Extra dimensions -> power law lowering unification?

In summary, the existence of extra dimensions can lower the unification scale to the GeV scale, but this has unknown consequences for the LHC. It is experimentally verifiable.
  • #1
karnten07
213
0
Is it true that the existence of extra dimensions can lower the unification scale to the GeV scale? Does this mean that the LHC would be in range to detect a unification of couplings if this were true?
 
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  • #2
Well, I think you mean (?) TeV, not GeV. And this is highly dependent on the size of the extra dimensions.

So, for example, to have unification at the TeV scale, the extra dimensions have to have radius of an inverse TeV (multiply by hbar and c, and appropriate powers of 10 to get meters). If you believe that string theory is correct, then you also need 5 other dimensions that have Planck length radius, and you also have to explain this new hierarchy.

But, assuming you can explain WHY the dimension has a TeV radius (or, if you don't care), then there ARE definite consequences for the LHC, and it IS experimentally verifiable.
 
  • #3
BenTheMan said:
Well, I think you mean (?) TeV, not GeV. And this is highly dependent on the size of the extra dimensions.

So, for example, to have unification at the TeV scale, the extra dimensions have to have radius of an inverse TeV (multiply by hbar and c, and appropriate powers of 10 to get meters). If you believe that string theory is correct, then you also need 5 other dimensions that have Planck length radius, and you also have to explain this new hierarchy.

But, assuming you can explain WHY the dimension has a TeV radius (or, if you don't care), then there ARE definite consequences for the LHC, and it IS experimentally verifiable.

Are you saying: the bigger the dimension, the more we tend to notice it?
 
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  • #4
Yes. The larger the dimension, the more it effects the experiments that we'll preform at LHC. We can also hide the extra dimension partially or completely by making it small enough.
 
  • #5
does this assume that forces like gravity spread through these extra dimensions?
 
  • #6
BenTheMan said:
Yes. The larger the dimension, the more it effects the experiments that we'll preform at LHC. We can also hide the extra dimension partially or completely by making it small enough.

Thanks, Ben, though I don't quite follow--the circumference of these dimensions can be changed?

I'm a bit curious about gravity as well, but in another way. It seems that in the early universe where the spatial dimensions are at Planck scales, gravity would unify with the other forces, but only because the gravitons would have to be far massive to fit. Is this right?
 
  • #7
granpa said:
does this assume that forces like gravity spread through these extra dimensions?

Gravity is always spread through the other dimensions. This scenario assumes that the regular particles (electrons, quarks, etc.) can live in the extra dimensions.
 
  • #8
Phrak said:
Thanks, Ben, though I don't quite follow--the circumference of these dimensions can be changed?

This is a model building issue. You usually pick the circumference of the extra dimensions to solve some problem.

I'm a bit curious about gravity as well, but in another way. It seems that in the early universe where the spatial dimensions are at Planck scales, gravity would unify with the other forces, but only because the gravitons would have to be far massive to fit. Is this right?

I don't quite understand the question. What does "Far too massive to fit" mean?
 
  • #9
BenTheMan said:
This is a model building issue. You usually pick the circumference of the extra dimensions to solve some problem.

Thanks, though I had hoped you'd droped a bombshell: dimensions of variable size.

I don't quite understand the question. What does "Far too massive to fit" mean?

I should have said 'energetic'--higher frequency. If space were small, the limited number of wavelengths that would fit would be higher frequencies. Does that make sense?
 
  • #10
Phrak said:
Thanks, though I had hoped you'd droped a bombshell: dimensions of variable size.

Sorry :) I'm not sure how this would work. I've thought about it for about ten minutes, and couldn't convince myself that I had any kind of an answer.

I should have said 'energetic'--higher frequency. If space were small, the limited number of wavelengths that would fit would be higher frequencies. Does that make sense?

Yeah I understand now. Probably the answer is that the Plank length takes care of this. The radius of the compact directions is the Plank length, and the masses are quantized in units of the Planck Mass, which is 1/Planck Length. For a 2-d example, think about waves in a fishbowl, or something. If you set up a standing wave, there are exactly an integer number of waves in the fishbowl. You can think of the Planck mass resonances in terms of this---the lowest lying massive state corresponds to one wave in the fishbowl, etc.
 
  • #11
BenTheMan said:
Well, I think you mean (?) TeV, not GeV. And this is highly dependent on the size of the extra dimensions.

So, for example, to have unification at the TeV scale, the extra dimensions have to have radius of an inverse TeV (multiply by hbar and c, and appropriate powers of 10 to get meters). If you believe that string theory is correct, then you also need 5 other dimensions that have Planck length radius, and you also have to explain this new hierarchy.

But, assuming you can explain WHY the dimension has a TeV radius (or, if you don't care), then there ARE definite consequences for the LHC, and it IS experimentally verifiable.


Yes, i was just checking if it was at the GeV or TeV scale because this is really the issue i am confused about. The text says TeV which makes sense. But then for example in a paper by Dienes, Dudas and Gia Dvali where they discuss this accelerated power law, there is a graph showing the power law. But the scale is in GeV. Or does the TeV scale refer to unity which includes gravity by lowering the Planck scale?
 
  • #12
I don't know offhand. Can you post a link to the paper?

I'm familiar with Dienes, Dudas, and Gherghetta, but not Dienes, Dudas and Dvali.
 
  • #13
BenTheMan said:
I don't know offhand. Can you post a link to the paper?

I'm familiar with Dienes, Dudas, and Gherghetta, but not Dienes, Dudas and Dvali.

I'm sorry, i think that's who i meant. I think i get it now though, because unification is predicted to occur at 10^6 GeV which is 10^2 TeV? So with large extra dimensions unification occurs at the TeV scale. I think i was getting confused because the graphs were logarithmic. Thanks for the help though guys

Karnten07
 

1. What are extra dimensions and how do they relate to power law lowering unification?

Extra dimensions are hypothetical spatial dimensions beyond the three dimensions (length, width, and height) that we can observe. They are a common concept in some theories of physics, such as string theory. Power law lowering unification is a theory that suggests that the fundamental forces of nature (gravity, electromagnetism, and the strong and weak nuclear forces) can be unified at high energies. Extra dimensions play a role in this theory by providing a mathematical framework for unifying these forces.

2. How many extra dimensions are there?

The number of extra dimensions is not currently known or agreed upon. Some theories propose the existence of 10 or 11 dimensions, while others suggest there could be more than 11. The exact number of extra dimensions, if they exist, is an ongoing topic of research and debate among scientists.

3. Can we observe or measure extra dimensions?

No, we currently do not have the technology or capability to observe or measure extra dimensions. They are believed to be incredibly small and only have an effect at the subatomic level. However, some experiments, such as the Large Hadron Collider, are attempting to indirectly detect the presence of extra dimensions through their effects on particle interactions.

4. How do extra dimensions affect our understanding of the universe?

The existence of extra dimensions would greatly impact our understanding of the universe and the laws of physics. It would potentially explain the unification of the fundamental forces and could also provide explanations for other phenomena, such as dark matter and dark energy. However, until their existence is proven, their impact on our understanding remains theoretical.

5. Are there any practical applications of extra dimensions?

Currently, there are no practical applications of extra dimensions. However, their potential impact on our understanding of the universe and the laws of physics could lead to advancements in technology and energy sources in the future. Additionally, the research and study of extra dimensions may also have other unforeseen practical applications in fields such as mathematics and computer science.

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