Christophe Pichon
Institut d'Astrophysique de Paris (Paris, France)
Amphithéâtre Henri Mineur, Institut d'Astrophysique de Paris
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| « Kinetic theory in galactic centers » |
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Christophe Pichon |
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I will review the formalism allowing for the description of the long-term evolution of a large set of particles orbiting a dominant massive object, such as in galactic nuclei. Because stars move in the quasi-Keplerian potential induced by the central black hole, their orbits can be approximated by ellipses whose orientations remain fixed over many dynamical times. Yet, on secular timescales, such a system will undergo a slow collisional relaxation driven by the remaining fluctuations in the system. When these fluctuations originate from the system intrinsic graininess (finite-N effects), the associated (scalar) resonant relaxation is captured by the (degenerate) inhomogeneous Balescu-Lenard equation. I will review in detail this kinetic formalism and emphasise the key physical mechanisms at play in this context. I will show in particular how one can account for the system's inhomogeneity (intricate trajectories), as well as the system's ability to amplify perturbations (self-gravity). I will finally show how such methods may be used to study the self-induced resonant relaxation of a discrete self-gravitating razor-thin axisymmetric disc orbiting a massive black hole, to recover for example the quenching of resonant diffusion in the vicinity of the black hole due to the divergence of the relativistic precessions.
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vendredi 2 février 2018 - 11:00 Amphithéâtre Henri Mineur, Institut d'Astrophysique de Paris |
| Page web du séminaire / Seminar's webpage |