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The phase transition of the universe during inflation

  1. May 10, 2012 #1
    This is from Krauss' A Universe from Nothing:

    It seems like he's saying that before inflation kicked in around 10^-36 or 10^-34 I forget which that the universe, I'm guessing from 10^-43 - 10^-36 was in some sort of false vacuum state, analogous to the way matter changes phase from gas to liquid. Is that right?
  2. jcsd
  3. May 10, 2012 #2
    It's not that the universe itself was in this state - the field that drives inflation, the inflaton field, was in a false vacuum. Essentially, this field would have been trapped in a high density false vacuum, which would have produced an enormous negative pressure. In general relativity, negative pressures can drive the metric expansion of space.

    Guth's original model of inflation held that, after the universe inflated exponentially for a short period of time, regions of the inflaton field would decay, through a process called quantum tunneling, into true vacuum 'bubbles'. These bubbles would collide, putting the whole universe in a true vacuum state, ending inflation. Guth actually realized that under his model of inflation, it tended to last forever, as the bubbles never were able to reach each other. He called this 'eternal inflation', which holds that the true vacuum bubbles never collide, and give rise to an inflationary multiverse.

    However, Guth's 'old inflation' was replaced by new inflation, called slow-roll inflation. In this model, the inflaton field slowly rolls down a potential energy 'hill', until the inflaton field reaches a true vacuum, and decays into a hot bath of radiation.
  4. May 10, 2012 #3
    Does anyone know what a false vacuum is like? For some reason or other I get the feeling that the false vacuum is E and a true vacuum is mc2

    what type of matter is in the bubbles?

    Then when the radiation cools to maybe 8000 k matter begins to form, right?
  5. May 10, 2012 #4
    A false vacuum is just a local minimum - rather than a true vacuum, which is the global minimum. False vacuums are unstable, as fields will, via instanton processes (e.g. quantum tunneling) tend to decay into a true vacuum, a desirable, low energy state.
    They aren't literally bubbles (that's why I used quotations), they are regions in a true vacuum that are expanding at a normal rate, and not inflating. They're filled with a decayed inflaton field, which translations to a bath of radiation.
    I'm not sure of the exact temperature, but that is the idea, yes. Once the radiation cooled, particle pair production created matter and anti matter. Somehow, matter managed to outnumber anti-matter by one part in a billion. After ~70,000 years, matter began to dominate radiation.
  6. May 10, 2012 #5


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    The temperature would have been in the 10 trillion K range (~ a microsecond age) when it was cool enough for protons and neutrons to exist.
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