  We use the gauge-gravity duality conjecture to compute spectral functions of
the stress-energy tensor in finite temperature N=4 supersymmetric Yang-Mills
theory in the limit of large Nc and large coupling. The spectral functions
exhibit peaks characteristic of hydrodynamic modes at small frequency, and
oscillations at intermediate frequency. The non-perturbative spectral functions
differ qualitatively from those obtained in perturbation theory. The results
may prove useful for lattice studies of transport processes in thermal gauge
theories.
