Flavor-Changing Neutral Currents Induced by the Democratic Seesaw Mass Matrix

Flavor-changing neutral currents (FCNC) are studied on the basis of a ``democratic seesa'' mass matrix model, which yields a singular enhancement of the top-quark mass m_t and can give reasonable quark masses and CKM matrix elements. The most exciting aspect of the model is that the structure of the $6 \times 6$ right-handed fermion mixing matrix in the up-quark sector, $U^R_u$, shows an abnormal structure in contrast to that of $U^L_u$. This causes characteristic effects on the right-handed FCNC concerned with top quark. A single top-quark production at future $e^+ e^-$ colliders, $e^+ + e^- \to Z_R \to t + \overline{c}$ ($\overline{t}+c$), is discussed.