Reconciling grand unification with strings by anisotropic compactifications
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Date
2008-09-11
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American Physical Society
Abstract
We analyze gauge coupling unification in the context of heterotic strings on anisotropic orbifolds. This construction is very much analogous to effective five-dimensional orbifold grand unified theory field theories. Our analysis assumes three fundamental scales: the string scale M_S, a compactification scale M_C, and a mass scale for some of the vectorlike exotics M_EX; the other exotics are assumed to get mass at M_S. In the particular models analyzed, we show that gauge coupling unification is not possible with M_EX=M_C, and in fact we require M_EX«M_C~3×10^16 GeV. We find that about 10% of the parameter space has a proton lifetime (from dimension six gauge exchange) 10^33 yr =< t(p -> p^0 e^+) <= 10^36 yr. The other 80% of the parameter space gives proton lifetimes below Super-Kamiokande bounds. The next generation of proton decay experiments should be sensitive to the remaining parameter space.
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Ben Dundee, Stuart Raby, Akin Wingerter, "Reconciling grand unification with strings by anisotropic compactifications," Physical Review D 78, no. 6 (2008), doi:10.1103/PhysRevD.78.066006