Holographic heat engines and static black holes: a general efficiency formula.
Starting from simple observations regarding heat flows for static black holes (or any thermodynamic system with $C_V=0$), we get some inequalities restricting their change in energy and adiabatic curves in the $p-T$ plane. From these observations we then derive an exact efficiency formula for virtually any holographic heat engine defined by a cycle in the $p-V$ plane, whose working substance is a static black hole. Moreover, we get a universal upper bound for its efficiency and show that it is achieved by an "ideal gas" hole. Finally, we compute exact efficiencies for some particular and new engines.
Publisher URL: http://arxiv.org/abs/1801.07425