Recently the author showed that in a superconductor the existence of scatterers like non-magnetic impurities or phonons in their long wavelength limit never limits the infinite ‘Ohmic’ conductivity which could be expected in the absence of those scatterers. In this paper we discuss the...

Linear response theory is extended to make it possible to treat nonlinear, and hence nonequilibrium, phenomena. Electric conductivity is discussed as an example of such nonlinear response, where a nonequilibrium distribution of quasiparticles might be established if an electric field of...