1,443 research outputs found
Conformal Properties of an Evaporating Black Hole Model
We use a new, conformally-invariant method of analysis to test incomplete
null geodesics approaching the singularity in a model of an evaporating black
hole for the possibility of extensions of the conformal metric. In general, a
local conformal extension is possible from the future but not from the past
Zero temperature black holes in semiclassical gravity
The semiclassical Einstein equations are solved to first order in for the case of an extreme or nearly extreme Reissner-Nordstr\"{o}m
black hole perturbed by the vacuum stress-energy of quantized free fields. It
is shown that, for realistic fields of spin 0, 1/2, or 1, any zero temperature
black hole solution to the equations must have an event horizon at ,
with the charge of the black hole. It is further shown that no black hole
solutions with can be obtained by solving the semiclassical
Einstein equations perturbatively.Comment: 7 pages, to appear in the Proceedings of the Ninth Marcel Grossmann
Meeting, change in titl
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
Low Frequency Gravitational Waves from White Dwarf MACHO Binaries
The possibility that Galactic halo MACHOs are white dwarfs has recently
attracted much attention. Using the known properties of white dwarf binaries in
the Galactic disk as a model, we estimate the possible contribution of halo
white dwarf binaries to the low-frequency (10^{-5} Hz} < f < 10^{-1}Hz)
gravitational wave background. Assuming the fraction of white dwarfs in
binaries is the same in the halo as in the disk, we find the confusion
background from halo white dwarf binaries could be five times stronger than the
expected contribution from Galactic disk binaries, dominating the response of
the proposed space based interferometer LISA. Low-frequency gravitational wave
observations will be the key to discovering the nature of the dark MACHO binary
population.Comment: 9 pages, 1 figure, AASTe
Effects of quantized fields on the spacetime geometries of static spherically symmetric black holes
Analytic approximations for the stress-energy of quantized fields in the
Hartle-Hawking state in static black hole spacetimes predict divergences on the
event horizon of the black hole for a number of important cases. Such
divergences, if real, could substantially alter the spacetime geometry near the
event horizon, possibly preventing the black hole from existing. The results of
three investigations of these types of effects are presented. The first
involves a new analytic approximation for conformally invariant fields in
Reissner-Nordstrom spacetimes which is finite on the horizon. The second
focuses on the stress-energy of massless scalar fields in Schwarzschild-de
Sitter black holes. The third focuses on the stress-energy of massless scalar
fields in zero temperature black hole geometries that could be solutions to the
semiclassical backreaction equations near the event horizon of the black hole.Comment: 5 pages. To appear in the "Proceedings of the Eleventh Marcel
Grossmann Meeting on General Relativity", July 2006, Berlin, German
Renormalization of the charged scalar field in curved space
The DeWitt-Schwinger proper time point-splitting procedure is applied to a
massive complex scalar field with arbitrary curvature coupling interacting with
a classical electromagnetic field in a general curved spacetime. The scalar
field current is found to have a linear divergence. The presence of the
external background gauge field is found to modify the stress-energy tensor
results of Christensen for the neutral scalar field by adding terms of the form
to the logarithmic counterterms. These results are shown to be
expected from an analysis of the degree of divergence of scalar quantum
electrodynamics.Comment: 24 pages REVTe
An Analytic Model with Critical Behavior in Black Hole Formation
A simple analytic model is presented which exhibits a critical behavior in
black hole formation, namely, collapse of a thin shell coupled with outgoing
null fluid. It is seen that the critical behavior is caused by the
gravitational nonlinearity near the event horizon. We calculate the value of
the critical exponent analytically and find that it is very dependent on the
coupling constants of the system.Comment: 21pp., ReVTeX, 7 figures (postscript, compressed and uuencoded),
TIT/HEP-266/COSMO-4
Consensus approach to discrepancies arising from independent double reading of screening mammograms
- âŠ