1,118 research outputs found
The metaphysics of Machian frame-dragging
The paper investigates the kind of dependence relation that best portrays Machian frame-dragging in general relativity. The question is tricky because frame-dragging relates local inertial frames to distant distributions of matter in a time-independent way, thus establishing some sort of non-local link between the two. For this reason, a plain causal interpretation of frame-dragging faces huge challenges. The paper will shed light on the issue by using a generalized structural equation model analysis in terms of manipulationist counterfactuals recently applied in the context of metaphysical enquiry by Schaffer (2016) and Wilson (2017). The verdict of the analysis will be that frame-dragging is best understood in terms of a novel type of dependence relation that is half-way between causation and grounding
Estimates of the total gravitation radiation in the head-on black hole collision
We report on calculations of the total gravitational energy radiated in the
head-on black hole collision, where we use the geometry of the
Robinson-Trautman metrics.Comment: 10 pages, 2 figures, LaTeX2
Vacuum effects in an asymptotically uniformly accelerated frame with a constant magnetic field
In the present article we solve the Dirac-Pauli and Klein Gordon equations in
an asymptotically uniformly accelerated frame when a constant magnetic field is
present. We compute, via the Bogoliubov coefficients, the density of scalar and
spin 1/2 particles created. We discuss the role played by the magnetic field
and the thermal character of the spectrum.Comment: 17 pages. RevTe
Thermodynamics of (3+1)-dimensional black holes with toroidal or higher genus horizons
We examine counterparts of the Reissner-Nordstrom-anti-de Sitter black hole
spacetimes in which the two-sphere has been replaced by a surface Sigma of
constant negative or zero curvature. When horizons exist, the spacetimes are
black holes with an asymptotically locally anti-de Sitter infinity, but the
infinity topology differs from that in the asymptotically Minkowski case, and
the horizon topology is not S^2. Maximal analytic extensions of the solutions
are given. The local Hawking temperature is found. When Sigma is closed, we
derive the first law of thermodynamics using a Brown-York type quasilocal
energy at a finite boundary, and we identify the entropy as one quarter of the
horizon area, independent of the horizon topology. The heat capacities with
constant charge and constant electrostatic potential are shown to be positive
definite. With the boundary pushed to infinity, we consider thermodynamical
ensembles that fix the renormalized temperature and either the charge or the
electrostatic potential at infinity. Both ensembles turn out to be
thermodynamically stable, and dominated by a unique classical solution.Comment: 25 pages, REVTeX v3.1, contains 5 LaTeX figures. (Typos corrected,
references and minor comments added. To be published in Phys. Rev. D.
Head-on collisions of black holes: the particle limit
We compute gravitational radiation waveforms, spectra and energies for a
point particle of mass falling from rest at radius into a
Schwarzschild hole of mass . This radiation is found to lowest order in
with the use of a Laplace transform. In contrast with numerical
relativity results for head-on collisions of equal-mass holes, the radiated
energy is found not to be a monotonically increasing function of initial
separation; there is a local radiated-energy maximum at . The
present results, along with results for infall from infinity, provide a
complete catalog of waveforms and spectra for particle infall. We give a
representative sample from that catalog and an interesting observation: Unlike
the simple spectra for other head-on collisions (either of particle and hole,
or of equal mass holes) the spectra for show a series of
evenly spaced bumps. A simple explanation is given for this. Lastly, our energy
vs. results are compared with approximation methods used elsewhere, for
small and for large initial separation.Comment: 15 pages, REVTeX, 25 figure
Regularization of Linear Ill-posed Problems by the Augmented Lagrangian Method and Variational Inequalities
We study the application of the Augmented Lagrangian Method to the solution
of linear ill-posed problems. Previously, linear convergence rates with respect
to the Bregman distance have been derived under the classical assumption of a
standard source condition. Using the method of variational inequalities, we
extend these results in this paper to convergence rates of lower order, both
for the case of an a priori parameter choice and an a posteriori choice based
on Morozov's discrepancy principle. In addition, our approach allows the
derivation of convergence rates with respect to distance measures different
from the Bregman distance. As a particular application, we consider sparsity
promoting regularization, where we derive a range of convergence rates with
respect to the norm under the assumption of restricted injectivity in
conjunction with generalized source conditions of H\"older type
On the energy of homogeneous cosmologies
An energy for the homogeneous cosmological models is presented. More
specifically, using an appropriate natural prescription, we find the energy
within any region with any gravitational source for a large class of gravity
theories--namely those with a tetrad description--for all 9 Bianchi types. Our
energy is given by the value of the Hamiltonian with homogeneous boundary
conditions; this value vanishes for all regions in all Bianchi class A models,
and it does not vanish for any class B model. This is so not only for
Einstein's general relativity but, moreover, for the whole 3-parameter class of
tetrad-teleparallel theories. For the physically favored one parameter
subclass, which includes the teleparallel equivalent of Einstein's theory as an
important special case, the energy for all class B models is, contrary to
expectation, negative.Comment: 11 pages, reformated with minor change
Safety, pharmacokinetics, and pharmacodynamic properties of oral DEBIO1143 (AT-406) in patients with advanced cancer: results of a first-in-man study
Spin, gravity, and inertia
The gravitational effects in the relativistic quantum mechanics are
investigated. The exact Foldy-Wouthuysen transformation is constructed for the
Dirac particle coupled to the static spacetime metric. As a direct application,
we analyze the non-relativistic limit of the theory. The new term describing
the specific spin (gravitational moment) interaction effect is recovered in the
Hamiltonian. The comparison of the true gravitational coupling with the purely
inertial case demonstrates that the spin relativistic effects do not violate
the equivalence principle for the Dirac fermions.Comment: Revtex, 12 pages, no figures, accepted in Phys. Rev. Let
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