In physics, Randall-Sundrum models imagine that the real world is a higher-dimensional Universe described by warped geometry. More concretely, our Universe is a five-dimensional anti de Sitter space and the elementary particles except for the graviton are localized on a (3 + 1)-dimensional brane or branes.
The models were proposed in 1999 by Lisa Randall and Raman Sundrum while studying technicolor models.
With the online chat yesterday I'll have to look in on Sabine Hossenfelder and Stefan's of Backreaction blog entry in this regard to look at it more in depth.
Photograph by Phil Knott
Click to view for a larger version.So you intuitively believe higher dimensions really exist?
I don't see why they shouldn't. In the history of physics, every time we've looked beyond the scales and energies we were familiar with, we've found things that we wouldn't have thought were there. You look inside the atom and eventually you discover quarks. Who would have thought that? It's hubris to think that the way we see things is everything there is.
If there are more than three dimensions out there, how does that change our picture of the universe?
The very ideas are of extra dimensions are very progressive, and are not without some history. Some people will label anything as crackpot, without understanding the history of these discussions."
Physics strings us along by Margaret Wertheim of LAtimes.com
In the latest, hottest Big Science tome — the delightfully titled "Warped Passages" — Harvard physicist Lisa Randall describes the idea that the universe we see around us is but one tiny part of a vast reality that may include an infinite number of other universes. Randall is an expert on both cosmology and that arcane branch of particle physics known as string theory. By marrying the two fields, she and her colleagues have formulated a picture in which our universe may be seen as a soap-film-like membrane (a "braneworld") sitting inside a much larger space: the bulk. According to general relativity, the universe we live in has four dimensions: three of space and one of time. Randall's work extends this framework and posits the existence of a fifth dimension. The fifth dimension is the bulk, and within its immeasurably expanded space, there is no reason to assume that ours is the only cosmos.
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