  We develop novel methods to compute auto-correlation functions, or power
spectral densities, for chaotic dynamical systems generated by an inverse
method whose starting point is an invariant distribution and a two-form. In
general, the inverse method makes some aspects of chaotic dynamics calculable
by methods familiar in quantum field theory. This approach has the numerical
advantage of being amenable to Monte-Carlo parallel computation. We demonstrate
the approach on a specific example, and show how auto-correlation functions can
be computed without any direct numerical simulation, by Pade approximants of a
short time expansion.
