141 research outputs found
Semiclassical corrections to the Einstein equation and Induced Matter Theory
The induced Einstein equation on a perturbed brane in the Induced Matter
Theory is re-analyzed. We indicate that in a conformally flat background, the
local quantum corrections to the Einstein equation can be obtained via the IMT.
Using the FRW metric as the 4D gravitational model, we show that the classical
fluctuations of the brane may be related to the quantum corrections to the
classical Einstein equation. In other words, the induced Einstein equation on
the perturbed brane correspond with the semiclassical Einstein equation.Comment: 9 pages, to appear in GR
Covariant extrinsic gravity and the geometric origin of dark energy
We construct the covariant or model independent induced Einstein-Yang-Mills
field equations on a 4-dimensional brane embedded isometrically in an
D-dimensional bulk space, assuming the matter fields are confined to the brane.
Applying this formalism to cosmology, we derive the generalized Friedmann
equations. We derive the density parameter of dark energy in terms of width of
the brane, normal curvature radii and the number of extra large dimensions. We
show that dark energy could actually be the manifestation of the local
extrinsic shape of the brane. It is shown that the predictions of this model
are in good agreement with observation if we consider an 11-dimensional bulk
space.Comment: 29 pages, 2 figures, revised versio
Quantum Hamilton-Jacobi cosmology and classical-quantum correlation
How the time evolution which is typical for classical cosmology emerges from
quantum cosmology? The answer is not trivial because the Wheeler-DeWitt
equation is time independent. A framework associating the quantum
Hamilton-Jacobi to the minisuperspace cosmological models has been introduced
in [1]. In this paper, we show that time dependence and quantum-classical
correspondence both arise naturally in the quantum Hamilton-Jacobi formalism of
quantum mechanics applied to quantum cosmology. We study the quantum
Hamilton-Jacobi cosmology of spatially flat homogeneous and isotropic early
universe whose matter content is a perfect fluid. The classical cosmology
emerge around one Planck time where its linear size is around a few millimeter,
without needing any classical inflationary phase afterwards to make it grow to
its present size.Comment: 10 pages, to appear in IJT
Holography from quantum cosmology
The Weyl-Wigner-Groenewold-Moyal formalism of deformation quantization is
applied to the closed Friedmann-Lema\^itre-Robertson-Walker (FLRW) cosmological
model. We show that the phase space average for the surface of the apparent
horizon is quantized in units of the Planck's surface, and that the total
entropy of the universe is also quantized. Taking into account these two
concepts, it is shown that 't Hooft conjecture on the cosmological holographic
principle (CHP) in radiation and dust dominated quantum universes is satisfied
as a manifestation of quantization. This suggests that the entire universe (not
only inside the apparent horizon) can be seen as a two-dimensional information
structure encoded on the apparent horizon.Comment: 7 pages, 1 figure, to appear in Phys. Rev.
Why the measured cosmological constant is small
In a quest to explain the small value of the today's cosmological constant,
following the approach introduced in [1], we show that the theoretical value of
cosmological constant is consistent with its observational value. In more
detail, we study the Freidmann-Lama\^{\i}tre-Robertson-Walker cosmology
embedded isometrically in an -dimensional ambient space. The field
equations determines in terms of other measurable fundamental
constants. Specifically, it predicts that the cosmological constant measured
today be , as observed.Comment: 7 pages, 1 figures, to appear in Physics of Dark Univers
One-loop quantum cosmological correction to the gravitational constant in the closed Friedmann-Robertson-Walker universe
In this paper, we calculate the one-loop quantum cosmological corrections to
the kink energy in the closed Friedmann-Robertson-Walker universe in which the
fluctuation potential has a shape invariance property. We
use the generalized zeta function regularization method to implement our setup
for describing quantum kink-like states. It is conjectured that the corrections
lead to the renormalized gravitational constant
Five dimensional cosmological traversable wormhole
In this paper, a traversable wormhole in the
Friedmann-Lema\^{\i}tre-Robertson-Walker (FLRW) model with one extra spacelike
compact dimension is studied. We have chosen dynamical compactification as the
evolution of the fifth dimension. In this respect, we study how the existence
of the extra dimension, affect the behavior of the energy density, the shape
function and the scale factor. It is shown that the total matter can be
non-exotic and the violation of the weak energy condition can be avoided.Comment: 11 pages, 1 figure, to appear in Annals of Physic
Unification of Higgs and Maxwell fields in Brane-Kaluza-Klein gravity
The unification of Higgs and electromagnetic fields in the context of higher
dimensional gravity is studied. We show that these fields arise from an extra
large dimension together with a compact small dimension. The question of the
localization of the gauge fields and their relation to junction conditions is
also addressed.Comment: 9 pages, no figures, minor change
Dirac observables and boundary proposals in quantum cosmology
We study the reduced phase space quantization of a closed Friedmann Universe,
where matter content is constituted by two (no-interacting) fluids, namely dust
(or cold dark matter) and radiation. It is shown that, for this particular
model, specific boundary conditions can be related to the algebra of Dirac
observables.Comment: 6 pages, no figures, to appear in Phys. Rev.
Schr\"odinger-Wheeler-DeWitt equation in chaplygin gas FRW cosmological model
We present a chaplygin gas Friedmann-Robertson-Walker quantum cosmological
model. In this work the Schutz's variational formalism is applied with
positive, negative, and zero constant spatial curvature. In this approach the
notion of time can be recovered. These give rise to
Schr\"odinger-Wheeler-DeWitt equation for the scale factor. We use the
eigenfunctions in order to construct wave packets for each case. We study the
time dependent behavior of the expectation value of the scale factor, using the
many-worlds interpretations of quantum mechanics.Comment: 11 pages, 1 figure, to appear in IJT
- …