Anomalies in weak decays of H-like ions

We investigate the emergence of oscillations in the decay law of unstable systems. We discuss in particular the case of the so-called GSI anomaly seen in the electron capture decays of H-like ions and prove that such oscillations cannot be explained by neutrino oscillations. We then discuss how such anomalies could be intimately related to the decay law of unstable systems in the case in which their spectral function deviates from a Breit-Wigner shape.