ELASTIC CONSEQUENCES OF THE DIELECTRIC BEHAVIOR OF YBA2CU3O7-DELTA

Owing to the fact that superconductivity can be described as a dielect ric phenomenon, where the screening of the repulsive electron-electron interaction is accounted for by introducing a temperature-dependent d ielectric function epsilon(omega, k), in this paper emphasis is put on a brief discussion of values of epsilon consistent with high supercon ducting transition temperatures in principle as well as on experimenta l techniques which allow determination of the temperature-dependence o f the dielectric function epsilon(omega, k).