2,951 research outputs found
Holography and non-locality in a closed vacuum-dominated universe
A closed vacuum-dominated Friedmann universe is asymptotic to a de Sitter
space with a cosmological event horizon for any observer. The holographic
principle says the area of the horizon in Planck units determines the number of
bits of information about the universe that will ever be available to any
observer. The wavefunction describing the probability distribution of mass
quanta associated with bits of information on the horizon is the boundary
condition for the wavefunction specifying the probability distribution of mass
quanta throughout the universe. Local interactions between mass quanta in the
universe cause quantum transitions in the wavefunction specifying the
distribution of mass throughout the universe, with instantaneous non-local
effects throughout the universe.Comment: 4 pages, no figures, to be published in Int. J. Theor. Phys,
references correcte
The Dynamics of General Relativity
This article--summarizing the authors' then novel formulation of General
Relativity--appeared as Chapter 7 of an often cited compendium edited by L.
Witten in 1962, which is now long out of print. Intentionally unretouched, this
posting is intended to provide contemporary accessibility to the flavor of the
original ideas. Some typographical corrections have been made: footnote and
page numbering have changed--but not section nor equation numbering etc. The
authors' current institutional affiliations are encoded in:
[email protected], [email protected], [email protected] .Comment: 30 pages (LaTeX2e), uses amsfonts, no figure
Excising das All: Evolving Maxwell waves beyond scri
We study the numerical propagation of waves through future null infinity in a
conformally compactified spacetime. We introduce an artificial cosmological
constant, which allows us some control over the causal structure near null
infinity. We exploit this freedom to ensure that all light cones are tilted
outward in a region near null infinity, which allows us to impose
excision-style boundary conditions in our finite difference code. In this
preliminary study we consider electromagnetic waves propagating in a static,
conformally compactified spacetime.Comment: 13 pages; incorporated material from gr-qc/051216
A covariant formalism of spin precession with respect to a reference congruence
We derive an effectively three-dimensional relativistic spin precession
formalism. The formalism is applicable to any spacetime where an arbitrary
timelike reference congruence of worldlines is specified. We employ what we
call a stopped spin vector which is the spin vector that we would get if we
momentarily make a pure boost of the spin vector to stop it relative to the
congruence. Starting from the Fermi transport equation for the standard spin
vector we derive a corresponding transport equation for the stopped spin
vector. Employing a spacetime transport equation for a vector along a
worldline, corresponding to spatial parallel transport with respect to the
congruence, we can write down a precession formula for a gyroscope relative to
the local spatial geometry defined by the congruence. This general approach has
already been pursued by Jantzen et. al. (see e.g. Jantzen, Carini and Bini,
Ann. Phys. 215 (1997) 1), but the algebraic form of our respective expressions
differ. We are also applying the formalism to a novel type of spatial parallel
transport introduced in Jonsson (Class. Quantum Grav. 23 (2006) 1), as well as
verifying the validity of the intuitive approach of a forthcoming paper
(Jonsson, Am. Journ. Phys. 75 (2007) 463) where gyroscope precession is
explained entirely as a double Thomas type of effect. We also present the
resulting formalism in explicit three-dimensional form (using the boldface
vector notation), and give examples of applications.Comment: 27 pages, 8 figure
Optical position meters analyzed in the non-inertial reference frames
In the framework of General Relativity we develop a method for analysis of
the operation of the optical position meters in their photodetectors proper
reference frames. These frames are non-inertial in general due to the action of
external fluctuative forces on meters test masses, including detectors. For
comparison we also perform the calculations in the laboratory (globally
inertial) reference frame and demonstrate that for certain optical schemes
laboratory-based analysis results in unmeasurable quantities, in contrast to
the detector-based analysis. We also calculate the response of the simplest
optical meters to weak plane gravitational waves and fluctuative motions of
their test masses. It is demonstrated that for the round-trip meter analysis in
both the transverse-traceless (TT) and local Lorentz (LL) gauges produces equal
results, while for the forward-trip meter corresponding results differ in
accordance with different physical assumptions (e.g. procedure of clocks
synchronization) implicitly underlying the construction of the TT and LL
gauges.Comment: 10 pages, 2 figures; co-author added, added section VC with
discussion of procedures of clocks synchronization, corrected sign in old
Eq.17 (currently it is Eq.18
Post-Newtonian Freely Specifiable Initial Data for Binary Black Holes in Numerical Relativity
Construction of astrophysically realistic initial data remains a central
problem when modelling the merger and eventual coalescence of binary black
holes in numerical relativity. The objective of this paper is to provide
astrophysically realistic freely specifiable initial data for binary black hole
systems in numerical relativity, which are in agreement with post-Newtonian
results. Following the approach taken by Blanchet, we propose a particular
solution to the time-asymmetric constraint equations, which represent a system
of two moving black holes, in the form of the standard conformal decomposition
of the spatial metric and the extrinsic curvature. The solution for the spatial
metric is given in symmetric tracefree form, as well as in Dirac coordinates.
