On the various derivations of the energy dependence of the empirical optical potential

The predictions of the energy dependence of the real part of the empirical optical potential implied by the formulations based on nuclear reaction theories and on the multiple scattering approach are compared. The recent data on the nucleon-nucleon forward scattering amplitude obtained from phase-shift analyses, direct measurements and dispersion relations are used. The meaning of the local expression obtained in the multiple scattering formalism is discussed and it is shown that its implications agree with those derived by the nuclear-theories approach.