Fourth Generation t-prime in Extensions of the Standard Model

We study the effects of a fourth generation t-prime quark in various extensions of the standard model. In the Randall-Sundrum model, the decay t-prime -> t Z has a large branching ratio that could be detected at the Large Hadron Collider (LHC). We also look at the two-Higgs doublet models I, II and III, and note that, in the latter, the branching ratio of t-prime -> t H, where H is a Higgs scalar or pseudoscalar, is huge and we discuss detection at the LHC.