Inflationary Universe Models Research Articles

Weak and strong warm logamediate anisotropic inflationary universe model

In this paper we investigate a warm inflation scenario of a locally rotationally symmetric Bianchi type-I model using a background of modified Chaplygin gas. We determine the field equations and perturbations parameters, such as the scalar power spectrum, scalar spectral index, scalar potential, and tensor-to-scalar ratio under the slow roll approximation. We determine these parameters in the direction of the Hubble parameter during both the weak and strong logamediate inflationary regimes. These cosmological parameters show that the anisotropic model is compatible with WMAP 7 from the 2018 Planck observational data.

Warm G inflation: Intermediate model

A warm-intermediate inflationary universe model is studied in the presence of the Galileon coupling $G(\phi,X)=g(\phi)X$. General conditions required for successful inflation are deduced and discussed from the background and cosmological perturbations under slow-roll approximation. In our analyze we assume that the dynamics of our model evolves accordingly two separate regimes, namely $3g\dot{\phi}H\gg 1+R$, i.e., when the Galileon term dominates over the standard kinetic term and the dissipative ratio, and secondly in the regime where both $3g\dot{\phi}H$ and $R$ become of the same order than unity. For these regimes and assuming that the coupling parameter $g=g_0=$ constant, we consider two different dissipative coefficients $\Gamma$; one constant and the other being a function of the inflaton field. Furthermore, we find the allowed range in the space of parameters for our G-warm model by considering the latest data of Planck and also the BICEP2/Keck-Array data from the $r=r(n_s)$ plane, in combination with the conditions in which the Galileon term dominates and the thermal fluctuations of the inflaton field predominate over the quantum ones.

Reconstructing warm inflation

The reconstruction of a warm inflationary universe model from the scalar spectral index n_S(N) and the tensor to scalar ratio r(N) as a function of the number of e-folds N is studied. Under a general formalism we find the effective potential and the dissipative coefficient in terms of the cosmological parameters n_S and r considering the weak and strong dissipative stages under the slow roll approximation. As a specific example, we study the attractors for the index n_S given by n_{S}-1propto N^{-1} and for the ratio rpropto N^{-2}, in order to reconstruct the model of warm inflation. Here, expressions for the effective potential V(phi ) and the dissipation coefficient Gamma (phi ) are obtained.

Predictions of Spectral Parameters by Several Inflationary Universe Models in Light of the Planck Results

I give a review of predictions of values of spectral parameters for a large number of inflationary models. The present review includes detailed deductions and information about the approximations that have been made, written in a style that is suitable for text book authors. The Planck data have the power of falsifying several models of inflation as shown in the present paper. Furthermore, they fix the beginning of the inflationary era to a time about 10−36 s, and the typical energy of a particle at this point of time to 1016 GeV, only a few orders of magnitude less than the Planck energy, and at least 12 orders of magnitude larger than the most energetic particle produced by CERN’s particle accelerator, LHC. This is a phenomenological review with contents as given in the list below. It includes systematic presentations of the different types of slow roll parameters that have been in use, and also of the N-formalism.

Warm generalized cosmic Chaplygin gas inflation inspired by generalized dissipative coefficient

We examine the warm inflationary universe model in the presence of generalized cosmic Chaplygin gas and standard scalar field. We assume the generalized dissipative coefficient and corresponding weak and strong dissipative regimes. In this framework, we analyze the characteristics of inflationary dynamics under the slow-roll approximations. Under these approximations, we formulate the important inflationary parameters, such as scalar spectral index, scalar and tensor power spectrum, tensor-to-scalar ratio etc. It is interesting to note that our results for these inflationary parameters are well corroborated with the recent observational data like WMAP7, WMAP9 and Planck data.

Intermediate inflation in a generalized induced-gravity scenario

An intermediate inflationary Universe model in the context of non-minimal coupling to the scalar curvature is analyzed. We will conduct our analysis in the slow-roll approximation of the inflationary dynamics and the cosmological perturbations considering a coupling of the form F(varphi )=kappa +xi _nvarphi ^n. Considering the trajectories in the r–n_s plane from the Planck data, we find the constraints on the parameter space in our model.

Hamilton\u2013Jacobi 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(phi )=H_{mathrm{inf}}exp [frac{frac{phi }{m_mathrm{p}}}{pleft( 1+frac{phi }{m_mathrm{p}}right) }]. We analyze the inflation dynamics under the Hamilton–Jacobi approach, which allows us to consider H(phi ), rather than V(phi ), as the fundamental quantity to be specified. By comparing the theoretical predictions of the model together with the allowed contour plots in the n_mathrm{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 mathrm{d}n_mathrm{s}/ mathrm{d}ln k consistent with the current bounds imposed by Planck, and we conclude that the model is viable.

