In the superstring models we have not only the complete 27 multiplets of E_6 but also extra incomplete (27 + <27>^^-) chiral supermultiplets being alive at low energies. Associated with these additional multiplets, when the gauge symmetry contains more than one U(1) gauge group, there may exist gauge kinetic mixings among these U(1) gauge groups. In such cases the effect of gauge kinetic mixings should be incorporated into the study of unification of gauge couplings. We study these interesting effects systematically in these models. The string threshold effect is also taken into account. It is found that in the four-generation models we do not have a advisable solution of string unification of gauge couplings consistent with experimental values at the electroweak scale. We also discuss the possible scenarios to solve this problem.
雑誌名
Progress of theoretical physics
巻
90
号
4
ページ
895 - 910
発行年
1993
出版者
理論物理学刊行会
ISSN
0033-068X
書誌情報
Progress of theoretical physics. 1993, 90(4), p. 895-910.