Hello, I'm trying to make a sort of "system theory approach" to dynamic Maxwell's equations for a linear, isotropic, time-invariant, spacely homogeneous medium. The frequency-domain uniqueness theorem states that the solution to an interior electromagnetic problem is unique for a lossy medium; but if the medium is lossless, then there can be "resonant solutions". The above-mentioned unique frequency-domain solution should return, in the time-domain, the steady-state response of the electromagnetic field to a sinusoidal source. What do resonant solutions return in the time-domain? Let the electromagnetic field be forced, in a lossy medium, at a resonance frequency: would the solution be unique? If the phasor-domain uniqueness theorem returns the steady-state response, does the time-domain one return the zero-input response as well? Thanks in advance for your help.