395 research outputs found
Gravitational energy of a magnetized Schwarzschild black hole - a teleparallel approach
We investigate the distribution of gravitational energy on the spacetime of a
Schwarzschild black hole immersed in a cosmic magnetic field. This is done in
the context of the {\it Teleparallel Equivalent of General Relativity}, which
is an alternative geometrical formulation of General Relativity, where gravity
is describe by a spacetime endowed with torsion, rather than curvature, with
the fundamental field variables being tetrads. We calculate the energy enclosed
by a two-surface of constant radius - in particular, the energy enclosed by the
event horizon of the black hole. In this case we find that the magnetic field
has the effect of increasing the gravitational energy as compared to the vacuum
Schwarzschild case. We also compute the energy (i) in the weak magnetic field
limit, (ii) in the limit of vanishing magnetic field, and (iii) in the absence
of the black hole. In all cases our results are consistent with what should be
expected on physical grounds.Comment: version to match the one to be published on General Relativity and
Gravitatio
Gravitational Radiation from Post-Newtonian Sources and Inspiralling Compact Binaries
The article reviews the current status of a theoretical approach to the
problem of the emission of gravitational waves by isolated systems in the
context of general relativity. Part A of the article deals with general
post-Newtonian sources. The exterior field of the source is investigated by
means of a combination of analytic post-Minkowskian and multipolar
approximations. The physical observables in the far-zone of the source are
described by a specific set of radiative multipole moments. By matching the
exterior solution to the metric of the post-Newtonian source in the near-zone
we obtain the explicit expressions of the source multipole moments. The
relationships between the radiative and source moments involve many non-linear
multipole interactions, among them those associated with the tails (and
tails-of-tails) of gravitational waves. Part B of the article is devoted to the
application to compact binary systems. We present the equations of binary
motion, and the associated Lagrangian and Hamiltonian, at the third
post-Newtonian (3PN) order beyond the Newtonian acceleration. The
gravitational-wave energy flux, taking consistently into account the
relativistic corrections in the binary moments as well as the various tail
effects, is derived through 3.5PN order with respect to the quadrupole
formalism. The binary's orbital phase, whose prior knowledge is crucial for
searching and analyzing the signals from inspiralling compact binaries, is
deduced from an energy balance argument.Comment: 109 pages, 1 figure; this version is an update of the Living Review
article originally published in 2002; available on-line at
http://www.livingreviews.org
Search for high-mass resonances decaying to dilepton final states in pp collisions at sâ=7 TeV with the ATLAS detector
The ATLAS detector at the Large Hadron Collider is used to search for high-mass resonances decaying to an electron-positron pair or a muon-antimuon pair. The search is sensitive to heavy neutral ZâČ gauge bosons, Randall-Sundrum gravitons, Z * bosons, techni-mesons, Kaluza-Klein Z/Îł bosons, and bosons predicted by Torsion models. Results are presented based on an analysis of pp collisions at a center-of-mass energy of 7 TeV corresponding to an integrated luminosity of 4.9 fbâ1 in the e + e â channel and 5.0 fbâ1 in the ÎŒ + ÎŒ âchannel. A Z âČ boson with Standard Model-like couplings is excluded at 95 % confidence level for masses below 2.22 TeV. A Randall-Sundrum graviton with coupling k/MPl=0.1 is excluded at 95 % confidence level for masses below 2.16 TeV. Limits on the other models are also presented, including Technicolor and Minimal ZâČ Models
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