59 research outputs found
Tachyonic Quintessential Inflation
We study the possibility to construct an observationally viable scenario
where both early Inflation and the recently detected accelerated expansion of
the universe can be explained by using a single scalar field associated with
the Tachyon. The Reheating phase becomes crucial to enable us to have a
consistent cosmology and also to get a second accelerated expansion period. A
discussion using an exponential potential is presented.Comment: 5 pages, Revtex4. Added some references. To be published in Physical
Review
Dark energy and Dark matter interaction in light of the second law of thermodynamics
In the context of thermodynamics we discuss the way inevitable emerge an
interaction between dark components, and in this way, provide a mechanism to
understand the limits of the LCDM model and the class of interaction models
between dark components. Using observational data we have tested two models of
explicit interaction between dark components and reconstructed the evolution of
temperatures for both components. We found that observations suggest the
interaction exist with energy flowing from dark energy to dark matter. The best
fit also suggest a phantom equation of state parameter for dark energy. We
discuss the results having in mind the constraints imposed by thermodynamics.Comment: 18 pages, 4 figure
A fractal LTB model cannot explain Dark Energy
We revisited the problem of describing, on average, a fractal distribution of
matter using a Lemaitre-Tolman-Bondi (LTB) solution. Here we study the fractal
structure of our local universe having a fractal dimension and a scale
transition. We test our model with the latest type Ia supernova data, the
Pantheon compilation, and discuss problems and possible improvements for it,
concluding that a fractal transition in LTB cosmology cannot be used to explain
the effects of dark energy but it can be useful to study structures at low
scales
Emulating dark energy models with known equation of state via the created cold dark matter scenario
In this work we establish only at background dynamics level, the equivalence
between the Created Cold Dark Matter (CCDM) model and diverse dark energy (DE)
models. We find that for a barotropic or linear equation of state (EoS) for the
DE, , and standard matter sector the corresponding CCDM model is
described by the same functional structure of the ratio of particle production,
. For a different EoS the functional form of the term is not
longer maintained, however, in the case of a polytropic EoS given by the
Chaplygin gas the resulting term can be written as the one obtained in
the barotropic case under certain considerations.Comment: 7 pages, no figures. Published version in Physics of the Dark
Univers
Matter production effects and interacting scenario within a reconstructed mimetic cosmology for late times
In this work we explore two possible scenarios that can be considered to
extend a recent proposed model by the authors known as reconstructed mimetic
cosmology. This study is complemented with an statistical analysis for each
case. The first scenario considers the inclusion of matter production as a
possible source of cosmic expansion in the reconstructed mimetic model, at
effective level was found that this construction can cross the phantom divide,
the model evolves from quintessence to phantom dark energy. The second scenario
corresponds to a construction of an interacting scheme for the dark sector
which is described by the unified mimetic model. The resulting interaction term
(not imposed by an Ansatz), , exhibits changes of sign leading to the
violation of the second law along the cosmic evolution and non adiabaticity;
the temperatures for the components of the dark sector are computed and such
components are shown to be out of thermal equilibrium.Comment: 24 pages, 8 figures, references added. Accepted for publication in
EPJ
R^2-corrections to Chaotic Inflation
Scalar density cosmological perturbations, spectral indices and reheating in
a chaotic inflationary universe model, in which a higher derivative term is
added, are investigated. This term is supposed to play an important role in the
early evolution of the Universe, specifically at times closer to the Planck
era.Comment: 14 pages, accepted for publication in MPL
Inflation as a response to protect the Holographic Principle
A model where the inflationary phase emerges as a response to protect the
Fischler-Susskind holographic bound is described. A two fluid model in a closed
universe inflation picture is assumed, and a discussion on conditions under
which is possible to obtain an additional exponential expansion phase as those
currently observed is given.Comment: 6 pages, 2 figures. Accepted for publication in MPL
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