arXiv subjects

M. C. Bento

Publications and source records attributed to M. C. Bento.

At least 19 recordsLinked to original sources

arXiv2009

Coupling dark energy with Standard Model states

In this contribution one examines the coupling of dark energy to the gauge fields, to neutrinos, and to the Higgs field. In the first case, one shows how a putative evolution of the fundamental couplings of strong and weak interactions via coupling to dark energy through a generalized Bekenstein-type model may cause deviations on the statistical nuclear decay Rutherford-Soddy law. Existing bounds for the weak interaction exclude any significant deviation. For neutrinos, a perturbative approach is developed which allows for considering viable varying mass neutrino models coupled to any quintessence-type field. The generalized Chaplygin model is considered as an example. For the coupling with the Higgs field one obtains an interesting cosmological solution which includes the unification of dark energy and dark matter.

hep-ph↗

arXiv2009

Dark energy and the Rutherford-Soddy radiative decay law

It is shown that a putative evolution of the fundamental couplings of strong and weak interactions via coupling to dark energy through a generalized Bekenstein-type model may, for a linear model of variation, cause deviations on the statistical nuclear decay Rutherford-Soddy law unless bounds are imposed on the parameters of this variation. Existing bounds for the weak interaction exclude any significant deviation. Bounds on the strong interaction are much less stringent.

astro-ph.CO↗

arXiv2008

The variation of the electromagnetic coupling and quintessence

The properties of quintessence are examined through the study of the variation of the electromagnetic coupling. We consider two simple quintessence models with a modified exponential potential and study the parameter space constraints derived from the existing observational bounds on the variation of the fine structure constant and the most recent Wilkinson Microwave Anisotropy Probe observations.

astro-ph↗

arXiv2008

A Simple Quintessence Model

A simple model of quintessential inflation with the modified exponential potential $e^{-αϕ} [A+(ϕ-ϕ_0)^2]$ is analyzed in the braneworld context. Considering reheating via instant preheating, we conclude that the model exhibits transient acceleration at late times for $0.96 \lesssim A α^2 \lesssim 1.26$ and $271 \lesssim ϕ_0 α\lesssim 273$, while permanent acceleration is obtained for $2.3\times10^{-8} \lesssim A α^2 \lesssim 0.98$ and $255 \lesssim ϕ_0 α\lesssim 273$. The steep parameter $α$ is constrained to be in the range $5.3 \lesssim α\lesssim 10.8$.

astro-ph↗

arXiv2008

Brane assisted quintessential inflation with transient acceleration

A simple model of quintessential inflation with the modified exponential potential exp(-αϕ) [A + (ϕ-ϕ_0)^2] is analyzed in the braneworld context. Considering reheating via instant preheating, it is shown that the evolution of the scalar field ϕfrom inflation to the present epoch is consistent with the observational constraints in a wide region of the parameter space. The model exhibits transient acceleration at late times for 0.96 < A α^2 < 1.26 and 271 < ϕ_0 α< 273, while permanent acceleration is obtained for 2.3 10^{-8} < A α^2 < 0.98 and 255 < ϕ_0 α< 273. The steep parameter αis constrained to be in the range 5.3 < α< 10.8.

astro-ph↗

arXiv2006

The electromagnetic coupling and the dark side of the Universe

We examine the properties of dark energy and dark matter through the study of the variation of the electromagnetic coupling. For concreteness, we consider the unification model of dark energy and dark matter, the generalized Chaplygin gas model (GCG), characterized by the equation of state $p=-\frac{A}{ρ^α}$, where $p$ is the pressure, $ρ$ is the energy density and $A$ and $α$ are positive constants. The coupling of electromagnetism with the GCG's scalar field can give rise to such a variation. We compare our results with experimental data, and find that the degeneracy on parameters $α$ and $A_s$, $A_s \equiv A / ρ_{ch0}^{1+α}$, is considerable.

