12,064 research outputs found
On the gravitomagnetic effects in cylindrically symmetric spacetimes
Using gyroscopes we generalize results, obtained for the gravitomagnetic
clock effect in the particular case when the exterior spacetime is produced by
a rotating dust cylinder, to the case when the vacuum spacetime is described by
the general cylindrically symmetric Lewis spacetime. Results are contrasted
with those obtained for the Kerr spacetime.Comment: 11 pages Latex, to appear in J.Math.Phy
Shear-free and homology conditions for self-gravitating dissipative fluids
The shear free condition is studied for dissipative relativistic
self-gravitating fluids in the quasi-static approximation. It is shown that, in
the Newtonian limit, such condition implies the linear homology law for the
velocity of a fluid element, only if homology conditions are further imposed on
the temperature and the emission rate. It is also shown that the shear-free
plus the homogeneous expansion rate conditions are equivalent (in the Newtonian
limit) to the homology conditions. Deviations from homology and their
prospective applications to some astrophysical scenarios are discussed, and a
model is worked out.Comment: 13 pages Latex. To apppear in Month.Not.Roy.Astr.Soc. Corrected typo
Cylindrical Collapse and Gravitational Waves
We study the matching conditions for a collapsing anisotropic cylindrical
perfect fluid, and we show that its radial pressure is non zero on the surface
of the cylinder and proportional to the time dependent part of the field
produced by the collapsing fluid. This result resembles the one that arises for
the radiation - though non-gravitational - in the spherically symmetric
collapsing dissipative fluid, in the diffusion approximation.Comment: Some comments and a new reference added. To appear in Class. Quantum.
Gra
Geodesics in Lewis Spacetime
The geodesic equations are integrated for the Lewis metric and the effects of
the different parameters appearing in the Weyl class on the motion of test
particles are brought out. Particular attention deserves the appearance of a
force parallel to the axial axis and without Newtonian analogue.Comment: 15 pages, Late
Dedollarization, Indexation and Nominalization: The Chilean Experience
This paper revisits the Chilean experience with dollarization, indexation and nominalization in the 1958-2003 period. The purpose is to understand how Chile generally avoided dollarization and actually dedollarized in the 80s in order to draw some lessons for other countries. We find that many policies that Chile pursued are not easy to implement elsewhere. Some key characteristics of the Chilean process are related to initial institutional conditions and developments, whereas others are connected to macroeconomic performance and specific regulations. Indexation plays a key role in explaining how dollarization can be avoided.
The Levi-Civita spacetime as a limiting case of the Gamma spacetime
It is shown that the Levi-Civita metric can be obtained from a family of the
Weyl metric, the Gamma metric, by taking the limit when the length of its
Newtonian image source tends to infinity. In this process a relationship
appears between two fundamental parameters of both metrics.Comment: LaTeX2e 17 page
Matrix Ernst Potentials and Orthogonal Symmetry for Heterotic String in Three Dimensions
A new matrix representation for low-energy limit of heterotic string theory
reduced to three dimensions is considered. The pair of matrix Ernst Potentials
uniquely connected with the coset matrix is derived. The action of the symmetry
group on the Ernst potentials is established.Comment: 10 pages in LaTe
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