Brane cosmology
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Brane cosmology refers to several theories in particle physics and cosmology motivated by, but not rigorously derived from, superstring theory and M-theory.
The central idea is that our visible, four-dimensional universe is entirely restricted to a brane inside a higher-dimensional space, called the bulk. The additional dimensions may be taken to be compact, in which case the observed universe contains the extra dimensions, and then no reference to the bulk is appropriate in this context. In the bulk model, other branes may be moving through this bulk. Interactions with the bulk, and possibly with other branes, can influence our brane and thus introduce effects not seen in more standard cosmological models.
As one of its attractive features, the model can explain the weakness of gravity relative to the other fundamental forces of nature, thus solving the so-called hierarchy problem. In the brane picture, the other three forces (electromagnetism and the weak and strong nuclear forces) are localised on the brane, but gravity has no such constraint and so much of its attractive power "leaks" into the bulk. As a consequence, the force of gravity should appear significantly stronger on small (sub-millimetre) scales, where less gravitational force has "leaked". Various experiments are currently underway to test this.[link]
The Randall-Sundrum, pre-big bang, ekpyrotic and cyclic scenarios are particular models of brane cosmology which have attracted a considerable amount of attention.
The theory hypothesises that the origin of the big bang could have occurred when two parallel branes touched.
See also
External links
- – Cosmological consequences of the brane world scenario are reviewed in a pedagogical manner.
- – These notes (32 pages) give an introductory review on brane cosmology.
- – Lectures (24 pages) presented at the First Aegean Summer School on Cosmology, Samos, September 2001.
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