Total Muon-Capture Rate and the Consistency of Migdal's Theory

Migdal's theory of nuclear structure is recast in the shell-model language, enabling us to show that the excellent agreement with experiment of the theory applied to the total muon-capture rate is obtained by an appreciable symmetry breaking of the Wigner's SU(4) supermultiplet structure contrary to other models where the symmetry seems to be well preserved. Thus, the $\mu$-capture result is inconsistent with the dipole photoabsorption and inelastic electron scattering processes reflecting the possible breakdown of the quasiparticle hypothesis.