Is it possible that strings are higher dimensional branes?

[Nav]

Are strings really just one dimensional? Is it possible that strings are 3 dimensional? Or even 10 dimensional?

 

[andrewkirk]

If they had more than one dimension, they would not be called strings.

There is something called 'brane theory' (brane is short for membrane) that has big membranes wobbling around in a many-dimensional manifold, with exciting things happening when they touch. In common language, a membrane is two-dimensional. So I imagine Branes have two dimensions, although it could be 'two or more'.

 

[Nav]

If they had more than one dimension, they would not be called strings.

There is something called 'brane theory' (brane is short for membrane) that has big membranes wobbling around in a many-dimensional manifold, with exciting things happening when they touch. In common language, a membrane is two-dimensional. So I imagine Branes have two dimensions, although it could be 'two or more'.

but what if they are like a string like a string on a guitar which has 3 dimensions

 

[JorisL]

Strings as is are really one dimensional. By definition. The same as point particles being zero dimensional (point particles $\neq$ atoms/nuclei although we often approximate those as points) by definition
In string theory there are several objects of higher dimensions. The ones you encounter quite soon in modern treatments are D-branes.
And a first idea about why they exist (that I've encountered so far) have to do with 'fixing' the endpoints of the string.

 

[phinds]

but what if they are like a string like a string on a guitar which has 3 dimensions

A "string" on a guitar is not a string in that sense, BECAUSE it is 3D. It is a tube with length, breath, and height, not a string

 

[Nav]

Is it possible that strings are higher dimensional branes but are just more compacted to seem like they are one dimensional when in reality they are more?

 

[cosmik debris]

Is it possible that strings are higher dimensional branes but are just more compacted to seem like they are one dimensional when in reality they are more?

It's the other way around, branes are like higher dimensional strings.

 

[rootone]

Or even 24 dimensional, that works too.
Have to remember that string theory is not as yet supported by evidence, though a lot of people like the idea.

 

[fzero]

Is it possible that strings are higher dimensional branes but are just more compacted to seem like they are one dimensional when in reality they are more?

There are models where higher-dimensional membranes can wrap a compact surface to give a string-like object in the noncompact dimensions. When the wrapped object is a so-called D-brane, these are sometimes called D-strings to distinguish them from the fundamental string. Also, in one version of M-theory, starting from 11D spacetime, a membrane (two-dimensional object) is wrapped on a circle to form the fundamental string of the so-called IIA string theory in 10D spacetime. There is some discussion at a very basic level at http://superstringtheory.com/basics/basic7.html

 

[cosmik debris]

Or even 24 dimensional, that works too.
Have to remember that string theory is not as yet supported by evidence, though a lot of people like the idea.

I think you may be thinking of 26-D bosonic string theory, it is not the strings that are 26-D that is the space they live in.

 

[haushofer]

You end up with branes, and as far as I know the action of such a brane is not renormalizable, and we don't know how to write a Polyakov-like action like we know for strings. I'm also not sure how you could quantize such an action.

 

[samalkhaiat]

You end up with branes, and as far as I know the action of such a brane is not renormalizable, and we don't know how to write a Polyakov-like action like we know for strings. I'm also not sure how you could quantize such an action.

The Polyakov action of a p-brane (in D-dimensional spacetime) is just the (p+1)-dimensional Sigma model: $$S[X] \sim \int d^{p+1} \sigma \ \sqrt{-\gamma} \ \gamma^{ij}(\sigma) \ \partial_{i}X^{\mu}(\sigma) \ \partial_{j}X^{\nu}(\sigma) \ g_{\mu \nu}(X) ,$$ where $\sigma = (\sigma^{0} , \sigma^{1} , \cdots , \sigma^{p})$ are the world-volume coordinates and $X^{\mu}, \ \mu = 0, 1, \cdots , D-1$ are the spacetime coordinates of the brane: mapping of the (p+1)-dimensional parameter space of the p-brane into spacetime.
Notice that for $p = 0$, the above action becomes that of a point particle, i.e. 0-brane is point particle. For $p=1$, you get the Polyakov action for string, i.e. 1-brane is string, and 2-brane is a membrane, etc.
When a p-dimensional object moves in spacetime, it sweeps out a (p+1)-dimensional tube. This fact can be used to write a Polyakov-type action for any value of p.

Sam

 

[Darryl]

I think if lower dimensional object can exist in higher dimensional space, then yes there is no reason (to me) that something can exists and have length but no height or width. Which any number of 1d objects and exist in a 2d space. So is a brane a 2d object composed of 1d strings? Our Universe is a 3d object in 4d space? Could those universes be separated by the 4th dimension?