9 large dimensions, No curled up ones?

[KeithClemens]

Any models worth checking out that do not rely on small curled up dimensions? And by large dimensions I don't mean 1mm, I mean all dimensions equally large.

 

[robousy]

Not that I know of. Even large (mm size) extra dimensions is kind of pushing it in the context of replacing one heirachy with another. You see, if the extra dimensions are large then we are immediately faced with phenomenological issues, i.e. where are they?

There are ways to 'hide' large extra dimensions. Sean Carroll came up with an interesting twist recently. http://arxiv.org/abs/0802.0521

The idea is to inject some generic field with a vev into the 5th dimension into a model.

In KK theory the momentum required to probe the extra dims is on the order of:

$$k\propto\frac{1}{r}$$

However, the existence of this lorentz violating field modifies the dispersion relations of say some scalar field and the momentum now reads:

$$k\propto\frac{(1+\alpha_\phi^2)}{r}$$

where $$\alpha_\phi$$ is the ratio of the vev of the field to its coupling parameter.

 

[Entropia]

There are several models in theoretical physics that do not rely on small curled up dimensions. One example is the holographic principle, which suggests that all the information in a three-dimensional space can be encoded on a two-dimensional surface. This eliminates the need for extra dimensions.

Another model is the brane-world scenario, which proposes that our universe is a four-dimensional brane embedded in a higher-dimensional space. In this model, all dimensions are equally large, but our perception is limited to four dimensions.

Additionally, the theory of loop quantum gravity suggests that space is made up of discrete units, rather than being continuous. This eliminates the need for extra dimensions to explain the behavior of particles at small scales.

Overall, there are several models worth exploring that do not rely on small curled up dimensions. These models provide alternative explanations for the behavior of particles and the structure of the universe. However, it is important for scientists to continue researching and testing these models in order to better understand the fundamental nature of our universe.