We show that the solution differs from the usual post-Newtonian metric up to
the 2PN order by a coordinate transformation. In addition, the solutions,
defined at every point of space, differ at second post-Newtonian order from the
exact, conformally flat, Bowen-York solution of the constraints.Comment: 41 pages, no figures, accepted for publication in Phys. Rev. D,
significant revision in presentation (including added references and
corrected typos
Do academically gifted learners 7-11 in the Midwest School District achieve proportionate to their respective abilities?
Gifted children are special. Their potential, properly developed, is the clay from which teachers mold many of the leaders of tomorrow. In order for talented and gifted students to reach self-actualization the following_ elements must be present in their educational environment: 1. Early identification is vital. 2. Measurement of ability and achievement should be comprehensive and on-going. 3. Programs must be available to meet individual needs
Gravitational wave detectors based on matter wave interferometers (MIGO) are no better than laser interferometers (LIGO)
We show that a recent claim that matter wave interferometers have a much
higher sensitivity than laser interferometers for a comparable physical setup
is unfounded. We point out where the mistake in the earlier analysis is made.
We also disprove the claim that only a description based on the geodesic
deviation equation can produce the correct physical result. The equations for
the quantum dynamics of non-relativistic massive particles in a linearly
perturbed spacetime derived here are useful for treating a wider class of
related physical problems. A general discussion on the use of atom
interferometers for the detection of gravitational waves is also provided.Comment: 16 pages, REVTeX4; minor changes, one figure and a few references
were added, an additional appendix was included where we explain why,
contrary to the claims in gr-qc/0409099, the effects due to the reflection
off the mirrors cancel out in the final result for the phase shif
Hawking radiation in dispersive theories, the two regimes
We compute the black hole radiation spectrum in the presence of
high-frequency dispersion in a large set of situations. In all cases, the
spectrum diverges like the inverse of the Killing frequency. When studying the
low-frequency spectrum, we find only two regimes: an adiabatic one where the
corrections with respect to the standard temperature are small, and an abrupt
one regulated by dispersion, in which the near-horizon metric can be replaced
by step functions. The transition from one regime to the other is governed by a
single parameter which also governs the net redshift undergone by dispersive
modes. These results can be used to characterize the quasiparticles spectrum of
recent and future experiments aiming to detect the analogue Hawking radiation.
They also apply to theories of quantum gravity which violate Lorentz
invariance.Comment: 11 pages, 9 figure
Initial data for gravity coupled to scalar, electromagnetic and Yang-Mills fields
We give ansatze for solving classically the initial value constraints of
general relativity minimally coupled to a scalar field, electromagnetism or
Yang-Mills theory. The results include both time-symmetric and asymmetric data.
The time-asymmetric examples are used to test Penrose's cosmic censorship
inequality. We find that the inequality can be violated if only the weak energy
condition holds.Comment: 16 pages, RevTeX, references added, presentational changes, version
to appear in Phys Rev.
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