# The Bulk and time.

1. Dec 11, 2008

### Dmitry67

My question is naive and may be incorrectly formulated

So, the bulk: http://en.wikipedia.org/wiki/Brane_cosmology
which is constantly producing 'hubble spaces'.

I wounder if there is 'Time' in the Bulk. If there is time, does in point to the same direction as in the hubble spaces. If not, how the new bubbles can appear.

Also, what exactly makes the parameters of the Standard model different in different bubbles. Can the number of dimensions be different? Can there be more then 1 time dimension?

Thank you

2. Dec 11, 2008

### derek.basler

Well I'm not really knowledgable about Brane Theories. I know a lot about string theory, but not so much about branes. However, it seems that your question is really dealing with the time dimension. Its interesting to think of multi-time dimensions, however, you cannot think of time in the same way as spacial dimensions. Time does go forward and in theory, backward, but that is simply one dimension. I really dont think there are other ways for time to move, such as with space which could go up and down side to side, etc. And a lot of the mathematics show that the multi-dimensions are spacial dimensions, most likely Calabi-Yau Manifolds, which are shown here

http://universe-review.ca/I15-15-CalabiYauSpace.jpg

But its very interesting to think about, and would certainly be cool. I once had an idea that what if time where two dimensional, would that be able to partially explain why a particle can appear in two places at the same time on a very short scale, wave-particle duality pretty much? It's just a thought though.

3. Dec 16, 2008

### Coin

I do not understand string theory well, but I've seen models where "time" in our universe is described as just a property of the brane our universe is stuck to-- such that the brane happens to curve in such a way that our spacetime has a "signature" of three spacelike and one timelike dimensions. But other branes within the bulk might have no timelike dimensions, or more than one timelike dimension, depending on what their signature is.

The existence of models where the "timelikeness" of dimensions is determined by the properties of the brane seems to me to imply that braneworld models do not have a preferred "time" dimension or direction.

4. Dec 16, 2008

### Dmitry67

Thank you
So time belongs to a brane?
Hence, there is no time in the bulk?
If so, I see the problem with the initial conditions because the configuration of the bulk (including the positions of all branes) must be predefined.