Fluctuation and dissipation at a quantum critical point.

In nonrelativistic field theories, quantum fluctuations give rise to dissipative behavior 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 behavior 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.