What is the Energy of the Big Bang?

[Chalnoth]

Is this equivalent to energy instability or runaway like a cigarette turning into a huge forest fire or like the beating of a butterflies wings eventually turning into a hurricane?

Well, that's a very different sort of situation. Those things happen because some highly complex, non-linear systems can have changes which are out of proportion to the inputs that caused said changes. These sorts of changes have the property that they are very hard to predict, for instance, precisely because the eventual state of two systems with only very slightly different inputs can be so dramatically different.

Inflation is a bit of a different beast, because even though you're causing a massive ballooning of the universe, it's a highly deterministic one. You can make small changes to the starting configuration, and it really doesn't make much of any difference as to how inflation progresses (provided the changes you make don't stop inflation from occurring altogether). In fact, if you're willing to believe the no hair theorems as they apply to inflation, the initial conditions can't have anything whatsoever to do with the eventual state of the universe: all that is important is that inflation begins and lasts long enough to produce a large universe.

 

[Tanelorn]

Thanks Chalnoth, do we know what happened to stop inflation when it did? Assuming it did actually stop!

 

[Chalnoth]

Thanks Chalnoth, do we know what happened to stop inflation when it did? Assuming it did actually stop!

The simplest models of inflation have inflation being driven by a field that has some potential energy, but is away from the minimum of the potential. As inflation progresses, the field slowly progresses towards the minimum of the potential. This progression is slowed by the extremely rapid expansion, which is what allows the universe to inflate in the first place. Once the field hits the minimum, however, it oscillates about that minimum, which causes the field to decay into standard model particles. This process is known as "reheating".

Once that has occurred, the universe is dominated by radiation energy density, and the expansion slows down dramatically. What follows is basically standard big bang theory.

 

[bcrowell]

It's not quite that simple in GR, though, because GR doesn't necessarily deal solely with point-like objects. When you have things like fluids or other extended objects, you can't reduce the conservation of the stress-energy tensor to conservation of energy-momentum in the usual sense.

I think you're trying to describe the difference between global and local conservation of energy-momentum in GR, but this formulation doesn't work. The local conservation of energy-momentum described by the zero-divergence property of the stress-energy tensor has nothing to do with whether the stress-energy tensor describes a fluid or a collection of pointlike objects. It is exact in either case.

But in any event, that's somewhat of an aside. The point is that if you consider, say, an expanding universe full of radiation, the energy of a comoving volume decreases over time. Most people would consider this to be a situation where energy isn't conserved. Similarly, with inflation, you can take a region of the universe much smaller than a proton that has rather high energy density but very small size, and within a fraction of a second expand that region to be many light years across, with an energy density that has changed very little. Most would also call that a situation where energy isn't conserved, and this is pretty critical to the topic at hand because it allows huge amounts of matter to come from very little.

Yes, that's an example of the kinds of problems you get with defining *global* energy conservation in GR. It has nothing to do with the type of *local* energy conservation described by the zero-divergence property of the stress-energy tensor.

Have you looked at the section in MTW that I pointed you to? Do you have a copy of the book? If not, I might be able to find a reference that would be more accessible to you. This is really just standard stuff about the interpretation of mass-energy in GR.

 

[Chalnoth]

I think you're trying to describe the difference between global and local conservation of energy-momentum in GR, but this formulation doesn't work. The local conservation of energy-momentum described by the zero-divergence property of the stress-energy tensor has nothing to do with whether the stress-energy tensor describes a fluid or a collection of pointlike objects. It is exact in either case.

My point is that I don't think you can make the equivalence of the connection between the conservation of the stress energy tensor to the conservation of energy-momentum for an object that cannot simply be described using its energy-momentum. For point-like objects, sure, that equivalence makes sense. But GR doesn't deal with solely point-like objects.

Yes, that's an example of the kinds of problems you get with defining *global* energy conservation in GR. It has nothing to do with the type of *local* energy conservation described by the zero-divergence property of the stress-energy tensor.

Have you looked at the section in MTW that I pointed you to? Do you have a copy of the book? If not, I might be able to find a reference that would be more accessible to you. This is really just standard stuff about the interpretation of mass-energy in GR.

No, I don't have a copy. We used a different text in our classes, but I left nearly all my textbooks back at home when I came here to Italy anyway.

 

[Karolingfield]

A brazilian physicist seems to be solved the cosmological problem. In a paper published by the american journal of Physics Progress in Physics [Assis, Armando V.D.B. On the Cold Big Bang Cosmology. Progress in Physics, 2011, v. 2, 58-63]:

http://www.ptep-online.com/index_files/2011/PP-25-14.PDF

, the author seems to solve the Einstein field equations with one extra postulate in which he argues that the Dark erergy arises from an illusion due to a persistent Heisenberg uncertainty claiming that the energy content os the universe is totally due to Heisenberg fluctuation. With this, he obtains the correct value of the black body background temperature of 2.7 Kelvins as well the fitting of the cosmological data.

Also, the author seems to go via an alternative route in which the conservetion of energy is weakened by a lack of application of the Noether's theorem (in author's words). Since the subject is important and connected to the entropy problem and to the energy problem, I think this claimed results shoul have some further discussion within the forum.

Karolingfield.

 

[AstrophysicsX]

We think that there was more matter than antimatter based on the fact that there isn't a lot of antimatter around us. I have read that antimatter looks just like regular matter, so how would we distinguish it from light years away. Our neighboring galaxies could be made of antimatter and since it looks regular we couldn't distinguish it.

 

[Misericorde]

We think that there was more matter than antimatter based on the fact that there isn't a lot of antimatter around us. I have read that antimatter looks just like regular matter, so how would we distinguish it from light years away. Our neighboring galaxies could be made of antimatter and since it looks regular we couldn't distinguish it.

On the margins where matter and antimatter meet it would annihilate. The intense gamma rays and other radiation would be recognizable, but has not been observed. It's possible that beyond our cosmological event horizon there are antimatter regions, but there's no evidence for that idea.

Even if you say a huge region of space is filled with antimatter only, it has to meet its opposite at some point, and it will annihilate. If our neighboring galaxies were anti-matter, they'd be releasing a ton of energy just as they move through the non-antimatter interstellar medium. If that medium itself were antimatter, than our galaxy would be annihilating with it. Either way, this would have been observed, and it hasn't been.

 

[phinds]

Chronos, do we not also need some kind of cause and effect, especially for something as sudden and energetic as the big bang?

Perhaps because I have not yet read enough about quantum mechanics and cosmology to have it totally crushed, I still maintain a belief in cause and effect. The fact that we have not a clue as to cause and effect at the singularity does not, to me, say that there ISN'T one.