Fig. 1
From: Virtual photons in the ground state of a dissipative system
Eigenmodes of the Lorentz model. a Dispersion of the two polaritonic branches from the Lorentz model in Eq. (3), for ω c = 0.5ω 0 and γ L = 0 (thin blue lines), 0.5ω 0 (solid cyan lines), ω 0 (dash-dotted green lines), 1.5ω 0 (dashed magenta lines) and 2ω 0 (dotted red lines). The transition between the strong coupling regime presenting an anticrossing (blue and cyan lines) and the weak one in which the polaritonic modes cross (magenta and red lines), with the green line at the edge between the two, is cleary visible. b Trajectories drawn by the eigenfrequencies in the complex plane, at resonance ck = ω 0, when varying γ L. Coloured squares, triangles, dots, diamonds and circles mark the increasing values of γ L used in a
