Spectral shape dependence in the very strong coupling regime of Eliashberg theory

The effect of ²F() shape dependence on several physical properties of superconductors is studied at various values of the strong coupling indexT_c/_ln. Our results indicate that the degree of shape dependence of each property is sensitive to the value ofT_c/_ln. Generally, for the region we examine, 0.25T_c/_ln1.3, the dependence on shape is found to be higher than in the conventional strong coupling regimeT_c/_ln0.2. However, with the exception of the mass enhancement parameter , the amount of shape dependence does not increase steadily withT_c/_ln and there appears to be regions of maximum shape sensitivity.