674 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
The effects of a monetary expansion on the euro zone economy
Economic and Monetary Unión is a big endeavor leading towards the integration of European Unión economies. It involves the coordination of economic and fiscal policies, a common monetay policy and a common currency, the Euro. From the 28 member states of the European Unión (EU hereinafter), 19 of them have reached a higher degree of integration and have adopted the euro. The current económic crisis that started in 2007 has led the European Central BAnk (ECB) to apply non-standard measures like quantitative easing (QE) to avoid deflation and increase output in the euro área. This work explains the non-standard measures tha have been applied in the euro área until now. It also estimates an autoregressive vector (VAR) to quantify the expected effects of QE on production, prices, interest rates and Exchange rates in the euro area.Facultad de Ciencias de la EmpresaUniversidad Politécnica de Cartagen
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
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
Universal Non-Gaussian Velocity Distribution in Violent Gravitational Processes
We study the velocity distribution in spherical collapses and cluster-pair
collisions by use of N-body simulations. Reflecting the violent gravitational
processes, the velocity distribution of the resultant quasi-stationary state
generally becomes non-Gaussian. Through the strong mixing of the violent
process, there appears a universal non-Gaussian velocity distribution, which is
a democratic (equal-weighted) superposition of many Gaussian distributions (DT
distribution). This is deeply related with the local virial equilibrium and the
linear mass-temperature relation which characterize the system. We show the
robustness of this distribution function against various initial conditions
which leads to the violent gravitational process. The DT distribution has a
positive correlation with the energy fluctuation of the system. On the other
hand, the coherent motion such as the radial motion in the spherical collapse
and the rotation with the angular momentum suppress the appearance of the DT
distribution.Comment: 11 pages, 19 eps figures, RevTex, submitted to PRE, Revised version,
minor change
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