Extra Dimensions

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Among the most exciting ideas to have been raised in the theoretical physics community is that we may live in a universe with more dimensions of space than the three we experience. These "extra" dimensions could remain concealed from us for a variety of reasons. For example, they could be so small that only extremely energetic particles could fit in them. Alternatively, it could be that the kinds of matter we are made up of are confined to a multi-dimensional object called a brane. This would be analogous to something that was forced to reside on the surface of a tabletop, being unaware of any such thing as up or down. I am particularly interesting in how dark matter might be a consequence of the existence of extra spatial dimensions. In some models, ordinary particles traveling through an extra dimension of space can appear to us as stationary, but very heavy particles, called Kaluza-Klein modes. In models with what is known as Universal Extra Dimensions (UED), some of these Kaluza-Klein modes can be stable and may possibly constitute the dark matter of our universe. In addition to experiments looking for Kaluza-Klein modes in the form of dark matter, accelerator experiments such as the Tevatron and the Large Hadron Collider are also capable of searching for evidence that our universe possesses extra dimensions of space.