The GSI anomaly

Recently, an experiment at GSI Darmstadt has observed oscillating decay rates of heavy ions. Several controversial attempts have been made to explain this effect in terms of neutrino mixing. We briefly describe the experimental results, give an overview of the literature, and show that the effect cannot be due to neutrino mixing. If the effect survives, it could, however, be explained by hypothetical internal excitations of the mother ions (~ 10^(-15) eV).