Shaft potential inspired warm inflation

2017 ◽  
Vol 14 (06) ◽  
pp. 1750088 ◽  
Author(s):  
Abdul Jawad ◽  
Amara Ilyas ◽  
Sarfraz Ahmad
Keyword(s):  
Scalar Field ◽  
Spectral Index ◽  
Power Spectra ◽  
Spectral Indices ◽  
Tensor Power ◽  
Planck Data ◽  
Warm Inflation ◽  
Slow Roll ◽  
Scalar Spectral Index ◽  
Inflationary Parameters

We discuss the warm inflation in the presence of shaft potential [Formula: see text], tachyon scalar field and the generalized form of dissipative coefficient [Formula: see text]. In this respect, we investigate the inflationary parameters (slow-roll parameters, number of e-folds, scalar-tensor power spectra, spectral indices, tensor-to-scalar ratio and running of scalar spectral index) in both strong and weak dissipative regimes. It is interesting to mention that our inflationary parametric results (tensor-scalar ratio, spectral index and running of spectral) are consistent with the recent observational data such as BICEP[Formula: see text], WMAP[Formula: see text] and latest Planck data.

Power-law plateau and inverse symmetric inflation

2018 ◽  
Vol 27 (08) ◽  
pp. 1850087 ◽  
Author(s):  
Abdul Jawad ◽  
Shahid Chaudhary
Keyword(s):  
Scalar Field ◽  
Power Spectrum ◽  
Spectral Index ◽  
Power Law ◽  
Field Model ◽  
Chaplygin Gas ◽  
Generalized Chaplygin Gas ◽  
Planck Data ◽  
Inflationary Parameters ◽  
Ratio Versus

Warm generalized Chaplygin gas inflation is being studied by assuming power-law plateau and inverse symmetric potentials with standard scalar field model. We consider strong dissipative regime with generalized dissipative coefficient and extract the various inflationary parameters such as scalar power spectrum, spectral index, tensor-to-scalar ratio and running of spectral index. It is found that both inflationary potentials favor the strong dissipative regime. Also, we construct the [Formula: see text]–[Formula: see text] (running of spectral index versus spectral index) and [Formula: see text]–[Formula: see text] (tensor-to-scalar ratio versus spectral index) planes and found that the trajectories of these planes favor WMAP 7 [Formula: see text] WMAP 9 and latest Planck data.

scholarly journals Dynamics of tachyon fields and inflation - comparison of analytical and numerical results with observation

2016 ◽  
pp. 1-8 ◽  
Author(s):  
M. Milosevic ◽  
D.D. Dimitrijevic ◽  
G.S. Djordjevic ◽  
M.D. Stojanovic
Keyword(s):  
Scalar Field ◽  
String Theory ◽  
Numerical Methods ◽  
Spectral Index ◽  
Early Universe ◽  
Slow Roll ◽  
Scalar Spectral Index ◽  
Homogeneous Universe ◽  
The Given ◽  
Good Agreement

The role tachyon fields may play in evolution of early universe is discussed in this paper. We consider the evolution of a flat and homogeneous universe governed by a tachyon scalar field with the DBI-type action and calculate the slow-roll parameters of inflation, scalar spectral index (n), and tensor-scalar ratio (r) for the given potentials. We pay special attention to the inverse power potential, first of all to V (x) ~ x?4, and compare the available results obtained by analytical and numerical methods with those obtained by observation. It is shown that the computed values of the observational parameters and the observed ones are in a good agreement for the high values of the constant X0. The possibility that influence of the radion field can extend a range of the acceptable values of the constant X0 to the string theory motivated sector of its values is briefly considered.

Reconstruction of warm Chaplygin gas inflationary models

2020 ◽  
Vol 35 (32) ◽  
pp. 2050268
Author(s):  
Abdul Jawad ◽  
Shamaila Rani ◽  
Kazuharu Bamba ◽  
Nadeem Azhar
Keyword(s):  
Spectral Index ◽  
Effective Potential ◽  
Chaplygin Gas ◽  
Index Formula ◽  
Curvature Perturbation ◽  
Warm Inflation ◽  
Scalar Spectral Index ◽  
Dissipative Coefficient ◽  
Inflationary Parameters ◽  
Friedmann Robertson Walker

