618 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
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
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
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.
Super exponential inflation from a dynamical foliation of a 5D vacuum state
We introduce super exponential inflation () from a 5D
Riemann-flat canonical metric on which we make a dynamical foliation. The
resulting metric describes a super accelerated expansion for the early universe
well-known as super exponential inflation that, for very large times, tends to
an asymptotic de Sitter (vacuum dominated) expansion. The scalar field
fluctuations are analyzed. The important result here obtained is that the
spectral index for energy density fluctuations is not scale invariant, and for
cosmological scales becomes . However, for astrophysical
scales this spectrum changes to negative values .Comment: Final version, to be published in Phys. Lett.
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