Flat Directions in $Z_{2n}$ Orbifold Models

Abstract

We study generic features related to matter contents and flat directions in $Z_{2n}$ orbifold models. It is shown that $Z_{2n}$ orbifold models have massless conjugate pairs, $R$ and $\overline{R}$, in certain twisted sectors as well as one of untwisted subsectors. Using these twisted sectors, $Z_{2n}$ orbifold models are classified into two types. Conjugate pairs, $R$ and $\overline{R}$, lead to $D$-flatness as $⟨R⟩=⟨\overline{R}⟩\ne 0$. We investigate generic superpotentials derived from orbifold models so as to show that this direction is indeed a flat direction.

Comments: 43 pages, latex, no figures