DM4 - Self Gravitating Systems and Dark Matter |
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Speaker |
Merafina, Marco |
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Coauthors |
Piscicchia, Kristian; Donnari Martina; Fragione Giacomo |
| Talk Title |
Gravity and Termodynamics in globular clusters. Theoretical developments and results by numerical simulations |
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Abstract |
New theoretical developments in the dynamical evolution of globular clusters (GC) and results by numerical simulations are presented. A new point of view in solving the Fokker-Planck equation describing the evolution of the stellar velocity distribution of a globular cluster can lead to a different way to obtain the solution and justify the introduction of the effective potential which describes the evaporation of stars due to tidal interactions between the cluster and the hosting galaxy. We also obtain new relations for the thermodynamical equilibrium in presence of gravity and introduce the concept of thermodynamic and kinetic temperature and pressure. The models present regions with positive and negative specific heat, producing thermodynamic instabilities which drive the clusters towards the so called gravothermal catastrophe. Moreover, new results on N-body simulations of isolated clusters without evaporation suggest a unique curve of relaxation before the disruption of the system, like in the case of low values of gravitation potential in the evolution of systems subjected to stellar evaporation. The critical value of the central gravitational potential after that the systems cannot be described by a King distribution function seems to be the same for every cluster and leads to generalized time functions characterizing the behavior of the main physical quantities. |
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