Nonequilibrium Brownian dynamics

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Brownian Dynamics Classical Dynamics of Nonequilibrium Processes in Fluids Classical Trajectory Simulations Final Conditions Molecular Dynamics Techniques and Applications to Proteins. 

It is essential to understand that the aforementioned dynamical randomness is quantitatively comparable to the one seen in Brownian motion or other stochastic processes of nonequilibrium statistical mechanics. Indeed, the dynamical... 

The fluctuating variables aie thereby projected onto pair-density fluctuations, whose time-dependence follows from that of the transient density correlators q(,)(z), defined in (12). Tliese describe the relaxation (caused by shear, interactions and Brownian motion) of density fluctuations with equilibrium amplitudes. Higher order density averages are factorized into products of these correlators, and the reduced dynamics containing the projector Q is replaced by the full dynamics. The entire procedure is written in terms of equilibrium averages, which can then be used to compute nonequilibrium steady states via the ITT procedure. The normalization in (10a) is given by the equilibrium structure factors such that the pair density correlator with reduced dynamics, which does not couple linearly to density fluctuations, becomes approximated to ... 

A different formahsm in which the diffusion of a Brownian gas in a fluid under stationary and non-stationary flow has been analyzed is mesoscopic nonequilibrium thermodynamics (MNET) (Perez-Madrid, 1994 Rubi Mazur, 1994 Rubi P rez-Madrid, 1999). This theory uses the nonequUibrium thermodynamics rules in the phase space of the system, and allows to derive Fokker-Planck equations that are coupled with the thermodynamic forces associated to the interaction between the system and the heat bath. The effects of this coupling on system s dynamics are not obvious. This is the case of Brownian motion in the presence of flow where, as we have discussed previously, both the diffusion coefficient and the chemical potential become modified by the presence of flow (Reguera Rubi, 2003a b Santamaria Holek, 2005 2009 2001). 

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