Experiments to check for extra dimensions

[billtodd]

Suppose we want to verify that there are curled-up dimensions.

What sort of experiments can you devise to check for them?
I mean what sort of experimental data are we looking for? (I guess it would be in high-speed particles' accelerators, but sure there are also cosmological observations that could potentially verify that they indeed exist).

And on another note, how small scales should we witness those features of extra curled dimensions?

 

[fresh_42]

The idea of curled-up dimensions is around 100 years old (cp. Kaluza-Klein theory). I don't think we know the answers to your questions given that we have searched for so long.

 

[Vanadium 50]

When you typed "limits on large extra dimensions" into Google, you got 286,000 results back. Which one didn't you understand?

 

[billtodd]

When you typed "limits on large extra dimensions" into Google, you got 286,000 results back. Which one didn't you understand?

I was reminded after reading Brian Green's popular book, that we are looking at scales of $10^{-33}m$ which is planck length. In the book it's written that in scales smaller than this QM will break. (At least there won't be any quantum fluctuations, i.e. Heisenberg Uncertainty Inequality should break down if there are scales smaller than planck length).

But my question, is what sort of experimental evidence should one look for extra curled-up spatial dimensions?

 

[billtodd]

I mean obviously, we can't see those curled-up extra dimensions directly. Then what should we get in the data that will give us indirect proof for those extra dimensions?

 

[phinds]

after reading Brian Green's popular book

There's part of your problem right there. Pop Science is not education. Particularly his books.

 

[billtodd]

There's part of your problem right there. Pop Science is not education. Particularly his books.

It's OK, I'll read Barton's book on String Theory after finishing reading a QCD book I am reading.
It's ok to sometimes breeze out of the technical stuff.
But I assume he doesn't lie in saying that String Theory says that's the limit of smallness.

 

[ohwilleke]

The Particle Data Group has a page that summarizes experimental efforts to look for extra dimensions. At the highest top level of that page is the following summary chart:

Review article 85 there explains this in prose (and helps to explain how limits expressed in eV units can be interpreted in the context of searches for extra dimensions).

There is basically no positive observational evidence of extra dimensions. The exclusions are moderately strict, down to curved extra dimensions at the scale of a millionth of a meter, and energy scales of multiple TeV for various phenomena that extra dimensions might make possible. But this is no where near the Planck scale, for example, and extra dimensions when we are largely confined to four of them, are inherently challenging to observe.

Somewhat related is the fact that the overall topography of the Universe as inferred from astronomy observations, is very nearly, although not perfectly, Euclidian (something that is called flat, even though in plain English flat means two dimensional rather than Euclidian).

 

[Vanadium 50]

But my question, is what sort of experimental evidence should one look for extra curled-up spatial dimensions?

And my question is, why do you expect us to Google this for you? You have told us that you are deserving of not just a PhD, but two PhDs. Why is using a search engine too much work for you?

As @fresh_42 points out, there is quite literally a century's work on this. You need to focus your question more if you expect other people to answer it. Otherwise this is like saying "Please summarize all of British history".

 

[ohwilleke]

And my question is, why do you expect us to Google this for you?

Physics Forum exists, generally, because our participants can sort the wheat from the chaff, and accurate statements of generally accepted physics from pseudo-science, out of the huge mess of stuff that appears on Google. Without expertise and education, distinguishing what is valid and what is not is not at all easy. We may also have "go to" resources for basic facts which other participants at PF may be unaware of until we point them out.

Even seemingly credible popularizations of science by real scientists can be misleading, and most people don't have the capacity to read the source material for themselves and evaluate it meaningfully.

 

[fresh_42]

Otherwise this is like saying "Please summarize all of British history".

If it can be carried, it is in the British Museum, if it can be occupied, it ends up as British restaurants.

 

[Vanadium 50]

Do you blame them? Pre-empire all they had was boiled beef and haggis.

 

[Mordred]

One also has to be careful that the term dimension often describes an indendent variable or other mathematical object. As well as some independent degree of freedom. for example spacetime the values of x, y,z and t are independent.
Not all dimensions necessarily have space components. (yet under graph one can oft use geometry to describe) You can have dimensions that are strictly mathematical.

 

[billtodd]

And my question is, why do you expect us to Google this for you? You have told us that you are deserving of not just a PhD, but two PhDs. Why is using a search engine too much work for you?

As @fresh_42 points out, there is quite literally a century's work on this. You need to focus your question more if you expect other people to answer it. Otherwise this is like saying "Please summarize all of British history".

I thought my questions were focused enough...
It seems PDG is the way for finding such stuff.

 

[billtodd]

The Particle Data Group has a page that summarizes experimental efforts to look for extra dimensions. At the highest top level of that page is the following summary chart:

View attachment 347520
Review article 85 there explains this in prose (and helps to explain how limits expressed in eV units can be interpreted in the context of searches for extra dimensions).

There is basically no positive observational evidence of extra dimensions. The exclusions are moderately strict, down to curved extra dimensions at the scale of a millionth of a meter, and energy scales of multiple TeV for various phenomena that extra dimensions might make possible. But this is no where near the Planck scale, for example, and extra dimensions when we are largely confined to four of them, are inherently challenging to observe.

Somewhat related is the fact that the overall topography of the Universe as inferred from astronomy observations, is very nearly, although not perfectly, Euclidian (something that is called flat, even though in plain English flat means two dimensional rather than Euclidian).

Well, I know from math that $\mathbb{R}^n$ equipped with an inner product is called Euclidean space.