2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/200193The neutron-proton mass difference in finite nuclei is studied in the framework of a medium-modified Skyrme model. The possible interplay between the effective nucleon mass in finite nuclei and the Nolen-Schiffer anomaly is discussed. In particular, we find that a correct description of the properties of mirror nuclei leads to a stringent restriction of possible modifications of the nucleon's effective mass in nuclei.13 pages, 6 figures (some typos corrected and references added)Nuclear Theorytext