Quantum-gravitational effects on gauge-invariant scalar and tensor perturbations during inflation: The slow-roll approximation

We continue our study on corrections from canonical quantum gravity to the power spectra of gauge-invariant inflationary scalar and tensor perturbations. A direct canonical quantization of a perturbed inflationary universe model is implemented, which leads to a Wheeler-DeWitt equation. For this equation, a semiclassical approximation is applied in order to obtain a Schroedinger equation with quantum-gravitational correction terms, from which we calculate the corrections to the power spectra. We go beyond the de Sitter case discussed earlier and analyze our model in the first slow-roll approximation, considering terms linear in the slow-roll parameters. We find that the dominant correction term from the de Sitter case, which leads to an enhancement of power on the largest scales, gets modified by terms proportional to the slow-roll parameters. A correction to the tensor-to-scalar ratio is also found at second order in the slow-roll parameters. Making use of the available experimental data, the magnitude of these quantum-gravitational corrections is estimated. Finally, the effects for the temperature anisotropies in the cosmic microwave background are qualitatively obtained.

Chaplygin gas inspired scalar fields inflation via well-known potentials

Brane inflationary universe models in the context of modified Chaplygin gas and generalized cosmic Chaplygin gas are being studied. We develop these models in view of standard scalar and tachyon fields. In both models, the implemented inflationary parameters such as scalar and tensor power spectra, scalar spectral index and tensor to scalar ratio are derived under slow roll approximations. We also use chaotic and exponential potential in high energy limits and discuss the characteristics of inflationary parameters for both potentials. These models are compatible with recent astronomical observations provided by \(\mbox{WMAP}7{+}9\) and Planck data, i.e., \(\eta_{s}=1.027\pm0.051, 1.009\pm0.049, 0.096\pm0.025\) and \(r<0.38, 0.36, 0.11\).

Dynamics of warm Chaplygin gas inflationary models with quartic potential

Warm inflationary universe models in the context of generalized chaplygin gas, modified chaplygin gas, generalized cosmic chaplygin gas are being studied. The dissipative coefficient of the form $\Gamma\propto T$, weak and strong dissipative regimes are being considered. We use quartic potential $\frac{\lambda_{*}\phi^{4}}{4}$, which is ruled out by current data in cold inflation but in our models it is analyzed that it is in agreement with the WMAP$9$ and latest Planck data. In these scenarios, the power spectrum, spectral index, and tensor to scalar ratio are being examined under the slow roll approximation. We show the dependence of tensor scalar ratio $r$ on spectral index $n_{s}$ and observe that the range of tensor scalar ratio is $r<0.05$ in generalized chaplygin gas, $r<0.15$ in modified chaplygin gas, and $r<0.12$ in generalized cosmic chaplygin gas models. Our results are in agreement with recent observational data like WMAP$9$ and latest Planck data.

Inflationary weak anisotropic model with general dissipation coefficient

This paper explores the dynamics of warm intermediate and logamediate inflationary models during weak dissipative regime with a general form of dissipative coefficient. We analyze these models within the framework of locally rotationally symmetric Bianchi type I universe. In both cases, we evaluate solution of inflaton, effective scalar potential, dissipative coefficient, slow-roll parameters, scalar and tensor power spectra, scalar spectral index and tensor to scalar ratio under slow-roll approximation. We constrain the model parameters using recent data and conclude that anisotropic inflationary universe model with generalized dissipation coefficient remains compatible with WMAP9, Planck and BICEP2 data.

Tachyon Warm Intermediate and Logamediate Inflation in the Brane World Model in the Light of Planck Data

Tachyon inflationary universe model on the brane in the context of warm inflation is studied. In slow-roll approximation and in longitudinal gauge, we find the primordial perturbation spectrums for this scenario. We also present the general expressions of the tensor-scalar ratio, scalar spectral index, and its running. We develop our model by using exponential potential; the characteristics of this model are calculated in great detail. We also study our model in the context of intermediate (where scale factor expands asa=a0exp⁡Atf) and logamediate (where the scale factor expands asa=a0exp⁡Aln⁡tν) models of inflation. In these two sectors, dissipative parameter is considered as a constant parameter and a function of tachyon field. Our model is compatible with observational data. The parameters of the model are restricted by Planck data.

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 $\Gamma=\Gamma(T,\phi)$, 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.

