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Reheating vs particle creation due to acceleration

  1. Jan 20, 2016 #1
    It seems during cosmic inflation the universe expands at an accelerated rate. This expansion is driven by the potential of the inflaton field. There's a slow role off of the inflaton potential as the universe inflates very rapidly and then the potential drops off rather sharply and the energy of the potential then goes into creating all the various kinds of particles common to the Standard Model.

    But this confuses me because I'm also told elsewhere (by the same person) that acceleration causes fluctuations in the quantum fields to produce particles. This occurs, for example, in the Unruh radiation. So my question is this: Does particle creation occur during the very fast inflationary expansion before the inflaton potential drops off? Or does particle creation only occur as the inflaton potential drop off sharply? It seems there should be particle creation at high inflaton potential too since there is very rapid acceleration. Thank you.
  2. jcsd
  3. Jan 20, 2016 #2
    I think you might be a bit confused, so I am going to stray a bit from the notion of "particle"

    By Heisenberg's Uncertainty Principle, quantum fluctuations create virtual particles that disappear soon after appearing. Occasionally, as we see in QCD, the energy necessary to produce these particles is not present, so the particle can never be measured (or else conservation of energy would be violated) A good example of this would be when a positron and an electron annihilate to form a Z boson, which decays into a muon and an anti-muon. A Z boson is very massive compared to the electron, so we never can measure it, but we know that it was "there" by the presence of the muon pair. But I digress

    These quantum fluctuations have been here since the beginning of the universe, but something very interesting occurred during inflation. Interactions between these fluctuations and the inflation field led these fluctuations to "use" energy from the inflation field, allowing the "particle" to actually exist, rather than being virtual. This is the idea behind the creation of particles in the inflation period.

    Now, I finally come to your question: does the particle formation occur IN the period, or after? The answer is that it occurs after, because the inflationary period created instability within the particles that we discussed before. This implies that maintaining the existence of these particles is quite challenging, and the rapidity of decay means that scientists generally consider most of the "particles" in the inflationary period virtual.

    Disclaimer: To physicists, I said a lot of technically imprecise statements that help explain the concept more effectively, but aren't exactly correct. However, I hope this gives you an answer and encourages you to learn more at : http://www.quantumdiaries.org/
  4. Jan 20, 2016 #3
    I could certainly see how during inflation, the particles created because of acceleration would immediately annihilate with their immediate neighbors since everything was so dense. This would make them all appear as if they were virtual since they were all annihilating with their neighbors just after creation. Is this the time when all the particles had not coupled to the Higgs mechanism yet so that no particles had mass at that time? Is this the era of the Grand Unified Field, where all the coupling constants were the same?
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