Isotropic–nematic phase transitions in gravitational systems
We examine dense self-gravitating stellar systems dominated by a central potential, such as nuclear star clusters hosting a central supermassive black hole. Different dynamical properties of these systems evolve on vastly different timescales. In particular, the orbital-plane orientations are typica...
| Main Authors: | , , |
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| Format: | Journal article |
| Language: | English |
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IOP Publishing
2017
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| _version_ | 1826283833301925888 |
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| author | Roupas, Z Kocsis, B Tremaine, S |
| author_facet | Roupas, Z Kocsis, B Tremaine, S |
| author_sort | Roupas, Z |
| collection | OXFORD |
| description | We examine dense self-gravitating stellar systems dominated by a central potential, such as nuclear star clusters hosting a central supermassive black hole. Different dynamical properties of these systems evolve on vastly different timescales. In particular, the orbital-plane orientations are typically driven into internal thermodynamic equilibrium by vector resonant relaxation before the orbital eccentricities or semimajor axes relax. We show that the statistical mechanics of such systems exhibit a striking resemblance to liquid crystals, with analogous ordered-nematic and disordered-isotropic phases. The ordered phase consists of bodies orbiting in a disk in both directions, with the disk thickness depending on temperature, while the disordered phase corresponds to a nearly isotropic distribution of the orbit normals. We show that below a critical value of the total angular momentum, the system undergoes a first-order phase transition between the ordered and disordered phases. At a critical point, the phase transition becomes second order, while for higher angular momenta there is a smooth crossover. We also find metastable equilibria containing two identical disks with mutual inclinations between 90° and 180°. |
| first_indexed | 2024-03-07T01:04:47Z |
| format | Journal article |
| id | oxford-uuid:8af4baa5-68ed-4005-93b9-e1b7a8b9598c |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T01:04:47Z |
| publishDate | 2017 |
| publisher | IOP Publishing |
| record_format | dspace |
| spelling | oxford-uuid:8af4baa5-68ed-4005-93b9-e1b7a8b9598c2022-03-26T22:34:59ZIsotropic–nematic phase transitions in gravitational systemsJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:8af4baa5-68ed-4005-93b9-e1b7a8b9598cEnglishSymplectic ElementsIOP Publishing2017Roupas, ZKocsis, BTremaine, SWe examine dense self-gravitating stellar systems dominated by a central potential, such as nuclear star clusters hosting a central supermassive black hole. Different dynamical properties of these systems evolve on vastly different timescales. In particular, the orbital-plane orientations are typically driven into internal thermodynamic equilibrium by vector resonant relaxation before the orbital eccentricities or semimajor axes relax. We show that the statistical mechanics of such systems exhibit a striking resemblance to liquid crystals, with analogous ordered-nematic and disordered-isotropic phases. The ordered phase consists of bodies orbiting in a disk in both directions, with the disk thickness depending on temperature, while the disordered phase corresponds to a nearly isotropic distribution of the orbit normals. We show that below a critical value of the total angular momentum, the system undergoes a first-order phase transition between the ordered and disordered phases. At a critical point, the phase transition becomes second order, while for higher angular momenta there is a smooth crossover. We also find metastable equilibria containing two identical disks with mutual inclinations between 90° and 180°. |
| spellingShingle | Roupas, Z Kocsis, B Tremaine, S Isotropic–nematic phase transitions in gravitational systems |
| title | Isotropic–nematic phase transitions in gravitational systems |
| title_full | Isotropic–nematic phase transitions in gravitational systems |
| title_fullStr | Isotropic–nematic phase transitions in gravitational systems |
| title_full_unstemmed | Isotropic–nematic phase transitions in gravitational systems |
| title_short | Isotropic–nematic phase transitions in gravitational systems |
| title_sort | isotropic nematic phase transitions in gravitational systems |
| work_keys_str_mv | AT roupasz isotropicnematicphasetransitionsingravitationalsystems AT kocsisb isotropicnematicphasetransitionsingravitationalsystems AT tremaines isotropicnematicphasetransitionsingravitationalsystems |