Revisiting relaxation in globular clusters
The classical theory of cluster relaxation is unsatisfactory because it involves the Coulomb logarithm. The Balescu–Lenard (BL) equation provides a rigorous alternative that has no ill-defined parameter. Moreover, the BL equation, unlike classical theory, includes the cluster’s self-gravity. A heuri...
| Main Authors: | , , , |
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| Format: | Journal article |
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Oxford University Press
2018
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| _version_ | 1826266178938470400 |
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| author | Hamilton, C Fouvry, J Binney, J Pichon, C |
| author_facet | Hamilton, C Fouvry, J Binney, J Pichon, C |
| author_sort | Hamilton, C |
| collection | OXFORD |
| description | The classical theory of cluster relaxation is unsatisfactory because it involves the Coulomb logarithm. The Balescu–Lenard (BL) equation provides a rigorous alternative that has no ill-defined parameter. Moreover, the BL equation, unlike classical theory, includes the cluster’s self-gravity. A heuristic argument is given that indicates that relaxation does not occur predominantly through two-particle scattering and is enhanced by self-gravity. The BL equation is adapted to a spherical system and used to estimate the flux through the action space of isochrone clusters with different velocity anisotropies. A range of fairly different secular behaviours is found depending on the fraction of radial orbits. Classical theory is also used to compute the corresponding classical fluxes. The BL and classical fluxes are very different because (a) the classical theory materially underestimates the impact of large-scale collectively amplified fluctuations and (b) only the leading terms in an infinite sum for the BL flux are computed. A complete theory of cluster relaxation likely requires that the sum in the BL equation be decomposed into a sum over a finite number of small wavenumbers complemented by an integral over large wavenumbers analogous to classical theory. |
| first_indexed | 2024-03-06T20:34:59Z |
| format | Journal article |
| id | oxford-uuid:3253d3ce-61c1-4f16-884c-6a240c31333c |
| institution | University of Oxford |
| last_indexed | 2024-03-06T20:34:59Z |
| publishDate | 2018 |
| publisher | Oxford University Press |
| record_format | dspace |
| spelling | oxford-uuid:3253d3ce-61c1-4f16-884c-6a240c31333c2022-03-26T13:13:19ZRevisiting relaxation in globular clustersJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:3253d3ce-61c1-4f16-884c-6a240c31333cSymplectic Elements at OxfordOxford University Press2018Hamilton, CFouvry, JBinney, JPichon, CThe classical theory of cluster relaxation is unsatisfactory because it involves the Coulomb logarithm. The Balescu–Lenard (BL) equation provides a rigorous alternative that has no ill-defined parameter. Moreover, the BL equation, unlike classical theory, includes the cluster’s self-gravity. A heuristic argument is given that indicates that relaxation does not occur predominantly through two-particle scattering and is enhanced by self-gravity. The BL equation is adapted to a spherical system and used to estimate the flux through the action space of isochrone clusters with different velocity anisotropies. A range of fairly different secular behaviours is found depending on the fraction of radial orbits. Classical theory is also used to compute the corresponding classical fluxes. The BL and classical fluxes are very different because (a) the classical theory materially underestimates the impact of large-scale collectively amplified fluctuations and (b) only the leading terms in an infinite sum for the BL flux are computed. A complete theory of cluster relaxation likely requires that the sum in the BL equation be decomposed into a sum over a finite number of small wavenumbers complemented by an integral over large wavenumbers analogous to classical theory. |
| spellingShingle | Hamilton, C Fouvry, J Binney, J Pichon, C Revisiting relaxation in globular clusters |
| title | Revisiting relaxation in globular clusters |
| title_full | Revisiting relaxation in globular clusters |
| title_fullStr | Revisiting relaxation in globular clusters |
| title_full_unstemmed | Revisiting relaxation in globular clusters |
| title_short | Revisiting relaxation in globular clusters |
| title_sort | revisiting relaxation in globular clusters |
| work_keys_str_mv | AT hamiltonc revisitingrelaxationinglobularclusters AT fouvryj revisitingrelaxationinglobularclusters AT binneyj revisitingrelaxationinglobularclusters AT pichonc revisitingrelaxationinglobularclusters |