Figure 4

Test function \(\Psi _{1,2}(\tau )\) defined in Eq. (33). (a) for \(\gamma '=10\) and (c) for \(\gamma '=0.6\). The role of the parameter \(\gamma '=2\gamma /\Omega \) appears when comparing (b) and (d) that display the two intercorrelation functions \(C_{FG}= \mathcal{C}_{I,I^{2}} (\tau )\) and \(C_{GF}=\mathcal{C}_{I^{2},I} (\tau )\). For strong damping the irreversible character is clearly visible in (b) where the solid and dashed curves are well separated. In (c) and (d) the damping is weaker, and so is the ratio \(\Psi _{12}/C_{FG} \), see text