Quantum indirect damping spectral densities

Note that this last expression is nothing but the closed form [90] of the autocorrelation function obtained (as an infinite sum) in quantum representation III by Boulil et al.[87] in their initial quantum approach of indirect damping. Although the small approximation involved in the quantum representation III and avoided in the quantum representation II, both autocorrelation functions are of the same form and lead to the same spectral densities (as discussed later). 

Moreover, the spectral density of the system involving both direct and indirect quantum damping, is the Fourier transform of Eq. (125), that is,... 

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