Inflation "cooled Universe from 10^27 to 10^22 kelvins" why?

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Discussion Overview

The discussion centers on the temperature estimates during the inflationary phase of the universe, specifically the transition from approximately 10^27 to 10^22 kelvins. Participants explore the basis for these estimates and the implications of inflationary theories on temperature and density during this period.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested

Main Points Raised

  • One participant questions the basis for the temperature estimates of 10^27 and 10^22 K, suggesting that if inflation lasted only a few seconds, the density would drop to zero, leading to a temperature of zero.
  • Another participant requests a source for the temperature statement, indicating a need for verification.
  • A third participant identifies a potential source for the temperature estimate, linking it to a paper by Guth on phase transitions in the early universe.
  • One participant proposes that the 10^22 K temperature refers to the state after reheating, following the completion of the super-cooled phase transition, though they express uncertainty about this interpretation.

Areas of Agreement / Disagreement

Participants express differing views on the implications of inflation for temperature and density, with no consensus reached on the validity of the temperature estimates or the sequence of events during inflation.

Contextual Notes

Participants highlight the uncertainty surrounding the duration of the inflationary phase and the assumptions involved in estimating temperatures, as well as the dependence on specific theoretical frameworks.

nikkkom
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I've seen numerous descriptions of inflationary phase a-la "The universe was supercooled from about 10^27 down to 10^22 kelvins".

However, I do not understand what is the basis for such estimation. We do not even know with any certainty how long the inflationary phase lasted. For one, "eternal inflation" theories even say that it may be lasting something like billions of years.

If it lasted even "only" a few seconds, the inflationary vacuum expansion surely diluted all preexisting particles to zero density. Thus, temp in this case should not be 10^27 or 10^22 K. It should be zero.

Then decay of the false vacuum does create a new hot and dense state. _Now_ it can be at ~10^22 K (if you know a paper where it is estimated to be about this temp to match observations, please post a link).

So, to me, the sequence of events in inflation theories should be:
[whatever] -> temp and density rapidly falls, possibly even to zero -> decay of vacuum, reheating to high temp (10^22K?) -> "normal Big Bang" scenario.
 
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Please give an appropriate source for this statement.
 
I believe the final temperature in the Guth statement refers to the inflationary patch post-reheating. After the super-cooled phase transition completes, the latent heat is released, reheating the system. Not certain about this, though.

This reference might be helpful: https://journals.aps.org/prl/pdf/10.1103/PhysRevLett.44.631
 

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