| MadSci Network: Physics |
First, some background material for readers who are not familiar with all the terms in the question: http://en.wikipedia.org/wiki/Graviton http://en.wikipedia.org/wiki/Kaluza%E2%80%93Klein_theory http://en.wikipedia.org/wiki/Large_extra_dimensions http://en.wikipedia.org/wiki/String_theory The Kaluza-Klein (KK) modes above the zeroth mode are massive because one or more of the dimensions in which they can propagate is compact (curled up so that anything moving in that direction would return to its starting point). The zeroth mode particles are just the Standard Model (SM) particles, some of which are massless like the graviton. According to this theory, every SM particle that can move in the extra dimensions has heavier KK partners. http://profmattstrassler.com/articles-and-posts/some-speculative-theoretical-ideas-for-the-lhc/extra-dimensions/how-to-look-for-signs-of-extra-dimensions/ "Kaluza-Klein modes are particles predicted by the theory of large extra dimensions. They can propagate in the extra dimension, which is limited spatially to a very small radius. That small radius – the thickness of the extra dimension – is a spatial limit and through Heisenberg's uncertainty principle it implies a discrete spectrum of possible momentum states for the propagating bodies, just like quantum mechanics dictates that a particle in a box has a discrete spectrum of definite energies." http://dorigo.wordpress.com/2006/06/05/kaluza-klein-modes/ http://www-cdf.fnal.gov/PES/kkgrav/kkgrav.html In contrast, in the braneworld scenario, the extra space dimensions are not compact and the uncertainty principle does not impose a lower limit on the mass gap of the higher modes. "This spacetime also has oscillations in the extra dimension that are the Kaluza-Klein modes, but in this case there is a continuous spectrum of modes." http://www.superstringtheory.com/experm/exper5a1.html --Randall J. Scalise http://www.physics.smu.edu/scalise
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