Holographic heat engines

Abstract

It is shown that in theories of gravity where the cosmological constant is\nconsidered a thermodynamic variable, it is natural to use black holes as heat\nengines. Two examples are presented in detail using AdS charged black holes as\nthe working substance. We notice that for static black holes, the maximally\nefficient traditional Carnot engine is also a Stirling engine. The case of\nnegative cosmological constant supplies a natural realization of these engines\nin terms of the field theory description of the fluids to which they are\nholographically dual. We first propose a precise picture of how the traditional\nthermodynamic dictionary of holography is extended when the cosmological\nconstant is dynamical and then conjecture that the engine cycles can be\nperformed by using renormalization group flow. We speculate about the existence\nof a natural dual field theory counterpart to the gravitational thermodynamic\nvolume.\n