What is the Tension of Brane?

[Abolhassan]

Hi
I am working on brane-world cosmology. I have two questions:
1-What is the tension of brane?
2-In this model we say that our universe and all kind of energy is confined on 4-dimensional surfaces and only gravity can propagate along the fifth dimension (bulk). In some papers we can see they introduce a lot of kind matter for brane. Are they confined on another 4-dimensional surfaces or not?

 

[Chalnoth]

Hi
I am working on brane-world cosmology. I have two questions:
1-What is the tension of brane?
2-In this model we say that our universe and all kind of energy is confined on 4-dimensional surfaces and only gravity can propagate along the fifth dimension (bulk). In some papers we can see they introduce a lot of kind matter for brane. Are they confined on another 4-dimensional surfaces or not?

I'm not sure what you're asking for point one. If you mean conceptually, well, then the tension on the brane is exactly the same as any other tension you might think of, such as on a rope. It's just a measure of how much the brane is stretched.

As for the matter being confined to the brane, what happens there is that you end up with open strings which have endpoints confined to the brane. These endpoints are identified with massless particles, and since it is expected that all particles in the standard model are massless, and the standard model symmetries are a subset of the string theory symmetries, it is expected that all of the standard model particles (plus some more) can be explained as being the endpoints of these strings.

Gravitons, however, tend to "detach" from the brane, so you can't confine them in the same way you confine standard model particles.

 

[Naty1]

You'd probably find THE ENDLESS UNIVERSE from Paul Steinhardt and Neil Turok about cyclic brane cosmology worthwhile.

They discuss the relationships between brane kinetic energy, gravity, dark energy and brane movement and collisions...I don't recall brane tension playing any central role in their model...

A not very insightful summary appears in wikipedia: http://en.wikipedia.org/wiki/Ekpyrotic_universe

You might also find this discussion helpful...note D branes are the type in which you are likely interested...
http://en.wikipedia.org/wiki/String_theory#Brane-world_scenario

Also the BRANEWORLD SCENARIO is a recent development in M theory...that we live in a three brane..

Finally, Brian Greene's THE FABRIC OF THE COSMOS Chapter 13 "The Universe on a Brane" should be right up your alley...

 

[Abolhassan]

1- the brane tension corresponds to the vaccume energy on the brane, but it is not equal to the cosmological constant on the brane. I have read it recently from one paper. I want some information like that about tension of brane.

2- my second question is clear, I only like to know if the matter on bulk is confined to other brane or not. I am not good in string theory at all.

best wishes for all

 

[Naty1]

There are different kinds of branes...p branes in M theory extend beyond the usual idea of two dimensions...p dimensions are possible whole numbers in M theory up to 10. It turns out that p branes can be heavier than strings in some formulations...so they generally have more energy as in string theory energy is associated with mass. But research by guys like Smolin,Strominger and and Morrison showed that they do not have to be much heavier than strings...and in those cases a brane can wrap around a higher dimension...a Calabi Yau shape...

Polchinski showed that p branes have the right properties to grip open string end points, constraining them to move within the p dimensional space they occupy.

Above is from Chapter 13, FABRIC OF THE COSMOS