  The effect of low energy excitation on the dynamics of Josephson phase in SNS
junction is investigated. From the microscopic Hamiltonian, the effective
action for the phase variable is derived. The retardation effects due to low
energy excitation in normal(N) region are seen to play important roles in the
dynamics of the phase. By the self consistent harmonic approximation,
renormalization of mass and dissipation constant are calculated, revealing the
enhancement of the former and the suppression of the latter in general. Various
situation appears depending on these renormalized values.

Superconductivity