arXiv subjects

Nelson Videla

Publications and source records attributed to Nelson Videla.

33 records · Page 2Linked to original sources

arXiv2017

Impact of generalized dissipative coefficient on warm inflationary dynamics in the light of latest Planck data

The warm inflation scenario in view of the modified Chaplygin gas is studied. We consider the inflationary expansion is driven by a standard scalar field whose decay ratio $Γ$ has a generic power law dependence with the scalar field $ϕ$ and the temperature of the thermal bath $T$. By assuming an exponential power law dependence in the cosmic time for the scale factor $a(t)$, corresponding to the intermediate inflation model, we solve the background and perturbative dynamics considering that our model evolves according to (i) weak dissipative regime and (ii) strong dissipative regime. Specifically, we find explicit expressions for the dissipative coefficient, scalar potential, and the relevant inflationary observables as the scalar power spectrum, scalar spectral index, and tensor-to-scalar ratio. The free parameters characterizing our model are constrained by considering the essential condition for warm inflation, the conditions for the model evolves according to weak or strong dissipative regime, and the 2015 Planck results through the $n_s-r$ plane.

gr-qc↗

arXiv2017

Dynamics of warm power-law plateau inflation with a generalized inflaton decay rate: predicctions and constraints after Planck 2015

In the present work we study the consequences of considering a new family of single-field inflation models, called power-law plateau inflation, in the warm inflation framework. We consider the inflationary expansion is driven by a standard scalar field with a decay ratio $Γ$ having a generic power-law dependence with the scalar field $ϕ$ and the temperature of the thermal bath $T$ given by $Γ(ϕ,T)=C_ϕ\,\frac{T^m}{ϕ^{m-1}}$. Assuming that our model evolves according to the strong dissipative regime, we study the background and perturbative dynamics, obtaining the most relevant inflationary observables as the scalar power spectrum, the scalar spectral index and its running, and the tensor-to-scalar ratio. The free parameters characterizing our model are constrained by considering the essential condition for warm inflation, the conditions for the model evolves according to the strong dissipative regime, and the 2015 Planck results through the $n_s-r$ plane. For completeness, we study the predictions in the $n_s-dn_s/d\ln k$ plane. The model is consistent with a strong dissipative dynamics and predicts values for the tensor-to-scalar ratio and for the running of the scalar spectral index consistent with current bounds imposed by Planck, and we conclude that the model is viable.

gr-qc↗

arXiv2017

Hamilton-Jacobi approach for quasi-exponential inflation: predictions and constraints after Planck 2015 results

In the present work we study the consequences of considering an inflationary universe model in which the Hubble rate has a quasi-exponential dependence in the inflaton field, given by $H(ϕ)=H_{inf}\exp \left[\frac{\fracϕ{m_p}}{p\left(1+\fracϕ{m_p}\right)}\right]$. We analyze the inflation dynamics under the Hamilton-Jacobi approach, which allows us to consider $H(ϕ)$, rather than $V(ϕ)$, as the fundamental quantity to be specified. By comparing the theoretical predictions of the model together with the allowed contour plots in the $n_s-r$ plane and the amplitude of primordial scalar perturbations from the latest Planck data, the parameters charactering this model are constrained. The model predicts values for the tensor-to-scalar ratio $r$ and for the running of the scalar spectral index $dn_s/ d\ln k$ consistent with the current bounds imposed by Planck, and we conclude that the model is viable.

gr-qc↗

arXiv2016

Natural Inflation on the brane with a TeV-scale gravity: Parameter constraints after Planck 2015

In the present work we have studied Natural Inflation in the framework of the Randall-Sundrum II brane model (RS-II) in the light of the latest Planck results. Adopting the Randall-Sundrum fine-tuning, the model is characterized by 3 parameters in total, namely the 5-dimensional Planck mass $M_5$ and the two mass scales of the inflaton potential $f$ and $Λ$. We show in the $n_s-r$ plane the theoretical predictions of the model together with the allowed contour plots, and we conclude that the model is viable. By using the Planck results only it is possible to determine the two mass scales of the inflaton potential in terms of $M_5$, which remains undetermined. However, there are several good theoretical reasons to consider a higher-dimensional Planck mass of the order of $10 TeV$, which is compatible with primordial nucleosynthesis. If we insist on considering a $M_5$ of this order of magnitude all parameters are known and a sub-Planckian excursion of the inflaton scalar field is achieved.

gr-qc↗

arXiv2016

Instability in interacting dark sector: An appropriate Holographic Ricci dark energy model

In this paper we investigate the consequences of phantom crossing considering the perturbative dynamics in models with interaction in their dark sector. By mean of a general study of gauge-invariant variables in comoving gauge, we relate the sources of instabilities in the structure formation process with the phantom crossing. In order to illustrate these relations and its consequences in more detail, we consider a specific case of an holographic dark energy interacting with dark matter. We find that in spite of the model is in excellent agreement with observational data at background level, however it is plagued of instabilities in its perturbative dynamics. We reconstruct the model in order to avoid these undesirable instabilities, and we show that this implies a modification of the concordance model at background. Also we find drastic changes on the parameters space in our model when instabilities are avoided.

gr-qc↗

arXiv2016

Warm intermediate inflationary Universe model in the presence of a Generalized Chaplygin Gas

