265 research outputs found
Scalar-Tensor Gravity Theory For Dynamical Light Velocity
A gravity theory is developed with the metric . In the present universe the
additional contribution from the scalar field in the metric
can generate an acceleration in the expansion of the universe, without negative
pressure and with a zero cosmological constant. In this theory, gravitational
waves will propagate at a different speed from non-gravitational waves. It is
suggested that gravitational wave experiments could test this observational
signature.Comment: 14 pages latex file. Additional material added. Accepted for
publication in Physics Letters
A scalar-tensor cosmological model with dynamical light velocity
The dynamical consequences of a bimetric scalar-tensor theory of gravity with
a dynamical light speed are investigated in a cosmological setting. The model
consists of a minimally-coupled self-gravitating scalar field coupled to
ordinary matter fields in the standard way through the metric:
\metric_{\mu\nu}+B\partial_\mu\phi\partial_\nu\phi. We show that in a
universe with matter that has a radiation-dominated equation of state, the
model allows solutions with a de Sitter phase that provides sufficient
inflation to solve the horizon and flatness problems. This behaviour is
achieved without the addition of a potential for the scalar field, and is shown
to be largely independent of its introduction. We therefore have a model that
is fundamentally different than the potential-dominated, slowly-rolling scalar
field of the standard models inflationary cosmology. The speed of gravitational
wave propagation is predicted to be significantly different from the speed of
matter waves and photon propagation in the early universe.Comment: 12 pages, uses amsart and amssymb. Minor corrections, to appear in
Phys. Lett.
Comments on "Note on varying speed of light theories"
In a recent note Ellis criticizes varying speed of light theories on the
grounds of a number of foundational issues. His reflections provide us with an
opportunity to clarify some fundamental matters pertaining to these theories
Black holes in the varying speed of light theory
We consider the effect of the \emph{Varying Speed of Light} theory on
non-rotating black holes. We show that in any varying- theory, the
Schwarzschild solution is neither static nor stationary. For a no-charged black
hole, the singularity in the Schwarzschild horizon cannot be removed by
coordinate transformation. Hence, no matter can enter the horizon, and the
interior part of the black hole is separated from the rest of the Universe. If
, then the size of the Schwarzschild radius increases with time. The
higher value of the speed of light in the very early Universe may have caused a
large reduction in the probability of the creation of the primordial black
holes and their population.The same analogy is also considered for the charged
black holes.Comment: 5 page
Noncommutative Quantum Gravity
The possible role of gravity in a noncommutative geometry is investigated.
Due to the Moyal *-product of fields in noncommutative geometry, it is
necessary to complexify the metric tensor of gravity. We first consider the
possibility of a complex Hermitian, nonsymmetric and discuss the
problems associated with such a theory. We then introduce a complex symmetric
(non-Hermitian) metric, with the associated complex connection and curvature,
as the basis of a noncommutative spacetime geometry. The spacetime coordinates
are in general complex and the group of local gauge transformations is
associated with the complex group of Lorentz transformations CSO(3,1). A real
action is chosen to obtain a consistent set of field equations. A Weyl
quantization of the metric associated with the algebra of noncommuting
coordinates is employed.Comment: 13 pages LaTex. Changes to text and new text added. To be published
in Physics Letters
The Role of Radioactivities in Astrophysics
I present both a history of radioactivity in astrophysics and an introduction
to the major applications of radioactive abundances to astronomy
A time-space varying speed of light and the Hubble Law in static Universe
We consider a hypothetical possibility of the variability of light velocity
with time and position in space which is derived from two natural postulates.
For the consistent consideration of such variability we generalize
translational transformations of the Theory of Relativity. The formulae of
transformations between two rest observers within one inertial system are
obtained. It is shown that equality of velocities of two particles is as
relative a statement as simultaneity of two events is. We obtain the expression
for the redshift of radiation of a rest source which formally reproduces the
Hubble Law. Possible experimental implications of the theory are discussed.Comment: 7 page
Dynamical System Approach to Cosmological Models with a Varying Speed of Light
Methods of dynamical systems have been used to study homogeneous and
isotropic cosmological models with a varying speed of light (VSL). We propose
two methods of reduction of dynamics to the form of planar Hamiltonian
dynamical systems for models with a time dependent equation of state. The
solutions are analyzed on two-dimensional phase space in the variables where is a function of a scale factor . Then we show how the
horizon problem may be solved on some evolutional paths. It is shown that the
models with negative curvature overcome the horizon and flatness problems. The
presented method of reduction can be adopted to the analysis of dynamics of the
universe with the general form of the equation of state .
This is demonstrated using as an example the dynamics of VSL models filled with
a non-interacting fluid. We demonstrate a new type of evolution near the
initial singularity caused by a varying speed of light. The singularity-free
oscillating universes are also admitted for positive cosmological constant. We
consider a quantum VSL FRW closed model with radiation and show that the
highest tunnelling rate occurs for a constant velocity of light if and . It is also proved that the considered class of
models is structurally unstable for the case of .Comment: 18 pages, 5 figures, RevTeX4; final version to appear in PR
Variable-Speed-of-Light Cosmology from Brane World Scenario
We argue that the four-dimensional universe on the TeV brane of the
Randall-Sundrum scenario takes the bimetric structure of Clayton and Moffat,
with gravitons traveling faster than photons instead, while the radion varies
with time. We show that such brane world bimetric model can thereby solve the
flatness and the cosmological constant problems, provided the speed of a
graviton decreases to the present day value rapidly enough. The resolution of
other cosmological problems such as the horizon problem and the monopole
problem requires supplementation by inflation, which may be achieved by the
radion field provided the radion potential satisfies the slow-roll
approximation.Comment: 18 pages, LaTeX, revised version to appear in Phys. Rev.
Automatic regularization by quantization in reducible representations of CCR: Point-form quantum optics with classical sources
Electromagnetic fields are quantized in manifestly covariant way by means of
a class of reducible representations of CCR. transforms as a Hermitian
four-vector field in Minkowski four-position space (no change of gauge), but in
momentum space it splits into spin-1 massless photons (optics) and two massless
scalars (similar to dark matter). Unitary dynamics is given by point-form
interaction picture, with minimal-coupling Hamiltonian constructed from fields
that are free on the null-cone boundary of the Milne universe. SL(2,C)
transformations and dynamics are represented unitarily in positive-norm Hilbert
space describing four-dimensional oscillators. Vacuum is a Bose-Einstein
condensate of the -oscillator gas. Both the form of and its
transformation properties are determined by an analogue of the twistor
equation. The same equation guarantees that the subspace of vacuum states is,
as a whole, Poincar\'e invariant. The formalism is tested on quantum fields
produced by pointlike classical sources. Photon statistics is well defined even
for pointlike charges, with UV/IR regularizations occurring automatically as a
consequence of the formalism. The probabilities are not Poissonian but of a
R\'enyi type with . The average number of photons occurring in
Bremsstrahlung splits into two parts: The one due to acceleration, and the one
that remains nonzero even if motion is inertial. Classical Maxwell
electrodynamics is reconstructed from coherent-state averaged solutions of
Heisenberg equations. Static pointlike charges polarize vacuum and produce
effective charge densities and fields whose form is sensitive to both the
choice of representation of CCR and the corresponding vacuum state.Comment: 2 eps figures; in v2 notation in Eq. (39) and above Eq. (38) is
correcte
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