Probing the Flavor-Changing tc vertex via Tree-Level Processes: e+e- -> t bar-c nu_e bar-nu_e, t bar-c e+ e- and t -> c W+ W-

The reactions e+e- -> t bar-c nu_e bar-nu_e, t bar-c e+ e- are very sensitive probes of the flavor-changing-scalar couplings which can occur in a model with one extra Higgs doublet. At the Next Linear Collider, with a center of mass energy of sqrt{s}=0.5--2 TeV, several hundreds and up to thousands of such events may be produced if the mass of the light neutral Higgs is a few hundred GeV. We also briefly comment on the decays t -> c W+ W-, t -> c Z Z. All of these reactions are severely suppressed in the Standard Model