1,646 research outputs found
Gravitational waves during inflation from a 5D large-scale repulsive gravity model
We investigate, in the transverse traceless (TT) gauge, the generation of the
relic background of gravitational waves, generated during an early inflationary
stage, on the framework of a large-scale repulsive gravity model. We calculate
the spectrum of the tensor metric fluctuations of an effective 4D
Schwarzschild-de-Sitter metric, which is obtained after implementing a planar
coordinate transformation on a 5D Ricci-flat metric solution, in the context of
a non-compact Kaluza-Klein theory of gravity. We found that the spectrum is
nearly scale invariant under certain conditions. One interesting aspect of this
model is that is possible to derive dynamical field equations for the tensor
metric fluctuations, valid not just at cosmological scales, but also at
astrophysical scales, from the same theoretical model. The astrophysical and
cosmological scales are determined by the gravity- antigravity radius, which is
a natural length scale of the model, that indicates when gravity becomes
repulsive in nature.Comment: Improved version, accepted in Physics Letters
Inflation from the bang of a white hole induced from a 6D vacuum state
Using ideas of STM theory, but starting from a 6D vacuum state, we propose an
inflationary model where the universe emerges from the blast of a white hole.
Under this approach, the expansion is affected by a geometrical deformation
induced by the gravitational attraction of the hole, which should be
responsible for the k_{R}-non invariant spectrum of galaxies (and likewise of
the matter density) today observed.Comment: 9 pages, 1 figure Accepted for publication in Physics Letters
Primordial SdS universe from a 5D vacuum: scalar field fluctuations on Schwarzschild and Hubble horizons
We study scalar field fluctuations of the inflaton field in an early
inflationary universe on an effective 4D Schwarzschild-de Sitter (SdS) metric,
which is obtained after make a planar coordinate transformation on a 5D
Ricci-flat Schwarzschild-de Sitter (SdS) static metric. We obtain the important
result that the spectrum of fluctuations at zeroth order is independent of the
scalar field mass on Schwarzschild scales, while on cosmological scales it
exhibits a mass dependence. However, in the first-order expansion, the spectrum
depends of the inflaton mass and the amplitude is linear with the Black-Hole
(BH) mass .Comment: Final version to be published in JCA
Noncompact KK theory of gravity: stochastic treatment for a nonperturbative inflaton field in a de Sitter expansion
We study a stochastic formalism for a nonperturbative treatment of the
inflaton field in the framework of a noncompact Kaluza-Klein (KK) theory during
an inflationary (de Sitter) expansion, without the slow-roll approximation.Comment: version to be published in Phys. Lett.
The primordial explosion of a false white hole from a 5D vacuum
We explore the cosmological consequences of some possible big bang produced
by a black-hole with mass in an 5D extended SdS. Under these particular
circumstances, the effective 4D metric obtained by the use of a constant
foliation on the extra coordinate is comported as a false white-hole (FWH),
which evaporates for all unstable modes that have wavelengths bigger than the
size of the FWH. Outside the white hole the repulsive gravitational field can
be considered as weak, so that the dynamics for fluctuations of the inflaton
field and the scalar perturbations of the metric can be linearized.Comment: Final version to be published in PLB. arXiv admin note: substantial
text overlap with arXiv:1304.698
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