ability to create.
The physicists created the right amount of dark matter by tuning their model. It is still theoretical work. Physicists aren't sure how gravity interacts with particles. The current holy grail of modern physics is the regime of quantum gravity, a theory of strong gravity at small scales. The co-authors of the paper had to make a lot of assumptions about how gravity works at these scales.
The idea is interesting because it provides a way for the early universe to produce significant amounts of dark matter and for that dark matter to never talk to normal matter again.
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