String GUTs
Abstract
Standard SUSYGUTS such as those based on SU(5) or SO(10) lead to predictions for the values of α _{s} and sin^{2}ϱ_{W} in amazing agreement with experiment. In this article we investigate how these models may be obtained from string theory, thus bringing them into the only known consistent framework for quantum gravity. String models with matter in standard GUT representations require the realization of affine Lie algebras at higher levels. We start by describing some methods to build level k = 2 symmetric orbifold string models with gauge groups SU(5) or SO(10). We present several examples and identify generic features of the type of models constructed. Chiral fields appropriate to break the symmetry down to the standard model generically appear in the massless spectrum. However, unlike in standard SUSYGUTs, they often behave as string moduli, i.e., they do not have selfcouplings. We also discuss briefly the doublettriplet Higgs splitting. We find that, in some models, builtin slidingsinglet type of couplings exist.
 Publication:

Nuclear Physics B
 Pub Date:
 February 1995
 DOI:
 10.1016/05503213(95)00282W
 arXiv:
 arXiv:hepth/9410206
 Bibcode:
 1995NuPhB.452....3A
 Keywords:

 High Energy Physics  Theory;
 High Energy Physics  Phenomenology
 EPrint:
 40 pages, Latex. Two references modified, few other unimportant changes