\left( t \right)} \\ {\frac{\partial\rho_{0}\left( t \right)}{\partial t} = - \rho_{0}\left( t \right) + \lambda^{\prime}{\langle k\rangle}s\left( t \right)\rho\left( t \right)} \\ {\frac{\partial\rho_{0}\left( t \right)}{\partial t} = - \rho_{0}\left( t \right) + \