The statistical mechanics of self-gravitating Keplerian discs (Q2874757)

The authors describe the dynamics and thermodynamics of collisionless particle discs orbiting a massive central body. They consider a case, where the disc mass is small compared to the central mass, the self-gravity of the disc dominates the non-Keplerian force, and the spread in the semi-major axes is small. By means of plausible approximations it is established that such discs have logarithmic two-body interactions and a compact phase space, and exhibit thermodynamics that are simpler than most other gravitating systems. The authors are able to solve the microcanonical axisymmetric thermal equilibria and demonstrate the existence of a symmetry-breaking bifurcation into lopsided equilibria.