364 research outputs found
Local virial relation and velocity anisotropy for collisionless self-gravitating systems
The collisionless quasi-equilibrium state realized after the cold collapse of
self-gravitating systems has two remarkable characters. One of them is the
linear temperature-mass (TM) relation, which yields a characteristic
non-Gaussian velocity distribution. Another is the local virial (LV) relation,
the virial relation which holds even locally in collisionless systems through
phase mixing such as cold-collapse. A family of polytropes are examined from a
view point of these two characters. The LV relation imposes a strong constraint
on these models: only polytropes with index with a flat boundary
condition at the center are compatible with the numerical results, except for
the outer region. Using the analytic solutions based on the static and
spherical Jeans equation, we show that this incompatibility in the outer region
implies the important effect of anisotropy of velocity dispersion. Furthermore,
the velocity anisotropy is essential in explaining various numerical results
under the condition of the local virial relation.Comment: 8 pages, 5 figures, Proceedings of CN-Kyoto International Workshop on
Complexity and Nonextensivity; added a reference for section
Supporting the planning of a community fisheries monitoring and evaluation database: a collaborative project undertaken by CFDO, FLD, STREAM, VSO and AYAD
Cambodia is one of the poorest countries in the world; much of its population live in rural areas and many live below the local poverty line. The management of common property aquatic resources is of over-riding importance to food security and sustainable rural development in Cambodia. Aquatic resources are utilized principally by subsistence fishers and the landless, for whom aquatic resource use is an important livelihood activity.
Subsistence fishers access mainly the rivers, lakes and inundated forests in Tonle Sap provinces, the lower Mekong and Bassac regions and the upper part of the Mekong.
Freshwater capture fisheries probably contribute more to national food security and the national economy in Cambodia than in any other country in the world. (PDF contains 52 pages
Don Mendo de Acuña : episodio novelesco de la historia de Castilla
Copia Digital. España : Ministerio de Cultura y Deporte. Subdirección General de Coordinación Bibliotecaria, 2022- L
The tale of two centres
We study motion in the field of two fixed centres described by a family of
Einstein-dilaton-Maxwell theories. Transitions between regular and chaotic
motion are observed as the dilaton coupling is varied.Comment: 20 pages, RevTeX, 7 figures included, TeX format change
Chaos and Rotating Black Holes with Halos
The occurrence of chaos for test particles moving around a slowly rotating
black hole with a dipolar halo is studied using Poincar\'e sections. We find a
novel effect, particles with angular momentum opposite to the black hole
rotation have larger chaotic regions in phase space than particles initially
moving in the same direction.Comment: 9 pages, 4 Postscript figures. Phys. Rev. D, in pres
Chaos in Static Axisymmetric Spacetimes I : Vacuum Case
We study the motion of test particle in static axisymmetric vacuum spacetimes
and discuss two criteria for strong chaos to occur: (1) a local instability
measured by the Weyl curvature, and (2) a tangle of a homoclinic orbit, which
is closely related to an unstable periodic orbit in general relativity. We
analyze several static axisymmetric spacetimes and find that the first
criterion is a sufficient condition for chaos, at least qualitatively. Although
some test particles which do not satisfy the first criterion show chaotic
behavior in some spacetimes, these can be accounted for the second criterion.Comment: More comments for the quantitative estimation of chaos are added, and
some inappropriate terms are changed. This will appear on Class. Quant. Gra
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