18,849 research outputs found
Relativistic gravitational collapse in comoving coordinates: The post-quasistatic approximation
A general iterative method proposed some years ago for the description of
relativistic collapse, is presented here in comoving coordinates. For doing
that we redefine the basic concepts required for the implementation of the
method for comoving coordinates. In particular the definition of the
post-quasistatic approximation in comoving coordinates is given. We write the
field equations, the boundary conditions and a set of ordinary differential
equations (the surface equations) which play a fundamental role in the
algorithm. As an illustration of the method, we show how to build up a model
inspired in the well known Schwarzschild interior solution. Both, the adiabatic
and non adiabatic, cases are considered.Comment: 14 pages, 11 figures; updated version to appear in Int. J. Modern
Phys.
Collapsing Spheres Satisfying An "Euclidean Condition"
We study the general properties of fluid spheres satisfying the heuristic
assumption that their areas and proper radius are equal (the Euclidean
condition). Dissipative and non-dissipative models are considered. In the
latter case, all models are necessarily geodesic and a subclass of the
Lemaitre-Tolman-Bondi solution is obtained. In the dissipative case solutions
are non-geodesic and are characterized by the fact that all non-gravitational
forces acting on any fluid element produces a radial three-acceleration
independent on its inertial mass.Comment: 1o pages, Latex. Title changed and text shortened to fit the version
to appear in Gen.Rel.Grav
On the Critical Behaviour of Heat Conducting Sphere out of Hydrostatic Equilibrium
We comment further on the behaviour of a heat conducting fluid when a
characteristic parameter of the system approaches a critical value.Comment: 4 pages, emTex (LaTex 2.09), submitted to Classical and Quantum
Gravity (Comments and Addenda
On the dual interpretation of zero-curvature Friedmann-Robertson-Walker models
Two possible interpretations of FRW cosmologies (perfect fluid or dissipative
fluid)are considered as consecutive phases of the system. Necessary conditions
are found, for the transition from perfect fluid to dissipative regime to
occur, bringing out the conspicuous role played by a particular state of the
system (the ''critical point '').Comment: 13 pages Latex, to appear in Class.Quantum Gra
Dynamics of Viscous Dissipative Plane Symmetric Gravitational Collapse
We present dynamical description of gravitational collapse in view of Misner
and Sharp's formalism. Matter under consideration is a complicated fluid
consistent with plane symmetry which we assume to undergo dissipation in the
form of heat flow, radiation, shear and bulk viscosity. Junction conditions are
studied for a general spacetime in the interior and Vaidya spacetime in the
exterior regions. Dynamical equations are obtained and coupled with causal
transport equations derived in context of Mller Israel Stewart
theory. The role of dissipative quantities over collapse is investigated.Comment: 17 pages, accepted for publication in Gen. Relativ. Gra
Dissipative fluids out of hydrostatic equilibrium
In the context of the M\"{u}ller-Israel-Stewart second order phenomenological
theory for dissipative fluids, we analyze the effects of thermal conduction and
viscosity in a relativistic fluid, just after its departure from hydrostatic
equilibrium, on a time scale of the order of relaxation times. Stability and
causality conditions are contrasted with conditions for which the ''effective
inertial mass'' vanishes.Comment: 21 pages, 1 postscript figure (LaTex 2.09 and epsfig.sty required)
Submitted to Classical and Quantum Gravit
Why does gravitational radiation produce vorticity?
We calculate the vorticity of world--lines of observers at rest in a
Bondi--Sachs frame, produced by gravitational radiation, in a general Sachs
metric. We claim that such an effect is related to the super--Poynting vector,
in a similar way as the existence of the electromagnetic Poynting vector is
related to the vorticity in stationary electrovacum spacetimes.Comment: 9 pages; to appear in Classical and Quantum Gravit
Charged Cylindrical Collapse of Anisotropic Fluid
Following the scheme developed by Misner and Sharp, we discuss the dynamics
of gravitational collapse. For this purpose, an interior cylindrically
symmetric spacetime is matched to an exterior charged static cylindrically
symmetric spacetime using the Darmois matching conditions. Dynamical equations
are obtained with matter dissipating in the form of shear viscosity. The effect
of charge and dissipative quantities over the cylindrical collapse are studied.
Finally, we show that homogeneity in energy density and conformal flatness of
spacetime are necessary and sufficient for each other.Comment: 19 pages, accepted for publication in Gen. Relativ. Gra
- …