Frequency evolution of neutron peaks below Tc:: Commensurate and incommensurate structure in La0.85Sr0.15CuO4 and YBa2Cu3O6.6

We study the evolution of the neutron cross section with variable frequency omega and fixed T below T-c in two different cuprate families. Our calculations, which predominantly probe the role of d-wave pairing, lend to generic features, independent of Fermi-surface shapes. Among our findings, reasonably consistent with experiment, are (i) for omega near the gap energy Delta, both optimal LaO0.85Sr0.15CuO4 and slightly underdoped YBa2Cu3O6.6 exhibit (comparably) incommensurate peaks, (ii) peak sharpening below T-c is Seen in LaSrCuO, and (iii) quite generically, a frequency evolution from incommensurate to commensurate and then back to incommensurate structure is found with increasing omega. Due to their narrow omega regime of stability, commensurate peaks in LaSrCuO should be extremely difficult to observe.