By assuming the specific Chaplygin gas model, we study the reconstruction of warm inflation model with the help of tensor-to-scalar ratio [Formula: see text] and scalar spectral index [Formula: see text]. In this regard, we take flat Friedmann–Robertson–Walker (FRW) metric and discuss the general forms of dissipative coefficient [Formula: see text] as well as effective potential [Formula: see text] for two dissipative regimes i.e., the weak and strong. We use inflationary parameters such as slow-roll parameters, power spectrum of the curvature perturbation, tensor spectrum, spectral index, scalar-to-tensor ratio and Hubble parameter to find the generalized form of dissipative coefficient and effective potential. We discuss the results of dissipative coefficient and reconstructed potential in detail for the specific choice of tensor-to-scalar ratio [Formula: see text] and scalar spectral index [Formula: see text].

scholarly journals WHAT IF THE INFLATON IS A SPINOR CONDENSATE?

2009 ◽  
Vol 18 (14) ◽  
pp. 2173-2179 ◽  
Author(s):  
S. SHANKARANARAYANAN
Keyword(s):  
Scalar Field ◽  
Gravitational Wave ◽  
Spectral Index ◽  
Spinor Condensate ◽  
Slow Roll ◽  
Scalar Spectral Index ◽  
The Future ◽  
Wmap Data ◽  
Elementary Field ◽  
Canonical Scalar Field

In the usual cosmological inflationary scenarios, the scalar field — the inflaton — is usually assumed to be an elementary field. In this essay, we ask: What are the observational signatures if the scalar field is a spinor condensate? And is there a way to distinguish between the canonical scalar field and the spinor-condensate-driven models? In the homogeneous and isotropic background, we show that — although the dark-spinor (Elko) condensate leads to an acceleration equation identical to that of the canonical-scalar-field-driven inflation — the dynamics of the two models are different. In the slow-roll limit, we show that the model predicts a running of the scalar spectral index consistent with the WMAP data. We show that the consistency relations between the spinor condensate and the canonical-scalar-field-driven model are different, which we will be able to test using the future CMB and gravitational wave missions.

INFLATION AND ACCELERATING UNIVERSE IN MODIFIED MODULAR INVARIANT SUPERGRAVITY

2012 ◽  
Vol 27 (31) ◽  
pp. 1250180
Author(s):  
TOYOKAZU FUKUOKA ◽  
YUTA KOSHIMIZU ◽  
KENJI TAKAGI ◽  
HIKOYA KASARI ◽  
MITSUO J. HAYASHI
Keyword(s):  
Power Spectra ◽  
Fine Tuning ◽  
Accelerated Expansion ◽  
Wilkinson Microwave Anisotropy Probe ◽  
Accelerating Universe ◽  
Tensor Power ◽  
Modular Invariant ◽  
Slow Roll ◽  
Inflationary Parameters ◽  
The Universe

A method of explaining the recently observed acceleration of cosmic expansion as well as inflation in the early universe is presented within the same framework. The goal is to construct an inflation model based on supergravity and the slow-roll approximation (SRA) that both satisfactorily predicts observed inflationary parameters and at the same time explains the accelerated expansion of the universe. The model is based on a modification of string-based modular invariant supergravity previously proposed by the present authors. It realizes slow-roll inflation in the Einstein frame and is successful in explaining Wilkinson Microwave Anisotropy Probe (WMAP) observational data, through fine-tuning procedure of free parameters. The parameter dependence of the model is considered in detail in order to determine the range for which the SRA can be applied. Within the allowed range of parameter values, a vacuum energy of ~10-120 can be obtained, which coincides with the cosmological constant, and can play the role of dark energy in the universe. The calculated inflationary parameters fit very well to seven-year WMAP data. The ratio of the scalar and tensor power spectra is predicted to be r ~6.8 ×10-2, and this may soon be verified by observations by the Planck satellite. The non-Gaussianity parameter fNL is also estimated by the slow-roll parameters.

scholarly journals Tachyon warm inflation with the effects of loop quantum cosmology in the light of Planck 2015

2018 ◽  
Vol 27 (05) ◽  
pp. 1850056 ◽  
Author(s):  
Vahid Kamali ◽  
Spyros Basilakos ◽  
Ahmad Mehrabi ◽  
Meysam Motaharfar ◽  
Erfan Massaeli
Keyword(s):  
Scalar Field ◽  
Quantum Cosmology ◽  
Loop Quantum Cosmology ◽  
Tachyon Field ◽  
Microwave Background ◽  
Planck Data ◽  
Warm Inflation ◽  
Slow Roll ◽  
Background Data ◽  
Cosmic Microwave Background Data

We investigate the observational signatures of quantum cosmology in the Cosmic Microwave Background data provided by Planck collaboration. We apply the warm inflationary paradigm with a tachyon scalar field to the loop quantum cosmology. In this context, we first provide the basic cosmological functions in terms of the tachyon field. We then obtain the slow-roll parameters and the power spectrum of scalar and tensor fluctuations, respectively. Finally, we study the performance of various warm inflationary scenarios against the latest Planck data and we find a family of models which are in agreement with the observations.

