Constraints on top-quark flavor changing neutral couplings from electroweak precision measurements -: art. no. 057504

We study the one-loop contributions of the effective flavor changing neutral couplings (FCNC) tcZ, tcH, and tc gamma on the electroweak precision observables Gamma(Z),R-c,R-b,R-center dot,A(c), and A(c)(FB), as well as the oblique parameters S and T. Using the known experimental limits on these observables, we may place 95% C.L. bounds on these FCNC couplings which in turn translate into the following limits for the branching ratios BR(t -> cZ)<= 1.6x10(-2) and BR(t -> cH)<=(0.09-2.8)x10(-3) for 114 <= m(H)<= 170 GeV.