t -> cWW and WW -> anti tc + t anti c in extended models

Jenkins has pointed out that the process t rarrow cW+W-is GIM suppressed in the standard model. In this note, the authors calculate the branching ratio for a wide range of models, in which the decay occurs at tree level through exchange of a scalar, fermion or vector. In the case of scalar exchange, a scalar mass between 2mW and 200 GeV leads to a resonant enhancement, giving a branching ratio as high as a few tenths of a percent. They then note that all of these models will also allow W+W- rarrow anti tc + t anti c, and they calculate the single-top/single-charm production rate at the LHC. The rates aren't negligibly small, but the background from single-top/single-bottom production will probably swamp the signal