  One of the most exciting things in recent theoretical physics is the
suspicion that gravity may be holographic, dual to some sort of quantum field
theory living on the boundary with one less dimension. Such a suspicion has
been supported mainly by a variety of specific examples from string theory.
This paper is intended to purport the holographic gravity from a different
perspective. Namely we propose that such a holography can actually be observed
within the context of Einstein's gravity, where neither is spacetime required
to be asymptotically AdS nor the boundary to be located at conformal infinity.
We show that our holography works remarkably well at least at the level of
thermodynamics and hydrodynamics. In particular, a perfect matching between the
bulk gravity and boundary system is found not only for the equilibrium
variation but also for the non-equilibrium entropy production, where a method
of conserved current is seen to be efficient in relating the black hole
perturbation in the bulk gravity and the non-equilibrium thermodynamics on the
boundary.
