  Einstein equations projected on to a black hole horizon gives rise to
Navier-Stokes equations. Horizon-fluids typically possess unusual features like
negative bulk viscosity and it is not clear whether a statistical mechanical
description exists for such fluids. In this work, we provide an explicit
derivation of the Bulk viscosity of the horizon-fluid based on the theory of
fluctuations a la Kubo. The main advantage of our approach is that our analysis
remains for the most part independent of the details of the underlying
microscopic theory and hence the conclusions reached here are model
independent. We show that the coefficient of bulk viscosity for the
horizon-fluid matches exactly with the value found from the equations of motion
for the horizon-fluid.
