Studies of the closed core response to a perturbation in the Dirac Hamiltonian (due to an out-of-core baryon) are extended to particle-hole states in nuclear matter. Both isoscalar nucleon-particle–nucleon-hole states and Λ-particle–nucleon-hole hypernuclear states are considered. Core-response effects on the nuclear baryon current and the vector and scalar densities are studied, using both a perturbative treatment and linear response theory. While no essentially new physical insight is encountered by considering particle-hole states, there are many new and interesting applications. In particular, we mention applications to hypernuclei, meson-nucleus (especially ${\mathit{K}}^{+}$) interactions, meson photoproduction on nuclei, nuclear reactions, and nuclear transitions in inelastic scattering and weak interactions in nuclei. We point out interest in core-response effects related to nuclear transitions, where new physical insight is expected.

• Received 26 April 1993

DOI:https://doi.org/10.1103/PhysRevC.48.1346