# Tension brane

1. Feb 7, 2010

### alejandrito29

what means when the tension of our brane (universe-(t,x,y,z)) is:

- positive

- negative

- zero???????????

2. Feb 7, 2010

### torquil

Assuming that ours is a brane universe, brane tension will be interpreted by us as cosmological constant.

Torquil

3. Feb 7, 2010

### alejandrito29

i don't understand

the field equation is, for example:
$$(G_{mn}+\Lambda g_{mn})=\frac{\sqrt{h}}{\sqrt{g}}h_{uv}T\delta(w-w_0)$$

but , i think that $$\Lambda$$ is a cosmological constant.

¿what mean the tension $$T$$?

If $$T$$ does the same function that $$Lambda$$ then:

¿if T is positive then our universe is expanding?
¿if T is negative then our universe is contracting?
¿what abaut if T=0?

4. Feb 7, 2010

### torquil

You cannot say from the value of the lower dimensional effective cosmological constant alone if our 3D space is contracting, static or expanding with time. That would depend on initial conditions, and other field content.

The effective 4D brane cosmology will be described as having a cosmological constant which is contributed to by both the higher dimensional bulk cosmological constant, and the brane tension.

Here is a reference on brane cosmology, where you can find mathematical details, and other references:
http://arxiv.org/abs/hep-th/0209261/

Torquil