A warm intermediate inflationary model in the context of Generalized Chaplygin Gas is investigated. We study this model in the weak and strong dissipative regimes, considering a generalized form of the dissipative coefficient $Γ=Γ(T,ϕ)$, and we describe the inflationary dynamics in the slow-roll approximation. We find constraints on the parameters in our model considering the Planck 2015 data, together with the condition for warm inflation $T>H$, and the conditions for the weak and strong dissipative regimes.

gr-qc↗

arXiv2015

Warm $\fracλ{4}ϕ^{4}$ inflationary universe model in light of Planck 2015 results

In the present work we show that warm chaotic inflation characterized by a simple $\fracλ{4}ϕ^{4}$ self-interaction potential for the inflaton, excluded by current data in standard cold inflation, and by an inflaton decay rate proportional to the temperature, is in agreement with the latest Planck data. The parameters of the model are constrained, and our results show that the model predicts a negligible tensor-to-scalar ratio in the strong dissipative regime, while in the weak dissipative regime the tensor-to-scalar ratio can be large enough to be observed.

gr-qc↗

arXiv2015

Warm intermediate inflation in the Randall-Sundrum II model in the light of Planck 2015 and BICEP2 results: A general dissipative coefficient

A warm inflationary Universe in the Randall-Sundrum II model during intermediate inflation is studied. For this purpose, we consider a general form for the dissipative coefficient $Γ(T,ϕ)=C_ϕ\,\frac{T^{m}}{ϕ^{m-1}}$, and also analyze this inflationary model in the weak and strong dissipative regimes. We study the evolution of the Universe under the slow-roll approximation and find solutions to the full effective Friedmann equation in the brane-world framework. In order to constrain the parameters in our model, we consider the recent data from the BICEP2-Planck 2015 data together with the necessary condition for warm inflation $T>H$, and also the condition from the weak (or strong) dissipative regime.

gr-qc↗

arXiv2014

Warped DGP model in warm intermediate inflation with a general dissipative coefficient in light of BICEP2 and Planck results

A warm inflationary universe scenario on a warped Dvali-Gabadadze-Porrati brane during intermediate inflation is studied. We consider a general form for the dissipative coefficient $Γ(T,ϕ)\propto T^{m}/ϕ^{m-1}$, and also study this model in the weak and strong dissipative regimes. We analyze the evolution of the universe in the slow-roll approximation, and find the exact solutions to the equations of motion. In both regimes, we utilize recent data from the BICEP2 experiment and also from the Planck satellite to constrain the parameters in our model in accordance with the theory of cosmological perturbations.

gr-qc↗

arXiv2014

General dissipative coefficient in warm intermediate inflation in loop quantum cosmology in light of Planck and BICEP2

In this paper, we study a warm intermediate inflationary model with a general form for the dissipative coefficient $Γ(T,ϕ)=C_ϕ\,T^{m}/ϕ^{m-1}$ in the context of loop quantum cosmology. We examine this model in the weak and strong dissipative regimes. In general, we discuss in great detail the characteristics of this model in the slow-roll approximation. Also, we assume that the modifications to perturbation equations result exclusively from Hubble rate. In this approach, we use recent astronomical observations from Planck and BICEP2 experiments to restrict the parameters in our model.

gr-qc↗

arXiv2014

The generalized second law of thermodynamics for interacting $f(R)$ gravity

We examine the validity of the generalized second law (GSL) of gravitational thermodynamics in the context of interacting $f(R)$ gravity. We take into account that the boundary of the universe to be confined by the dynamical apparent horizon in a flat FRW universe. We study the effective equation of state, deceleration parameter and GSL in this interaction-framework. We find that the evolution of the total entropy increases through the interaction term. As a example, we consider a $f(R)$ gravity with a power-law dependence on the curvature $R$. Here, we find exact solutions for a model in which the interaction term is related to the total energy density of matter.

gr-qc↗

arXiv2013

General dissipative coefficient in warm intermediate and logamediate inflation

We study a general form for the dissipative coefficient $Γ(T,ϕ)=C_ϕ\,T^{m}/ϕ^{m-1}$ in the context of warm intermediate and logamediate inflationary universe models. We analyze these models in the weak and strong dissipative regimes. In the slow-roll approximation, we describe in great detail the characteristics of these models. In both regimes, we use recent data from the WMAP nine-year data and Planck data to constrain the parameters appearing in our models.

gr-qc↗

arXiv2013

Intermediate inflation on the brane and warped DGP models

Brane and warped Dvali-Gabadadze-Porrati inflationary universe models in the context of intermediate inflation are studied. In both models we consider that the energy density is a standard scalar field and we discuss the evolution of the universe during the slow-roll inflation. Also, we describe the conditions for these models. The corresponding Wilkinson Microwave Anisotropy Probe seven year data are utilized to fix some parameters in our models. Our results are compared to those found in General Relativity.

gr-qc↗

arXiv2013

Intermediate-Generalized Chaplygin Gas inflationary universe model

An intermediate inflationary universe model in the context of a generalized Chaplygin gas is considered. For the matter we consider two different energy densities; a standard scalar field and a tachyon field, respectively. In general, we discuss the conditions of an inflationary epoch for these models. We also, use recent astronomical observations from Wilkinson Microwave Anisotropy Probe seven year data for constraining the parameters appearing in our models.

astro-ph.CO↗

arXiv2010

Intermediate inflation in Gauss-Bonnet braneworld

In this article we study an intermediate inflationary universe models using the Gauss-Bonnet brane. General conditions required for these models to be realizable are derived and discussed. We use recent astronomical observations to constraint the parameters appearing in the model.

astro-ph.CO↗