Black hole thermodynamics and heat engines in conformal gravity

Abstract

The extended phase space thermodynamics and heat engines for static spherically symmetric black hole solutions of four dimensional conformal gravity are studied in detail. It is argued that the equation of states (EOS) for such black holes is always branched, any continuous thermodynamical process cannot drive the system from one branch of the EOS into another branch. Meanwhile, the thermodynamical volume is bounded from above, making the black holes always super-entropic in one branch and may also be super-entropic in another branch in certain range of the temperature. The Carnot and Stirling heat engines associated to such black holes are shown to be distinct from each other. For rectangular heat engines, the efficiency always approaches zero when the rectangle becomes extremely narrow, and given the highest and lowest working temperatures fixed, there is always a maximum for the efficiency of such engines.Comment: 21 pages, 10 figures. To appear in IJMP

Black hole evaporation in Lovelock gravity with diverse dimensions

“…The pure AdS space-time, corresponding to M = − 1 2G k , cannot be reached just by black hole evaporation process. The second one is the difference from conformal (Weyl) gravity [41,42], where a final state with vanishing temperature that cannot be achieved in finite time also exists. However, in conformal (Weyl) gravity the final state corresponds to an extremal black hole with finite size, while in our case it corresponds to r + → 0.…”

Effects of quantum corrections on the criticality and efficiency of black holes surrounded by a perfect fluid

“…We shall analyze the effect of quantum corrections on the efficiency of some processes for different perfect fluids surrounding the black hole. This framework was first idealized by Johnson [27] and has been explored in different contexts [28][29][30][31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46]. This paper is organized in the following way.…”

Black hole evaporation in conformal (Weyl) gravity

“…The difference in the actions means that the black-hole thermodynamics of the two gravity theories would be different. The thermodynamic phase structure for the conformal gravity in the four-dimensional AdS space-time * xuh5@sustc.edu.cn has been explored [9][10][11][12]; the phase structure of the conformal gravity includes two branches of equations of states, zeroth-order phase transition, and Hawking-Pagelike phase transition.…”

“…We start by giving a brief review of the black hole thermodynamics in conformal gravity [9][10][11][12]. The gravity action is proportional to the square of the Weyl tensor,…”

“…Note that the entropy depends on a combination of c 0 , r 0 and d, rather than just being proportional to the area of the horizon [9]. Furthermore, the first law of black hole thermodynamics and the Smarr formula in extended phase space have been investigated in [9][10][11][12] and will not be covered here. Now, applying f (r 0 ) = 0 and (4) to eliminate other unnecessary coefficients, we found that the equations of states are branched [11].…”