Gravity and thermodynamics: fundamental principles and gravothermal instability

Abstract

Globular clusters are stellar systems in which thermodynamics plays a fundamental role. Classically these systems are described by non-relativistic single mass King distribution function, which derives from the Fokker-Planck equation by taking into account stellar collisions and host galaxy tidal confinement. In terms of statistical mechanics the available phase space is restricted and so thermodynamics variables assume different meaning respect to the Boltzmann distribution. Through the introduction of an effective potential, which stands for the galactic tidal forces, a new thermodynamic theory is developed and theoretical energy and specific heat profiles are given for globular clusters.