4,016 research outputs found
Gravitational-wave bursts from the nuclei of distant galaxies and quasars: Proposal for detection using Doppler tracking of interplanetary spacecraft
Supermassive black holes which exist in the nuclei of many quasars and galaxies are examined along with the collapse which forms these holes and subsequent collisions between them which produce strong, broad-band bursts of gravitational waves. Such bursts might arrive at earth as often as 50 times per year--or as rarely as once each 300 years. The detection of such bursts with dual-frequency Doppler tracking of interplanetary spacecraft is considered
On the structure of line-driven winds near black holes
A general physical mechanism of the formation of line-driven winds at the
vicinity of strong gravitational field sources is investigated in the frame of
General Relativity. We argue that gravitational redshifting should be taken
into account to model such outflows. The generalization of the Sobolev
approximation in the frame of General Relativity is presented. We consider all
processes in the metric of a nonrotating (Schwarzschild) black hole. The
radiation force that is due to absorbtion of the radiation flux in lines is
derived. It is demonstrated that if gravitational redshifting is taken into
account, the radiation force becomes a function of the local velocity gradient
(as in the standard line-driven wind theory) and the gradient of . We
derive a general relativistic equation of motion describing such flow. A
solution of the equation of motion is obtained and confronted with that
obtained from the Castor, Abbott & Klein (CAK) theory. It is shown that the
proposed mechanism could have an important contribution to the formation of
line-driven outflows from compact objects.Comment: 20 pages, submitted to Ap
The geometry of a naked singularity created by standing waves near a Schwarzschild horizon, and its application to the binary black hole problem
The most promising way to compute the gravitational waves emitted by binary
black holes (BBHs) in their last dozen orbits, where post-Newtonian techniques
fail, is a quasistationary approximation introduced by Detweiler and being
pursued by Price and others. In this approximation the outgoing gravitational
waves at infinity and downgoing gravitational waves at the holes' horizons are
replaced by standing waves so as to guarantee that the spacetime has a helical
Killing vector field. Because the horizon generators will not, in general, be
tidally locked to the holes' orbital motion, the standing waves will destroy
the horizons, converting the black holes into naked singularities that resemble
black holes down to near the horizon radius. This paper uses a spherically
symmetric, scalar-field model problem to explore in detail the following BBH
issues: (i) The destruction of a horizon by the standing waves. (ii) The
accuracy with which the resulting naked singularity resembles a black hole.
(iii) The conversion of the standing-wave spacetime (with a destroyed horizon)
into a spacetime with downgoing waves by the addition of a ``radiation-reaction
field''. (iv) The accuracy with which the resulting downgoing waves agree with
the downgoing waves of a true black-hole spacetime (with horizon). The model
problem used to study these issues consists of a Schwarzschild black hole
endowed with spherical standing waves of a scalar field. It is found that the
spacetime metric of the singular, standing-wave spacetime, and its
radiation-reaction-field-constructed downgoing waves are quite close to those
for a Schwarzschild black hole with downgoing waves -- sufficiently close to
make the BBH quasistationary approximation look promising for
non-tidally-locked black holes.Comment: 12 pages, 6 figure
Schwarzschild black holes as unipolar inductors: expected electromagnetic power of a merger
(Abridged) The motion of a Schwarzschild black hole with velocity through a constant magnetic field in vacuum induces a
component of the electric field along the magnetic field, generating a non-zero
second Poincare electromagnetic invariant . This will
produce (e.g., via radiative effects and vacuum breakdown) an electric charge
density of the order of , where
is the Schwarzschild radius and is the mass of the black
hole; the charge density is similar to the Goldreich-Julian
density. The magnetospheres of moving black holes resemble in many respects the
magnetospheres of rotationally-powered pulsars, with pair formation fronts and
outer gaps, where the sign of the induced charge changes. As a result, the
black hole will generate bipolar electromagnetic jets each consisting of two
counter-aligned current flows (four current flows total), each carrying an
electric current of the order . The
electromagnetic power of the jets is ;
for a particular case of merging black holes the resulting Poynting power is , where is the radius of the orbit. In
addition, in limited regions near the horizon the first electromagnetic
invariant changes sign, so that the induced electric field becomes larger than
the magnetic field, . The total energy loss from a system of merging BHs
is a sum of two components with similar powers, one due to the rotation of
space-time within the orbit, driven by the non-zero angular momentum in the
system, and the other due to the linear motion of the BHs through the magnetic
field.Comment: Phys. Rev. D accepte
Shell sources as a probe of relativistic effects in neutron star models
A perturbing shell is introduced as a device for studying the excitation of
fluid motions in relativistic stellar models. We show that this approach allows
a reasonably clean separation of radiation from the shell and from fluid
motions in the star, and provides broad flexibility in the location and
timescale of perturbations driving the fluid motions. With this model we
compare the relativistic and Newtonian results for the generation of even
parity gravitational waves from constant density models. Our results suggest
that relativistic effects will not be important in computations of the
gravitational emission except possibly in the case of excitation of the neutron
star on very short time scales.Comment: 16 pages LaTeX with 6 eps figures; submitted to Phys. Rev.