astro-ph↗

arXiv2006

Braneworld inflation from an effective field theory after WMAP three-year data

In light of the results from the WMAP three-year sky survey, we study an inflationary model based on a single-field polynomial potential, with up to quartic terms in the inflaton field. Our analysis is performed in the context of the Randall-Sundrum II braneworld theory, and we consider both the high-energy and low-energy (i.e. the standard cosmology case) limits of the theory. We examine the parameter space of the model, which leads to both large-field and small-field inflationary type solutions. We conclude that small field inflation, for a potential with a negative mass square term, is in general favored by current bounds on the tensor-to-scalar perturbation ratio rs.

astro-ph↗

arXiv2006

Observational constraints on modified gravity models and the Poincaré dodecahedral topology

We study the constraints that spatial topology may place on the parameters of models that account for the accelerated expansion of the universe via infrared modifications to general relativity, namely the Dvali-Gabadadze-Porrati braneworld model as well as the Dvali-Turner and Cardassian models. By considering the Poincaré dodecahedral space as the circles-in-the-sky observable spatial topology, we examine the constraints that can be placed on the parameters of each model using type Ia supernovae data together with the baryon acoustic peak in the large scale correlation function of the Sloan Digital Sky Survey of luminous red galaxies and the Cosmic Microwave Background Radiation shift parameter data. We show that knowledge of spatial topology does provide relevant constraints, particularly on the curvature parameter, for all models.

astro-ph↗

arXiv2006

Generalized Chaplygin gas model, supernovae and cosmic topology

In this work we study to which extent the knowledge of spatial topology may place constraints on the parameters of the generalized Chaplygin gas (GCG) model for unification of dark energy and dark matter. By using both the Poincaré dodecahedral and binary octahedral spaces as the observable spatial topologies, we examine the current type Ia supernovae (SNe Ia) constraints on the GCG model parameters. We show that the knowledge of spatial topology does provide additional constraints on the $A_s$ parameter of the GCG model but does not lift the degeneracy of the $α$ parameter.

gr-qc↗

arXiv2006

Braneworld cosmology: sneutrino inflation and leptogenesis

Modifications to the Friedmann equation in brane cosmology can have important implications for early universe phenomena such as inflation and the generation of the baryon asymmetry. In the framework of braneworld cosmology, we discuss a mechanism for baryogenesis via leptogenesis in the supersymmetric context, where the sneutrino is responsible for both inflation and the generation of the baryon asymmetry in the universe.

hep-ph↗

arXiv2005

Aspects of thermal leptogenesis in braneworld cosmology

The mechanism of thermal leptogenesis is investigated in the high-energy regime of braneworld cosmology. Within the simplest seesaw framework with hierarchical heavy Majorana neutrinos, we study the implications of the modified Friedmann equation on the realization of this mechanism. In contrast with the usual leptogenesis scenario of standard cosmology, where low-energy neutrino data favors a mildly strong washout regime, we find that leptogenesis in the braneworld regime is successfully realized in a weak washout regime. Furthermore, a quasi-degenerate light neutrino mass spectrum is found to be compatible with this scenario. For an initially vanishing heavy Majorana neutrino abundance, thermal leptogenesis in the brane requires the decaying heavy Majorana neutrino mass to be M1 > 10^10 GeV and the fundamental five-dimensional gravity scale 10^12 < M5 < 10^16 GeV, which corresponds to a transition from brane to standard cosmology at temperatures 10^8 < Tt < 10^14 GeV.

hep-ph↗

arXiv2005

Supernovae constraints on dark energy and modified gravity models

We use the Type Ia Supernova gold sample to constrain the parameters of dark energy models namely the Cardassian, Dvali-Turner (DT) and generalized Chaplygin gas (GCG) models. In our best fit analysis for these dark energy proposals we consider flat and the non-flat priors. For all models, we find that relaxing the flatness condition implies that data favors a positive curvature; moreover, the GCG model is nearly flat, as required by Cosmic Microwave Background (CMB) observations.

