Spectral density Ohmic dissipation

The formal structure of (5.77) suggests that the reaction coordinate Q can be combined with the bath coordinates to form a new fictitious bath , so that the Hamiltonian takes the standard form of dissipative TLS (5.55). Suppose that the original spectrum of the bath is ohmic, with friction coefficient q. Then diagonalization of the total system (Q, qj ) gives the new effective spectral density [Garg et al. 1985]... 

To make further progress, it is standard practice to take this definition of the spectral density and replace it by a continuous form based on physical intuition. A form that is often used for the spectral density is a product of ohmic dissipation qco (which corresponds to Markovian dynamics) times an exponential cutoff (which reflects the fact that frequencies of the normal modes of a finite system have an upper cutoff) ... 

The formal similitude between Eq. (30) and Ohm s law in an electrical circuit justifies the term of Ohmic model given to the dissipation model as defined by the spectral density (23). 

Here we apply the LAND-map approach to compute of the time dependent average population difference, A t) = az t)), between the spin states of a spin-boson model. Here az = [ 1)(1 — 2)(2 ]. Within the limits of linear response theory, this model describes the dissipative dynamics of a two level system coupled to an environment [59,63-65]. The environment is represented by an infinite set of harmonic oscillators, linearly coupled to the quantum subsystem. The characteristics of the system-bath coupling are completely described by the spectral density J(w). In the following, we shall restrict ourselves to the case of an Ohmic spectral density... 

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See also in sourсe #XX -- [ ]

See also in sourсe #XX -- [ ]

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