  In non-relativistic field theories, quantum fluctuations give rise to
dissipative behaviour even at zero temperature. Here we use holographic methods
to explore the dissipative dynamics of massive particles coupled to quantum
critical theories. We present analytic expressions for correlation functions
and response functions. The behaviour changes qualitatively as the dynamical
exponent passes through z = 2. In particular, for z > 2, the long time dynamics
of the particle is independent of its inertial mass.