Quantum variational measurement in the next generation gravitational-wave detectors
A relatively simple method of overcoming the Standard Quantum Limit in the
next-generation Advanced LIGO gravitational wave detector is considered. It is
based on the quantum variational measurement with a single short (a few tens of
meters) filter cavity. Estimates show that this method allows to reduce the
radiation pressure noise at low frequencies () to the level
comparable with or smaller than the low-frequency noises of non-quantum origin
(mirrors suspension noise, mirrors internal thermal noise, and gravity
gradients fluctuations).Comment: 12 pages, 4 figures; NSNS SNR estimates added; misprints correcte
Minimum Length from Quantum Mechanics and Classical General Relativity
We derive fundamental limits on measurements of position, arising from
quantum mechanics and classical general relativity. First, we show that any
primitive probe or target used in an experiment must be larger than the Planck
length, . This suggests a Planck-size {\it minimum ball} of uncertainty in
any measurement. Next, we study interferometers (such as LIGO) whose precision
is much finer than the size of any individual components and hence are not
obviously limited by the minimum ball. Nevertheless, we deduce a fundamental
limit on their accuracy of order . Our results imply a {\it device
independent} limit on possible position measurements.Comment: 8 pages, latex, to appear in the Physical Review Letter
Electromagnetic power of merging and collapsing compact objects
[Abridged] Electromagnetic emission can be produced as a precursor to the
merger, as a prompt emission during the collapse of a NS and at the spin-down
stage of the resulting BH. We demonstrate that the time evolution of the
axisymmetric force-free magnetic fields can be expressed in terms of the
hyperbolic Grad-Shafranov equation. We find exact non-linear time-dependent
split-monopole structure of magnetosphere driven by spinning and collapsing NS
in Schwarzschild geometry. Based on this solution, we argue that the collapse
of a NS into the BH happens smoothly, without natural formation of current
sheets or other dissipative structures on the open field lines and, thus, does
not allow the magnetic field to become disconnected from the star and escape to
infinity. Thus, as long as an isolated Kerr BH can produce plasma and currents,
it does not lose its open magnetic field lines, its magnetospheric structure
evolved towards a split monopole and the BH spins down electromagnetically. The
"no hair theorem", which assumes that the outside medium is a vacuum, is not
applicable in this case: highly conducting plasma introduces a topological
constraint forbidding the disconnection of the magnetic field lines from the
BH. Eventually, a single random large scale spontaneous reconnection event will
lead to magnetic field release, shutting down the electromagnetic BH engine
forever. We also discuss the nature of short Gamma Ray Bursts and suggest that
the similarity of the early afterglows properties of long and short GRBs can be
related to the fact that in both cases a spinning BH can retains magnetic field
for sufficiently long time to extract a large fraction of its rotation energy
and produce high energy emission via the internal dissipation in the wind
Holographic Entropy Packing inside a Black Hole
If general relativity is spontaneously induced, the black hole limit is
governed by a phase transition which occurs precisely at the would have been
horizon. The exterior Schwarzschild solution then connects with a novel core of
vanishing spatial volume. The Kruskal structure, admitting the exact Hawking
imaginary time periodicity, is recovered, with the conic defect defused at the
origin, rather than at the horizon. The entropy stored inside \textbf{any}
interior sphere is universal, equal to a quarter of its surface area, thus
locally saturating the 't Hooft-Susskind holographic bound. The associated
Komar mass and material energy functions are non-singular.Comment: [V3] accepted to PRL (version shortened, a paragraph on singularity
structure added); 10 pages, no figure
Speed Meter As a Quantum Nondemolition Measuring Device for Force
Quantum noise is an important issue for advanced LIGO. Although it is in
principle possible to beat the Standard Quantum Limit (SQL), no practical
recipe has been found yet. This paper dicusses quantum noise in the context of
speedmeter-a devise monitoring the speed of the testmass. The scheme proposed
to overcome SQL in this case might be more practical than the methods based on
monitoring position of the testmass.Comment: 7 pages of RevTex, 1 postscript figur
- …