5 research outputs found
Effects of Pair Creation on Charged Gravitational Collapse
We investigate the effects of pair creation on the internal geometry of a
black hole, which forms during the gravitational collapse of a charged massless
scalar field. Classically, strong central Schwarzschild-like singularity forms,
and a null, weak, mass-inflation singularity arises along the Cauchy horizon,
in such a collapse. We consider here the discharge, due to pair creation, below
the event horizon and its influence on the {\it dynamical formation} of the
Cauchy horizon. Within the framework of a simple model we are able to trace
numerically the collapse. We find that a part of the Cauchy horizon is replaced
by the strong space-like central singularity. This fraction depends on the
value of the critical electric field, , for the pair creation.Comment: LaTex, 27 pages, including 14 figures. Some points are clarified,
typos corrected. Version accepted for publication in Phys.Rev.
Formation and Evaporation of Charged Black Holes
We investigate the dynamical formation and evaporation of a spherically
symmetric charged black hole. We study the self-consistent one loop order
semiclassical back-reaction problem. To this end the mass-evaporation is
modeled by an expectation value of the stress-energy tensor of a neutral
massless scalar field, while the charge is not radiated away. We observe the
formation of an initially non extremal black hole which tends toward the
extremal black hole , emitting Hawking radiation. If also the discharge
due to the instability of vacuum to pair creation in strong electric fields
occurs, then the black hole discharges and evaporates simultaneously and decays
regularly until the scale where the semiclassical approximation breaks down. We
calculate the rates of the mass and the charge loss and estimate the life-time
of the decaying black holes.Comment: 23 pages, 7 eps figures, RevTex, accepted for publication in Phys.
Rev.
Computing gravitational waves from slightly nonspherical stellar collapse to black hole: Odd-parity perturbation
Nonspherical stellar collapse to a black hole is one of the most promising
gravitational wave sources for gravitational wave detectors. We numerically
study gravitational waves from a slightly nonspherical stellar collapse to a
black hole in linearized Einstein theory. We adopt a spherically collapsing
star as the zeroth-order solution and gravitational waves are computed using
perturbation theory on the spherical background. In this paper we focus on the
perturbation of odd-parity modes. Using the polytropic equations of state with
polytropic indices and 3, we qualitatively study gravitational waves
emitted during the collapse of neutron stars and supermassive stars to black
holes from a marginally stable equilibrium configuration. Since the matter
perturbation profiles can be chosen arbitrarily, we provide a few types for
them. For , the gravitational waveforms are mainly characterized by a
black hole quasinormal mode ringing, irrespective of perturbation profiles
given initially. However, for , the waveforms depend strongly on the
initial perturbation profiles. In other words, the gravitational waveforms
strongly depend on the stellar configuration and, in turn, on the ad hoc choice
of the functional form of the perturbation in the case of supermassive stars.Comment: 31 pages, accepted for publication in Phys. Rev. D, typos and minor
errors correcte