Force unification in Big Bang

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I have been reading that until the universe was one Planck time old (10-43 seconds) all the forces were unified into one. Do we know why would they be unified? Is it very large temperatures and pressures? Could we replicate it in the labs one day? Today Electric and Magnetic force are unified into Electromagnetic force. Could they separate one day?
 

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Simon Bridge
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I have been reading [where?] that until the universe was one Planck time old (10-43 seconds) all the forces were unified into one. Do we know why would they be unified?
No. We reason that, by current understanding, they must have been (for some ideas about physics to hold) ... due to the scale of the Universe at the time. You maybe want to treat it as an assumption to be tested.

Could we replicate it in the labs one day?
Nobody knows.
By current models - almost certainly not. This would involve compressing space-time itself.

Today Electric and Magnetic force are unified into Electromagnetic force. Could they separate one day?
The unification, in this case, was a mathematical unification ... a realization that what we had been calling two separate forces were, in fact, due to an underlying process looked at from different perspectives. This is to say: it's a correction of an historical misunderstanding: a mistake ... it is not clear how any existing force could separate into some collection of other forces as yet unknown but there is no reason to suspect that electromagnetism, should it split into other forces, would split into electricity and magnetism.

http://www.democraticunderground.com/discuss/duboard.php?az=view_all&address=228x42016
 
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  • #3
I read it on the wikipedia article on Big Bang. I know, wikipedia is not very accurate, this is probably one of the mistakes.
 
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Simon Bridge
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I think there is a tendency for sources to be a little glib when talking about big-bang cosmology. Wikipedia is echoing that.

You got to realise there are a lot of suppositions going on, and each model has a slightly different set.
The "accepted" one is the one that best passes Occam's razor ... in this instance, it is the one where the forces unify when the density is high enough.
It's one of the things you go into when you do a foundational cosmology course at post-grad college level. I'm having a real hard time finding someplace with a definitive statement about it. I've made a note to do something about that next time I have to teach this ;) so this is one of those cases where someone asking a "simple" question affects things at this end.
 
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haushofer
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I have been reading that until the universe was one Planck time old (10-43 seconds) all the forces were unified into one. Do we know why would they be unified? Is it very large temperatures and pressures? Could we replicate it in the labs one day? Today Electric and Magnetic force are unified into Electromagnetic force. Could they separate one day?
Well, one hint is given by the standard model. Interaction strengths depend on the energy scale of the process. One can show that for a certain energy scale, all three interaction strengths become almost equal. Because the corresponding energy scale is very high, and we suspect that the standard model needs extension for such high energy scales, many physicists suspect that this 'almost' is not a coincidence and becomes an 'exactly' once the standard model has been extended in the right way.

I think the inclusion of gravity in this unification is a bit more speculative, since we don't have a theory of quantum gravity yet. But I could be wrong here.
 
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Well, one hint is given by the standard model. Interaction strengths depend on the energy scale of the process. One can show that for a certain energy scale, all three interaction strengths become almost equal.
Would that mean that some forces are unified near the black holes?
 
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haushofer
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No. Being near black holes doesn't imply high-energetic processes. Actually, a local observer near the horizon doesn't experience anything spectaculair.

That is to say, when you look at it from a classical point of view. Nowadays so-called 'firewalls' are being proposed, and that would change the situation.
 
  • #8
So what is then high energy process?
 
  • #9
haushofer
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A process which involves an energy (e.g. center of mass-energy) comparable to the GUT scale, in this case.
 

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