Structure of resistive networks for dispersive tunnel processes

Fundamental construction principles for equivalent circuits for superconducting pair and quasiparticle tunnel junctions are discussed. To the lowest order of microscopic tunneling, the two basic features of the corresponding macroscopic dynamics, i.e the energy-neutral nonlinear self-coupling of the quantum phase shift and the energy-effective tunnel admittance, are discussed in the framework of linear response theory (equivalent to the KUBO formalism) and are represented by means of the corresponding equivalent two-subcircuit network. Approximation formulas describing a singularity-equivalent model are discussed in detail, and consequences for secondary quantum processes are indicated