Fr.: relaxation dynamique
The evolution over time of a gravitationally → bound system consisting of N components because of encounters between the components, as studied in → stellar dynamics. Due to this process, in a → star cluster, → low-mass stars may acquire larger random velocities, and consequently occupy a larger volume than → high-mass stars. As a result, massive stars sink to the cluster centre on a time-scale that is inversely proportional to their mass. See also → mass segregation.
Fr.: relaxation magnétique
The process by which a magnetic system relaxes to its minimum energy state over time.
Fr.: relaxation sans rayonnement
A process in which a molecule relaxes without emitting a → photon.
1) The evolution of the properties of a physical system which has
been disturbed and which regains its equilibrium condition
once the disturbing action has ceased. Relaxation is the response of the
system to the perturbation. The time required by the system to regain
its condition of minimum energy is called the
→ relaxation time.
Verbal noun of → relax.
Fr.: temps de relaxation
The characteristic length of time that is required for a system undergoing → relaxation to move to its equilibrium state. If the system follows an exponential law G = G0 exp(-t / τ), the relaxation time is the time required for G to obtain the fraction 1/e of its initial value G0.
Fr.: relaxation résonnante
A process whereby stellar orbit relaxation can be dramatically enhanced in orbits in a nearly Keplerian star cluster close to a → massive black hole (MBH). This process can modify the angular momentum distribution and affect the interaction rates of the stars with the MBH more efficiently than non-resonant relaxation. In the standard relaxation picture, each encounter is random and uncorrelated, so stars undergo a random walk. Relaxation is driven by the diffusion of energy which then leads to angular momentum transfer. However, in a stellar cluster around a MBH, each star will be on a Keplerian orbit, which is a fixed ellipse in space. The orbits of two nearby stars will thus exert correlated torques on one another, which can lead to a direct resonant evolution of the angular momentum. Since resonant relaxation increases the rate of angular momentum scattering, stars reach highly eccentric orbits more rapidly where they can become → extreme mass ratio inspiral (EMRI)s (Rauch, K.P., Tremaine, S., 1996, arXiv:astro-ph/9603018; Gair J.R. et al. 2013, Living Rev. Relativity, 16, (2013), 7 http://www.livingreviews.org/lrr-2013-7, doi:10.12942/lrr-2013-7).
Fr.: relaxation violente
A process in which a dynamical system made up of many objects (star cluster, galaxy cluster) rapidly relaxes from a chaotic initial state to a quasi-equilibrium.