General dissipative coefficient in strong anisotropic inflation

In this paper, we analyze the effects of generalized dissipative coefficient on the dynamics of warm intermediate and logamediate inflationary universe models during strong dissipative regime. We explore these models within the framework of locally rotationally symmetric Bianchi type I universe. In both cases, we evaluate inflaton, effective scalar potential, dissipative coefficient, slow-roll parameters, scalar and tensor power spectra, scalar spectral index and tensor-scalar ratio under slow-roll approximation. The inflationary model as well as perturbed parameters are constrained using recent data. We conclude that intermediate anisotropic inflationary universe model with generalized dissipative coefficient remains compatible with WMAP9, Planck and BICEP2 data while \(n=1\) (arbitrary integer) is the only consistent case during logamediate era. Also, both of these models interpolate between weak and strong regimes.

Warm-viscous inflation model on the brane in light of Planck data

In the present work, a warm inflationary Universe model with viscous pressure on the brane in a high-dissipation regime is studied. We derive a condition that is required for this model to be realized in a slow-roll approximation. We also present analytic expressions for the density perturbation and the amplitude of the tensor perturbation in a longitudinal gauge. General expressions of the tensor-to-scalar ratio and the scalar spectral index and its running are obtained. We develop our model using chaotic potential. The characteristics of the model are calculated for two specific cases: (1) when the dissipative parameter Γ and the bulk viscous parameter ζ are constant parameters and (2) with the dissipative parameter as a function of scalar field ϕ and the bulk viscous parameter as a function of radiation-matter mixture energy density ρ. The parameters of the model are restricted by WMAP9 and Planck observational data.

Warm Chaplygin inflation in loop quantum cosmology in light of Planck data

The warm Chaplygin inflationary universe model in the context of the effective field theory of loop quantum cosmology (LQC) is studied. In the slow-roll phase of inflation primordial perturbation spectrums, tensor-to-scalar ratio and spectral indices of our model are presented. Using chaotic potential, we present the main characteristics of this model in great detail. The parameters of the model are restricted by recent observational results i.e. WMAP9 and Planck data.

Inhomogeneous viscous fluid in anisotropic inflationary universe

In this paper, we study inhomogeneous viscous fluid for inflation in the framework of locally rotationally symmetric Bianchi type I universe model. We consider an inhomogeneous equation of state with viscosity term to ensure a graceful exit from inflationary period. In order to study inflationary perturbations, we evaluate slow-roll parameters, scalar and tensor power spectra, scalar spectral index, tensor to scalar ratio for scalar field and inhomogeneous viscous fluid. It is concluded that our anisotropic inflationary universe model with inhomogeneous viscous fluid is consistent with recent data in a specific range of the model parameters.

Scalar perturbation in warm tachyon inflation in LQC in light of Plank and BICEP2

We study warm-tachyon inflationary universe model in the context of the effective field theory of loop quantum cosmology. In slow-roll approximation the primordial perturbation spectrums for this model are calculated. We also obtain the general expressions of the tensor-to-scalar ratio and scalar spectral index. We develop this model by using exponential potential, the characteristics of this model are presented in great details. The parameters of the model are restricted by recent observational data from Planck, WMAP9 and BICEP2.

Dynamics of warm inflation with gauge fields in Bianchi type I universe model

In this paper, we study the dynamics of warm inflation in which slow-roll inflation is driven by non-Abelian gauge fields. To this end, we use the geometry of locally rotationally symmetric Bianchi type I universe model. We construct dynamical equations, i.e., first model field equation, energy conservation equations and equation of motion under slow-roll approximation. In order to discuss inflationary perturbations, we evaluate parameters like scalar and tensor power spectra as well as scalar and tensor spectral indices. We also evaluate inflaton, directional Hubble parameter, slow-roll and perturbation parameters as well as tensor-scalar ratio as a function of inflaton during intermediate and logamediate inflationary eras. It is concluded that anisotropic inflationary universe model with non-Abelian gauge fields remains compatible with WMAP7.

Cosmological perturbations in warm-tachyon inflationary universe model with viscous pressure

We study the warm-tachyon inflationary universe model with viscous pressure in high-dissipation regime. General conditions which are required for this model to be realizable are derived in the slow-roll approximation. We present analytic expressions for density perturbation and amplitude of tensor perturbation in longitudinal gauge. Expressions of tensor-to-scalar ratio, scalar spectral index and its running are obtained. We develop our model by using exponential potential, the characteristics of this model are calculated for two specific cases in great details: 1. Dissipative parameter Γ and bulk viscous parameter ζ are constant parameters. 2. Dissipative parameter is a function of tachyon field ϕ and bulk viscous parameter is a function of matter-radiation mixture energy density ρ. The parameters of the model are restricted by recent observational data from the nine-year Wilkinson microwave anisotropy probe (WMAP9), Planck and BICEP2 data.