  We present a framework for analyzing black hole backreaction from the point
of view of quantum open systems using influence functional formalism. We focus
on the model of a black hole described by a radially perturbed quasi-static
metric and Hawking radiation by a conformally coupled massless quantum scalar
field. It is shown that the closed-time-path (CTP) effective action yields a
non-local dissipation term as well as a stochastic noise term in the equation
of motion, the Einstein-Langevin equation. Once the thermal Green's function in
a Schwarzschild background becomes available to the required accuracy the
strategy described here can be applied to obtain concrete results on
backreaction. We also present an alternative derivation of the CTP effective
action in terms of the Bogolyubov coefficients, thus making a connection with
the interpretation of the noise term as measuring the difference in particle
production in alternative histories.
