608 research outputs found
Double-slit interference pattern from single-slit screen and its gravitational analogues
The double slit experiment (DSE) is known as an important cornerstone in the
foundations of physical theories such as Quantum Mechanics and Special
Relativity. A large number of different variants of it were designed and
performed over the years. We perform and discuss here a new verion with the
somewhat unexpected results of obtaining interference pattern from single-slit
screen. This outcome, which shows that the routes of the photons through the
array were changed, leads one to discuss it, using the equivalence principle,
in terms of geodesics mechanics. We show using either the Brill's version of
the canonical formulation of general relativity or the linearized version of it
that one may find corresponding and analogous situations in the framework of
general relativity.Comment: 51 pages, 12 Figures five of them contain two subfigures and thus the
number of figures is 17, 1 Table. Some minor changes introduced, especially,
in the reference
Vector Theory of Gravity
We proposed a gravitation theory based on an analogy with electrodynamics on
the basis of a vector field. For the first time, to calculate the basic
gravitational effects in the framework of a vector theory of gravity, we use a
Lagrangian written with gravitational radiation neglected and generalized to
the case of ultra-relativistic speeds. This allows us to accurately calculate
the values of all three major gravity experiments: the values of the perihelion
shift of Mercury, the light deflection angle in the gravity field of the Sun
and the value of radar echo delay. The calculated values coincide with the
observed ones. It is shown that, in this theory, there exists a model of an
expanding Universe.Comment: 9 page
Refining Vision Videos
[Context and motivation] Complex software-based systems involve several
stakeholders, their activities and interactions with the system. Vision videos
are used during the early phases of a project to complement textual
representations. They visualize previously abstract visions of the product and
its use. By creating, elaborating, and discussing vision videos, stakeholders
and developers gain an improved shared understanding of how those abstract
visions could translate into concrete scenarios and requirements to which
individuals can relate. [Question/problem] In this paper, we investigate two
aspects of refining vision videos: (1) Refining the vision by providing
alternative answers to previously open issues about the system to be built. (2)
A refined understanding of the camera perspective in vision videos. The impact
of using a subjective (or "ego") perspective is compared to the usual
third-person perspective. [Methodology] We use shopping in rural areas as a
real-world application domain for refining vision videos. Both aspects of
refining vision videos were investigated in an experiment with 20 participants.
[Contribution] Subjects made a significant number of additional contributions
when they had received not only video or text but also both - even with very
short text and short video clips. Subjective video elements were rated as
positive. However, there was no significant preference for either subjective or
non-subjective videos in general.Comment: 15 pages, 25th International Working Conference on Requirements
Engineering: Foundation for Software Quality 201
Gravitational collapse in 2+1 dimensional AdS spacetime
We present results of numerical simulations of the formation of black holes
from the gravitational collapse of a massless, minimally-coupled scalar field
in 2+1 dimensional, axially-symmetric, anti de-Sitter (AdS) spacetime. The
geometry exterior to the event horizon approaches the BTZ solution, showing no
evidence of scalar `hair'. To study the interior structure we implement a
variant of black-hole excision, which we call singularity excision. We find
that interior to the event horizon a strong, spacelike curvature singularity
develops. We study the critical behavior at the threshold of black hole
formation, and find a continuously self-similar solution and corresponding
mass-scaling exponent of approximately 1.2. The critical solution is universal
to within a phase that is related to the angle deficit of the spacetime.Comment: 31 pages, 20 figures, LaTeX. Replaced with version to be published in
Phys. Rev.
On the Back Reaction Problem for Gravitational Perturbations
We derive the effective energy-momentum tensor for cosmological perturbations
and prove its gauge-invariance. The result is applied to study the influence of
perturbations on the behaviour of the Friedmann background in inflationary
Universe scenarios. We found that the back reaction of cosmological
perturbations on the background can become important already at energies below
the self-reproduction scale.Comment: 4 pages, uses LATE
A Decade of Multiwavelength Observations of the TeV Blazar 1ES 1215+303: Extreme Shift of the Synchrotron Peak Frequency and Long-term Optical-Gamma-Ray Flux Increase
Blazars are known for their variability on a wide range of timescales at all wavelengths. Most studies of TeV gamma-ray blazars focus on short timescales, especially during flares. With a decade of observations from the Fermi-LAT and VERITAS, we present an extensive study of the long-term multiwavelength radio-to-gamma-ray flux-density variability, with the addition of a couple of short-time radio-structure and optical polarization observations of the blazar 1ES 1215+303 (z = 0.130), with a focus on its gamma-ray emission from 100 MeV to 30 TeV. Multiple strong GeV gamma-ray flares, a long-term increase in the gamma-ray and optical flux baseline, and a linear correlation between these two bands are observed over the ten-year period. Typical HBL behaviors are identified in the radio morphology and broadband spectrum of the source. Three stationary features in the innermost jet are resolved by Very Long Baseline Array at 43.1, 22.2, and 15.3 GHz. We employ a two-component synchrotron self-Compton model to describe different flux states of the source, including the epoch during which an extreme shift in energy of the synchrotron peak frequency from infrared to soft X-rays is observed
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
Analysis of Kaon Production at SIS Energies
We analyse the production and propagation of pions and kaons in heavy-ion
reactions from 0.8 -- 1.8~AGeV within a coupled channel transport
approach including the kaon production channels and . Assuming the hyperon selfenergy to be 2/3 of the nucleon selfenergy
we find that all inclusive experimental spectra at SIS energies can be
reproduced reasonably well without any selfenergies for the kaons although a
slightly repulsive kaon potential cannot be excluded by the present data on
kaon spectra and flow.Comment: 19 pages, LaTeX, including 8 postscript figures, to appear in Nucl.
Phys.
The structure of the extreme Schwarzschild-de Sitter space-time
The extreme Schwarzschild-de Sitter space-time is a spherically symmetric
solution of Einstein's equations with a cosmological constant Lambda and mass
parameter m>0 which is characterized by the condition that 9 Lambda m^2=1. The
global structure of this space-time is here analyzed in detail. Conformal and
embedding diagrams are constructed, and synchronous coordinates which are
suitable for a discussion of the cosmic no-hair conjecture are presented. The
permitted geodesic motions are also analyzed. By a careful investigation of the
geodesics and the equations of geodesic deviation, it is shown that specific
families of observers escape from falling into the singularity and approach
nonsingular asymptotic regions which are represented by special "points" in the
complete conformal diagram. The redshift of signals emitted by particles which
fall into the singularity, as detected by those observers which escape, is also
calculated.Comment: 19 pages, 10 figures, LaTeX, to appear in Gen. Rel. Gra
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