Gauge principle considerations and a new effect in pionic atoms

It is shown that the anomalous energy shifts in heavy pionic atoms may be explained by a gauge-generation of Coulomb terms in the s-wave π-nuclear optical potential without resorting to the energy dependence of the elementary amplitudes. The comparison with experiment is made in the 'standard' π-nuclear optical model whose parameters most closely agree with the microscopic theory. The anomaly persists for the widths. (orig.)