A Can zero dimensional QFT be real?

[friend]

I've seen that we can create a toy model of QFT in zero dimensions. Everything occurs at a point. I wonder if this could possibly be real. It seems unlikely that we could ever prove that it is real because it would not propagate in our 3D world, so we could never observe it. Or maybe it can have effects that propagate in our "real" world. Any comments?

 

[Heinera]

Reference, please?

 

[PeterDonis]

I've seen that we can create a toy model of QFT in zero dimensions.

As @Heinera says, please give a specific reference.

 

[friend]

Reference, please?

Here's a reference to show that it is studied. Also, the 2nd chapter here. Although, I don't know what kind of interactions go on in zero dimensions. Maybe there are possible field strengths at that point that propagate forward and backward in time that interact with each other. I have no idea.

 

[Heinera]

It took me five minutes of reading to decide that this is a crackpot paper.

 

[friend]

It took me five minutes of reading to decide that this is a crackpot paper.

Well, of course, it does not represent reality as we know it. It supposed to be a toy model to develop techniques. But seriously, if the universe expanded from a point, then perhaps it is because a zero dimensional QFT somehow evolved into a 3D QFT. There seems to be some relation between lower and higher dimensional QFTs in the AdS/CFT correspondence.

 

[PeterDonis]

It took me five minutes of reading to decide that this is a crackpot paper.

It's not. But it doesn't mean what @friend appears to think it means.

if the universe expanded from a point

It didn't.

perhaps it is because a zero dimensional QFT somehow evolved into a 3D QFT

It couldn't.

There seems to be some relation between lower and higher dimensional QFTs in the AdS/CFT correspondence.

That relationship does not mean one QFT "evolves" into another.

 

[friend]

if the universe expanded from a point

It didn't.

You seem pretty confidence about that. Do you have any reference that proves that the universe did not expand from a point. It seem obvious to me. For if it did not come from a point, then you have to contend with a regions of space coming into being all at once. It seems easier to have one point come from nothing than a region. And doesn't GR point to a universe coming from a point/singularity?

 

[PeterDonis]

You seem pretty confidence about that.

Yes, that's because I'm familiar with what the cosmological models we use actually say. Your understanding of them appears to come from pop science treatments, which are often full of misstatements and misunderstandings.

Do you have any reference that proves that the universe did not expand from a point.

Check any recent cosmology textbook.

if it did not come from a point, then you have to contend with a regions of space coming into being all at once.

No, you don't. Spacetime is a 4-dimensional geometry; nothing has to "come into being".

doesn't GR point to a universe coming from a point?

No. Idealized GR models have an "initial singularity", but that does not mean the universe came from a point--the actual singularity itself is not part of spacetime in the model.

 

[PeterDonis]

@friend you labeled this thread as "A" level, indicating a graduate level understanding of the subject matter. You clearly do not have that given your latest post. I'm not going to relabel the thread since "A" is an accurate level for the subject matter. But I am closing the thread since your original question has been answered and your latest post is not relevant to the original question anyway. If you are thinking of opening a new thread about cosmology, I strongly urge you to take the time to learn what our current cosmological models actually say before doing so.

Thread closed.