Chaotic Inflation: Does it Involve Phase Transition?

[Ranku]

Does chaotic inflation involve phase transition, and if not, when does the phase transition of the breakdown of GUT symmetry occur?

 

[Chalnoth]

Does chaotic inflation involve phase transition, and if not, when does the phase transition of the breakdown of GUT symmetry occur?

Not directly, for sure.

As to when, I don't think that's entirely clear. It depends upon what the energy scale of inflation is. If the energy scale of inflation were above the GUT scale, then the symmetry breaking would happen after inflation ended. If the energy scale were below, then it would likely have to happen before inflation began. I think the current limits on the energy scale of inflation show that inflation was probably at a lower energy scale, indicating the GUT symmetry breaking happened first.

 

[Ranku]

As to when, I don't think that's entirely clear. It depends upon what the energy scale of inflation is. If the energy scale of inflation were above the GUT scale, then the symmetry breaking would happen after inflation ended. If the energy scale were below, then it would likely have to happen before inflation began. I think the current limits on the energy scale of inflation show that inflation was probably at a lower energy scale, indicating the GUT symmetry breaking happened first.

If GUT symmetry were to break before inflation began, would particle production start as soon as GUT symmetry is broken, or would it have to wait only after inflation ended?

 

[Chalnoth]

If GUT symmetry were to break before inflation began, would particle production start as soon as GUT symmetry is broken, or would it have to wait only after inflation ended?

The rapid accelerated expansion of inflation ensures that effectively no matter from before inflation began will be around any longer. The particles that we observe today were produced as inflation ended, via the process known as reheating.

So there may have been some particle production as a result of the GUT phase transition, but as long as that transition was before inflation (which seems likely), it doesn't matter.

 

[Ranku]

The particles that we observe today were produced as inflation ended, via the process known as reheating.

So is reheating therefore effectively the big bang?

 

[Chalnoth]

So is reheating therefore effectively the big bang?

The "big bang" isn't a real event. In the Big Bang theory, if you take the matter and radiation budget of the universe and extrapolate back in time, you find that this model predicts a singularity. But that singularity is fiction: the consequences of taking that singularity seriously result in nonsensical predictions. In terms of time, it would have been shortly before reheating, but there would have been no special event that would have actually happened at that time.

Because the "big bang" isn't a real event, when people use the word, they usually aren't talking about any specific event like reheating. They're just talking generically about the very early universe, and could mean anything from the event that started inflation, to reheating, to a span of time shortly after inflation that was still extremely hot, etc.. Precisely what the phrase means will vary somewhat from speaker to speaker.

 

[Ranku]

Thank you for your answers.