A cluster version of the GGT sum rule

Abstract We discuss the derivation of a “cluster sum rule” from the Gellmann–Goldberger–Thirring (GGT) sum rule as an alternative to the Thomas–Reiche–Kuhn (TRK) sum rule, which was used as the basis up to now. We compare differences in the assumptions and approximations. Some applications of the sum rule for halo nuclei, as well as, nuclei with a pronounced cluster structure are discussed.