Poor man's holography: How far can it go?

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.Comment: This essay received an honorable mention in the 2012 Essay Competition of the Gravity Research Foundation. 12 pages, revtex4; v2: slight improvement on presentation in section 3, typos fixed; v3: holographic derivation of the first law of thermodynamics in section 2 is clarified and strengthene