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

2016 ◽  
Vol 2016 ◽  
pp. 1-18 ◽  
Author(s):  
V. Kamali ◽  
M. R. Setare
Keyword(s):  
Scale Factor ◽  
Brane World ◽  
Inflationary Universe ◽  
Tachyon Field ◽  
World Model ◽  
Planck Data ◽  
Warm Inflation ◽  
Slow Roll ◽  
Scalar Spectral Index ◽  
Two Sectors

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.

scholarly journals Generalization of cosmological attractor approach to Einstein–Gauss–Bonnet gravity

2020 ◽  
Vol 80 (7) ◽  
Author(s):  
Ekaterina O. Pozdeeva
Keyword(s):  
Scalar Field ◽  
Spectral Index ◽  
Leading Order ◽  
Bonnet Gravity ◽  
Inflationary Scenario ◽  
Slow Roll ◽  
Inflationary Parameters ◽  
Bonnet Term ◽  
Scalar Perturbations ◽  
Good Agreement

Abstract We construct models with the Gauss–Bonnet term multiplied by a function of the scalar field leading to an inflationary scenario. The consideration is related to the slow-roll approximation. The cosmological attractor approach gives the spectral index of scalar perturbations which is in a good agreement with modern observation and allows for variability of the tensor-to-scalar ratio. We reconstruct models with variability of parameters, which allows one to reproduce cosmological attractor predictions for inflationary parameters in an approximation of the leading order of 1/N in Einstein–Gauss–Bonnet gravity.

scholarly journals Inflation in f(R,ϕ) Gravity with Exponential Model

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Farzana Kousar ◽  
Rabia Saleem ◽  
M. Zubair
Keyword(s):  
Power Spectra ◽  
Exponential Model ◽  
Jordan Frame ◽  
Spectral Indices ◽  
Nonminimal Coupling ◽  
Tensor Power ◽  
Tensor Theory ◽  
Slow Roll ◽  
Frame Dependence ◽  
Taking Action

We are taking action of f(R) gravity with a nonminimal coupling to a massive inflaton field. A f(R,ϕ) model is chosen which leads to the scalar-tensor theory which can be transformed to Einstein frame by conformal transformation. To avoid the vagueness of the frame dependence, we evaluate the exact analytical solutions for inflationary era in Jordan frame and find a condition for graceful exit from inflation. Furthermore, we calculate the perturbed parameters (i.e., number of e-folds, slow-roll parameters, scalar and tensor power spectra, corresponding spectral indices, and tensor to scalar ratio). It is showed that the tensor power spectra lead to blue tilt for this model. The trajectories of the perturbed parameters are plotted to compare the results with recent observations.

scholarly journals Measuring the effects of loop quantum cosmology in the CMB data

2017 ◽  
Vol 26 (12) ◽  
pp. 1743023 ◽  
Author(s):  
Spyros Basilakos ◽  
Vahid Kamali ◽  
Ahmad Mehrabi
Keyword(s):  
Power Spectrum ◽  
Spectral Index ◽  
Excellent Agreement ◽  
Quantum Cosmology ◽  
Loop Quantum Cosmology ◽  
Alternative Scenario ◽  
Slow Roll ◽  
Scalar Spectral Index ◽  
Robust Prediction ◽  
Scalar Fluctuation

In this paper we investigate the observational signatures of Loop Quantum Cosmology (LQC) in the CMB data. First, we concentrate on the dynamics of LQC and we provide the basic cosmological functions. We then obtain the power spectrum of scalar and tensor perturbations in order to study the performance of LQC against the latest CMB data. We find that LQC provides a robust prediction for the main slow-roll parameters, like the scalar spectral index and the tensor-to-scalar fluctuation ratio, which are in excellent agreement within [Formula: see text] with the values recently measured by the Planck collaboration. This result indicates that LQC can be seen as an alternative scenario with respect to that of standard inflation.

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