  We study the dissipative dynamics of a harmonic oscillator which couples
linearly through its position and its momentum to two independent heat baths at
the same temperature. We argue that this model describes a large spin in a
ferromagnet. We find that some effects of the two heat baths partially cancel
each other. This leads to unexpected features such as underdamped oscillations
and long relaxation times in the strong coupling regime. Such a partial
frustration of dissipation can be ascribed to the canonically conjugate
character of position and momentum. We compare this model to the scenario where
a single heat bath couples linearly to both the position and the momentum of
the central oscillator. In that case less surprising behavior occurs for strong
coupling. The dynamical evolution of the quantum purity for a single and a
double wave packet is also investigated.
