Bridging k- and q- Space in the Cuprates: Comparing ARPES and STM Results

A critical comparison is made between the ARPES-derived spectral function and STM studies of Friedel-like oscillations in Bi_2Sr_2CaCu_2O_{8+delta} (Bi2212). The data can be made approximately consistent, provided that (a) the elastic scattering seen in ARPES is predominantly small-angle scattering and (b) the peak' feature seen in ARPES is really a dispersive bright spot’, smeared into a line by limited energy resolution; these are the `bright spots’ which control the quasiparticle interferences. However, there is no indication of bilayer splitting in the STM data.