Physics – High Energy Physics – High Energy Physics - Theory
Scientific paper
2008-06-04
Nucl.Phys.B810:316-353,2009
Physics
High Energy Physics
High Energy Physics - Theory
56 pages; v2. minor corrections, v3. a short discussion on proton-decay enhancement factor is added
Scientific paper
10.1016/j.nuclphysb.2008.11.009
Wilson line on a non-simply connected manifold is a nice way to break SU(5) unified symmetry, and to solve the doublet--triplet splitting problem. This mechanism also requires, however, that the two Higgs doublets are strictly vector-like under all underlying gauge symmetries, and consequently there is a limit in a class of modes and their phenomenology for which the Wilson line can be used. An alternative is to turn on a non-flat line bundle in the U(1)_Y direction on an internal manifold, which does not have to be non-simply connected. The U(1)_Y gauge field has to remain in the massless spectrum, and its coupling has to satisfy the GUT relation. In string theory compactifications, however, it is not that easy to satisfy these conditions in a natural way; we call it U(1)_Y problem. In this article, we explain how the problem is solved in some parts of moduli space of string theory compactifications. Two major ingredients are an extra strongly coupled U(1) gauge field and parametrically large volume for compactification that is also essential in accounting for the hierarchy between the Planck scale and the GUT scale. Heterotic-M theory vacua and F-theory vacua are discussed. This article also shows that the toroidal orbifold GUT approach using discrete Wilson lines corresponds to the non-flat line-bundle breaking above when orbifold singularities are blown up. Thus, the orbifold GUT approach also suffers from the U(1)_Y problem, and this article shows how to fix it.
Tatar Radu
Watari Taizan
No associations
LandOfFree
GUT Relations from String Theory Compactifications does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with GUT Relations from String Theory Compactifications, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and GUT Relations from String Theory Compactifications will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-153737