Drude-conductivity pole sigma(omega) = sigma_0/(1 - i omega tau); meromorphic

Drude-conductivity dispersion framework (Drude 1900 Annalen der Physik 1, 566). Setup: free-electron response to AC electric field σ(ω) = σ_0/(1 - i ω τ), with σ_0 = n e² τ/m the DC conductivity (n carrier density, τ relaxation time). At…