Global and local thermodynamics of the (2+1)-dimensional rotating Gauss-Bonnet black hole

The aim of this paper is to study the local and the global thermodynamic properties of the threedimensional rotating Gauss-Bonnet black hole. To this end we consider the conditions for local and global thermodynamic stability of the solution in a given ensemble of state quantities. Concerning the local analysis we found the regions of stability for every physical specific heat together with the existing Davies curves. Another central result is the generalization of the notion of global thermodynamic stability, known from the standard thermodynamics, to describe the global equilibrium of black holes. The new approach consists of applying specific Legendre transformation of the energy or the entropy to find the natural thermodynamic potential for the given ensemble of macro parameters. The global stability analysis, restricted to the week positivity conjecture, is based on the properties of the new thermodynamic potential. The advantage of this method is that it allows one to chose different potentials, corresponding to different constraints to which the system may be subjected. Finally, we find it natural to impose global thermodynamic stability only where a local one exists for the given black hole solution.