6,220 research outputs found
Pseudoclassical model for Weyl particle in 10 dimensions
A pseudoclassical model to describe Weyl particle in 10 dimensions is
proposed. In course of quantization both the massless Dirac equation and the
Weyl condition are reproduced automatically. The construction can be relevant
to Ramond-Neveu-Schwarz strings where the Weyl reduction in the Ramond sector
has to be made by hand.Comment: 5 page
On Useful Conformal Tranformations In General Relativity
Local conformal transformations are known as a useful tool in various
applications of the gravitational theory, especially in cosmology. We describe
some new aspects of these transformations, in particular using them for
derivation of Einstein equations for the cosmological and Schwarzschild
metrics. Furthermore, the conformal transformation is applied for the
dimensional reduction of the Gauss-Bonnet topological invariant in to the
spaces of lower dimensions.Comment: 17 pages, LaTeX. The paper is intended mainly for pedagogical
purposes and represents a collection of exercises concerning local conformal
transformations and dimensional reduction. To be published in "Gravitation
and Cosmology
Dynamo in the Intra-Cluster Medium: Simulation of CGL-MHD Turbulent Dynamo
The standard magnetohydrodynamic (MHD) description of the plasma in the hot,
magnetized gas of the intra-cluster (ICM) medium is not adequate because it is
weakly collisional. In such collisionless magnetized gas, the microscopic
velocity distribution of the particles is not isotropic, giving rise to kinetic
effects on the dynamical scales. These kinetic effects could be important in
understanding the turbulence, as so as the amplification and maintenance of the
magnetic fields in the ICM. It is possible to formulate fluid models for
collisonless or weakly collisional gas by introducing modifications in the MHD
equations. These models are often referred as kinetic MHD (KMHD). Using a KMHD
model based on the CGL-closure, which allows the adiabatic evolution of the two
components of the pressure tensor (the parallel and perpendicular components
with respect to the local magnetic field), we performed 3D numerical
simulations of forced turbulence in order to study the amplification of an
initially weak seed magnetic field. We found that the growth rate of the
magnetic energy is comparable to that of the ordinary MHD turbulent dynamo, but
the magnetic energy saturates in a level smaller than of the MHD case. We also
found that a necessary condition for the dynamo works is to impose limits to
the anisotropy of the pressure.Comment: 3 pages, 1 figure, 274 IAU Symposium: Advances in Plasma Astrophysic
Análise de tendências de temperatura mÃnima do Brasil.
A concentração dos gases de efeito estufa vem aumentando consideravelmente nos últimos 150 anos e tem sido considerado como principal causa do aquecimento global no planeta nesse perÃodo. O objetivo do trabalho foi analisar as tendências de temperatura mÃnima nas cinco regiões do Brasil. Foram calculadas as temperaturas mÃnimas mensais e anuais de cada estação por meio da média aritmética dos valores diários e mensais, respectivamente. Calculou-se também a média móvel de cinco anos e o desvio da temperatura mÃnima em relação a média da temperatura mÃnima no perÃodo de estudo de cada estação meteorológica. As análises dos desvios da temperatura mÃnima anual, em relação à média da série de dados de cada estação meteorológica analisada, indicaram tendências de aumento significativo nas cinco regiões do paÃs.CBA 2009
- …