60 research outputs found
Conservative, gravitational self-force for a particle in circular orbit around a Schwarzschild black hole in a Radiation Gauge
This is the second of two companion papers on computing the self-force in a
radiation gauge; more precisely, the method uses a radiation gauge for the
radiative part of the metric perturbation, together with an arbitrarily chosen
gauge for the parts of the perturbation associated with changes in black-hole
mass and spin and with a shift in the center of mass. We compute the
conservative part of the self-force for a particle in circular orbit around a
Schwarzschild black hole. The gauge vector relating our radiation gauge to a
Lorenz gauge is helically symmetric, implying that the quantity h_{\alpha\beta}
u^\alpha u^\beta (= h_{uu}) must have the same value for our radiation gauge as
for a Lorenz gauge; and we confirm this numerically to one part in 10^{13}. As
outlined in the first paper, the perturbed metric is constructed from a Hertz
potential that is in term obtained algebraically from the the retarded
perturbed spin-2 Weyl scalar, \psi_0 . We use a mode-sum renormalization and
find the renormalization coefficients by matching a series in L = \ell + 1/2 to
the large-L behavior of the expression for the self-force in terms of the
retarded field h_{\alpha\beta}^{ret}; we similarly find the leading
renormalization coefficients of h_{uu} and the related change in the angular
velocity of the particle due to its self-force. We show numerically that the
singular part of the self-force has the form f_{\alpha} \propto < \nabla_\alpha
\rho^{-1}>, the part of \nabla_\alpha \rho^{-1} that is axisymmetric about a
radial line through the particle. This differs only by a constant from its form
for a Lorenz gauge. It is because we do not use a radiation gauge to describe
the change in black-hole mass that the singular part of the self-force has no
singularity along a radial line through the particle and, at least in this
example, is spherically symmetric to subleading order in \rho.Comment: 21 pages, 2 figure
EMRI corrections to the angular velocity and redshift factor of a mass in circular orbit about a Kerr black hole
This is the first of two papers on computing the self-force in a radiation
gauge for a particle moving in circular, equatorial orbit about a Kerr black
hole. In the EMRI (extreme-mass-ratio inspiral) framework, with mode-sum
renormalization, we compute the renormalized value of the quantity
, gauge-invariant under gauge transformations
generated by a helically symmetric gauge vector; and we find the related order
correction to the particle's angular velocity at fixed renormalized
redshift (and to its redshift at fixed angular velocity). The radiative part of
the perturbed metric is constructed from the Hertz potential which is extracted
from the Weyl scalar by an algebraic inversion\cite{sf2}. We then write the
spin-weighted spheroidal harmonics as a sum over spin-weighted spherical
harmonics and use mode-sum renormalization to find the renormalization
coefficients by matching a series in to the large- behavior of
the expression for . The
non-radiative parts of the perturbed metric associated with changes in mass and
angular momentum are calculated in the Kerr gauge
“The Fans of Michael Jackson v Wade Robson and James Safechuck”: Forensic Fandom and the Staging of a Media Tribunal
This essay analyses fan reactions to the sexual abuse allegations brought forward against Michael Jackson in Leaving Neverland (Dan Reed, 2019). In particular, it focuses on fans’ production of nonfiction media produced in defense of Jackson, trying to restore the artist’s reputation by discrediting his accusers. Based on textual and content analysis of videos by The Michael Jackson Innocent Project (MJIP) and its wider network, this essay positions these videos within the context of documentaries and nonfiction programs produced on the singer. Arguing that the videos represent a form of “forensic fandom,” the essay maintains that fans stage a “media tribunal” against Jackson’s accusers to defend the singer. Because of their biased argumentation, however, fans reinforce myths about disingenuous allegations of sexual violence
Towards Context-Aware Adaptable Web Services.
ABSTRACT In this paper, we present a context framework that facilitates the development and deployment of context-aware adaptable Web services. Web services are provided with context information about clients that may be utilized to provide a personalized behavior. Context is extensible with new types of information at any time without any changes to the underlying infrastructure. Context processing is done by Web services, context plugins, or context services. Context plugins and context services pre-and post-process Web service messages based on the available context information. Both are essential for automatic context processing and automatic adaption of Web services to new context types without the necessity to adjust the Web services themselves. We implemented the context framework within the ServiceGlobe system, our open and distributed Web service platform
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