9,369 research outputs found
Importance of Granular Structure in the Initial Conditions for the Elliptic Flow
We show effects of granular structure of the initial conditions (IC) of
hydrodynamic description of high-energy nucleus-nucleus collisions on some
observables, especially on the elliptic-flow parameter v2. Such a structure
enhances production of isotropically distributed high-pT particles, making v2
smaller there. Also, it reduces v2 in the forward and backward regions where
the global matter density is smaller, so where such effects become more
efficacious.Comment: 4 pages, 5 figure
Rotation intrinsic spin coupling--the parallelism description
For the Dirac particle in the rotational system, the rotation induced inertia
effect is analogously treated as the modification of the "spin connection" on
the Dirac equation in the flat spacetime, which is determined by the equivalent
tetrad. From the point of view of parallelism description of spacetime, the
obtained torsion axial-vector is just the rotational angular velocity, which is
included in the "spin connection". Furthermore the axial-vector spin coupling
induced spin precession is just the rotation-spin(1/2) interaction predicted by
Mashhoon. Our derivation treatment is straightforward and simplified in the
geometrical meaning and physical conception, however the obtained conclusions
are consistent with that of the other previous work.Comment: 10 pages, no figur
Renormalization of the N=1 Abelian Super-Chern-Simons Theory Coupled to Parity-Preserving Matter
We analyse the renormalizability of an Abelian N=1 super-Chern-Simons model
coupled to parity-preserving matter on the light of the regularization
independent algebraic method. The model shows to be stable under radiative
corrections and to be gauge anomaly free.Comment: Latex, 7 pages, no figure
The Teleparallel Lagrangian and Hamilton-Jacobi Formalism
We analyze the Teleparallel Equivalent of General Relativity (TEGR) from the
point of view of Hamilton-Jacobi approach for singular systemsComment: 11 pages, no figures, to appear in GR
On Spin-driven inflation from fields in General Relativity and COBE data
Obukhov spin-driven inflation in General Relativity is extended to include
inflaton fields.A de Sitter phase solution is obtained and new slow-rolling
conditions for the spin potential are obtained.The spin potential reduces to
Obukhov result at the present epoch of the Universe where the spin density is
low with comparison to the Early Universe spin densities.A relation betwenn the
spin density energy and the temperature fluctuation can be obtained which allow
us to determine the spin density energy in terms of the COBE data for
temperature fluctuations.Comment: Latex file 8K
Dirac spinor fields in the teleparallel gravity: comment on "Metric-affine approach to teleparallel gravity"
We show that the coupling of a Dirac spinor field with the gravitational
field in the teleparallel equivalent of general relativity is consistent. For
an arbitrary SO(3,1) connection there are two possibilities for the coupling of
the spinor field with the gravitational field. The problems of consistency
raised by Y. N. Obukhov and J. G. Pereira in the paper {\it Metric-affine
approach to teleparallel gravity} [gr-qc/0212080] take place only in the
framework of one particular coupling. By adopting an alternative coupling the
consistency problem disappears.Comment: 8 pages, Latex file, no figures, to appear in the Phys. Rev. D as a
Commen
Torsion Gravity: a Reappraisal
The role played by torsion in gravitation is critically reviewed. After a
description of the problems and controversies involving the physics of torsion,
a comprehensive presentation of the teleparallel equivalent of general
relativity is made. According to this theory, curvature and torsion are
alternative ways of describing the gravitational field, and consequently
related to the same degrees of freedom of gravity. However, more general
gravity theories, like for example Einstein-Cartan and gauge theories for the
Poincare and the affine groups, consider curvature and torsion as representing
independent degrees of freedom. By using an active version of the strong
equivalence principle, a possible solution to this conceptual question is
reviewed. This solution favors ultimately the teleparallel point of view, and
consequently the completeness of general relativity. A discussion of the
consequences for gravitation is presented.Comment: RevTeX, 34 pages. Review article to be published by Int. J. Mod.
Phys.
Riemannian and Teleparallel Descriptions of the Scalar Field Gravitational Interaction
A comparative study between the metric and the teleparallel descriptions of
gravitation is made for the case of a scalar field. In contrast to the current
belief that only spin matter could detect the teleparallel geometry, scalar
matter being able to feel the metric geometry only, we show that a scalar field
is able not only to feel anyone of these geometries, but also to produce
torsion. Furthermore, both descriptions are found to be completely equivalent,
which means that in fact, besides coupling to curvature, a scalar field couples
also to torsion.Comment: Minor corrections made, and a paragraph added to the last section.
Version to appear in Gen. Rel. Gra
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