Determining and calculating spectroscopic factors from stable nuclei to the drip lines

A survey of our present understanding of absolute spectroscopic factors near stable closed-shell nuclei is given based on our current interpretation of the (e, e' p) reaction. Uncertainties associated with the imprecise knowledge of the degree of nonlocality of the optical potential of the knocked out proton are identified. Theoretical expectations for the dependence of spectroscopic factors on the nucleon asymmetry are outlined. Conflicting results obtained from various reactions concerning the asymmetry dependence of spectroscopic factors are surveyed. The possibility of obtaining reliable absolute spectroscopic factors with reactions initiated by hadrons is discussed with special emphasis on present and future radioactive beam experiments. The combined and integrated analysis of such reactions using a Green's function framework in the form of an extended dispersive optical model may provide a useful approach to resolve this theoretical open problem.