A note on the implications of causality for l-dependent potentials

We have examined the l-dependence of the real part of the 16O+16O potential which is required by causality as a result of surface transparency being represented by a partial wave cutoff in the imaginary potential, with energy-dependent parameters. The effect is strong, suggesting that the term arising from the dispersion correction needs to be included and that it may lead to an improvement in fitting scattering data for heavy-ion systems. This work also suggests that caution should be taken in relating phenomenological l-dependence of the real part to, for example, RGM effects.