astro-ph↗

arXiv2005

Gravitational baryogenesis in Gauss-Bonnet braneworld cosmology

The mechanism of gravitational baryogenesis, based on the CPT-violating gravitational interaction between the derivative of the Ricci scalar curvature and the baryon-number current, is investigated in the context of the Gauss-Bonnet braneworld cosmology. We study the constraints on the fundamental five-dimensional gravity scale, the effective scale of B-violation and the decoupling temperature, for the above mechanism to generate an acceptable baryon asymmetry during the radiation-dominated era. The scenario of gravitational leptogenesis, where the lepton-number violating interactions are associated with the neutrino mass seesaw operator, is also considered.

hep-ph↗

arXiv2005

Supernovae constraints on models of dark energy revisited

We use the Type Ia Supernova gold sample data of Riess {\it et al} in order to constrain three models of dark energy. We study the Cardassian model, the Dvali-Turner gravity modified model and the generalized Chaplygin gas model of dark energy - dark matter unification. In our best fit analysis for these three dark energy proposals we consider flat model and the non-flat model priors. We also discuss the degeneracy of the models with the XCDM model through the computation of the so-called jerk parameter.

astro-ph↗

arXiv2004

The Revival of the Unified Dark Energy-Dark Matter Model ?

We consider the generalized Chaplygin gas (GCG) proposal for unification of dark energy and dark matter and show that it admits an unique decomposition into dark energy and dark matter components once phantom-like dark energy is excluded. Within this framework, we study structure formation and show that difficulties associated to unphysical oscillations or blow-up in the matter power spectrum can be circumvented. Furthermore, we show that the dominance of dark energy is related to the time when energy density fluctuations start deviating from the linear $δ\sim a$ behaviour.

astro-ph↗

arXiv2004

Time Evolution of the Fine Structure Constant in a Two-Field Quintessence Model

We examine the variation of the fine structure constant in the context of a two-field quintessence model. We find that, for solutions that lead to a transient late period of accelerated expansion, it is possible to fit the data arising from quasar spectra and comply with the bounds on the variation of $α$ from the Oklo reactor, meteorite analysis, atomic clock measurements, Cosmic Microwave Background Radiation and Big Bang Nucleosynthesis. That is more difficult if we consider solutions corresponding to a late period of permanent accelerated expansion.

astro-ph↗

arXiv2004

Sneutrino brane inflation and leptogenesis

Modifications to the Friedmann equation in brane cosmology can have important implications for early universe phenomena such as inflation and the generation of the baryon asymmetry. We study a simple scenario of chaotic brane inflation where, in a minimal supersymmetric seesaw model, the scalar superpartner of a heavy singlet Majorana neutrino drives inflation and, simultaneously, generates the required lepton asymmetry through its direct out-of-equilibrium decays after the inflationary era. For a gravitino mass in the range 100 GeV - 1 TeV, we find that successful nucleosynthesis and leptogenesis in this framework require that the 5D Planck mass is in the range M5 ~ 10^10 - 10^13 GeV and the reheating temperature Trh ~ 10^6 - 10^8 GeV.

hep-ph↗

arXiv2004

WMAP Constraints on a Quintessence Model

We use the results from the Wilkinson Microwave Anisotropy Probe (WMAP) for the locations of peaks and troughs of the Cosmic Microwave Background (CMB) power spectrum, together with constraints from large-scale structure, to study a quintessence model in which the pure exponential potential is modified by a polynomial factor. Our analysis, in the $(Ω_m, h, n_s)$ cosmological parameters space shows that this quintessence model is favoured compared to $Λ$CDM for $n_s\approx 1$ and relatively high values of early quintessence; for $n_s<1$, quintessence and $Λ$CDM give similar results, except for high values of early quintessence, in which case $Λ$CDM is favoured.

astro-ph↗