In this work, we investigate the multimode Brownian oscillators in
nonequilibrium scenarios with multiple reservoirs at different temperatures.
For this purpose, an algebraic method is proposed. This approach directly gives
the exact time-local equation of motion for reduced density operator, from
which we can easily extract both the reduced system and hybrid bath dynamical
informations. Two representative entangled system-bath quantities, the heat
transport and the thermodynamics of quantum mixing, are studied. The heat
current is obtained from both the algebraic method and the discrete
imaginary-frequency method followed by the Meir-Wingreen's formula. It is
anticipated that the algebraic method developed in this work would constitute a
crucial component for nonequilibrium statistical mechanics for open quantum
systems.Comment: SM adde