Approximate consistency condition from a running spectral index in slow-roll inflationary models

2006 ◽  
Vol 73 (10) ◽  
Author(s):  
Daniel J. H. Chung ◽  
Antonio Enea Romano
Keyword(s):  
Spectral Index ◽  
Consistency Condition ◽  
Slow Roll ◽  
Inflationary Models

scholarly journals Deviation from Slow-Roll Regime in the EGB Inflationary Models with r ∼ Ne−1

Universe ◽  
2021 ◽  
Vol 7 (6) ◽  
pp. 181
Author(s):  
Ekaterina O. Pozdeeva
Keyword(s):  
Spectral Index ◽  
Effective Potential ◽  
Evolution Equations ◽  
Potential Approach ◽  
Bonnet Gravity ◽  
Slow Roll ◽  
Inflationary Parameters ◽  
Inflationary Models

We consider Einstein–Gauss–Bonnet (EGB) inflationary models using the effective potential approach. We present evolution equations in the slow-roll regime using the effective potential and the tensor-to-scalar ratio. The choice of the effective potential is related to an expression of the spectral index in terms of e-folding number Ne. The satisfaction of the slow-roll regime is mostly related to the form of the tensor-to-scalar ratio r. The case of r∼1/Ne2 leads to a generalization of α-attractors inflationary parameters to Einstein–Gauss–Bonnet gravity with exponential effective potential. Moreover, the cosmological attractors include models with r∼1/Ne. And we check the satisfaction of the slow-roll regime during inflation for models with r∼1/Ne.

scholarly journals Gauge inflation by kinetic coupled gravity

2014 ◽  
Vol 29 (30) ◽  
pp. 1450161 ◽  
Author(s):  
F. Darabi ◽  
A. Parsiya
Keyword(s):  
Field Theory ◽  
Gauge Field ◽  
Gauge Field Theory ◽  
Einstein Tensor ◽  
Abelian Gauge ◽  
Metric Tensor ◽  
New Class ◽  
Slow Roll ◽  
Set Up ◽  
Inflationary Models

Recently, a new class of inflationary models, so-called gauge-flation or non-Abelian gauge field inflation has been introduced where the slow-roll inflation is driven by a non-Abelian gauge field A with the field strength F. This class of models are based on a gauge field theory having F2 and F4 terms with a non-Abelian gauge group minimally coupled to gravity. Here, we present a new class of such inflationary models based on a gauge field theory having only F2 term with non-Abelian gauge fields non-minimally coupled to gravity. The non-minimal coupling is set up by introducing the Einstein tensor besides the metric tensor within the F2 term, which is called kinetic coupled gravity. A perturbation analysis is performed to confront the inflation under consideration with Planck and BICEP2 results

scholarly journals Inflationary cosmology in unimodular F(T) gravity

2017 ◽  
Vol 32 (21) ◽  
pp. 1750114 ◽  
Author(s):  
Kazuharu Bamba ◽  
Sergei D. Odintsov ◽  
Emmanuel N. Saridakis
Keyword(s):  
Spectral Index ◽  
Teleparallel Gravity ◽  
Specific Model ◽  
Inflationary Cosmology ◽  
Model Parameters ◽  
De Sitter ◽  
Reconstruction Procedure ◽  
Additional Advantage ◽  
Slow Roll ◽  
Good Agreement

We investigate the inflationary realization in the context of unimodular F(T) gravity, which is based on the F(T) modification of teleparallel gravity, in which one imposes the unimodular condition through the use of Lagrange multipliers. We develop the general reconstruction procedure of the F(T) form that can give rise to a given scale-factor evolution, and then we apply it in the inflationary regime. We extract the Hubble slow-roll parameters that allow us to calculate various inflation-related observables, such as the scalar spectral index and its running, the tensor-to-scalar ratio, and the tensor spectral index. Then, we examine the particular cases of de Sitter and power-law inflation, of Starobinsky inflation, as well as inflation in a specific model of unimodular F(T) gravity. As we show, in all cases the predictions of our scenarios are in a very good agreement with Planck observational data. Finally, inflation in unimodular F(T) gravity has the additional advantage that it always allows for a graceful exit for specific regions of the model parameters.

scholarly journals NONCOMMUTATIVE DECRUMPLING INFLATION AND RUNNING OF THE SPECTRAL INDEX

2005 ◽  
Vol 14 (03n04) ◽  
pp. 621-633 ◽  
Author(s):  
FOROUGH NASSERI ◽  
S. A. ALAVI
Keyword(s):  
Noncommutative Geometry ◽  
Spectral Index ◽  
Time Variability ◽  
Inflation Model ◽  
Slow Roll ◽  
Spatial Dimensions

We present a new inflation model, known as noncommutative decrumpling inflation, in which space has noncommutative geometry with time variability of the number of spatial dimensions. Within the framework of noncommutative decrumpling inflation, we compute both the spectral index and its running. Our results show the effects of both time variability of the number of spatial dimensions and noncommutative geometry on the spectral index and its running. Two classes of examples have been studied and comparisons made with the standard slow-roll formulae. We conclude that the effects of noncommutative geometry on the spectral index and its running are much smaller than the effects of time variability of spatial dimensions.

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.

Cosmography parameters in inflationary scenario and their interrelation with slow-roll parameters

2018 ◽  
Vol 33 (26) ◽  
pp. 1850151 ◽  
Author(s):  
Dipanjana Das ◽  
Sourav Dutta ◽  
Subenoy Chakraborty
Keyword(s):  
Spectral Index ◽  
Inflationary Scenario ◽  
Slow Roll

This work investigates the inflationary era with slow-roll approximation in the perspective of cosmography parameters. The slow-roll parameters are determined in terms of cosmography parameters and then the cosmography parameters are constrained by the slow-roll approximations. The three important parameters in inflationary scenario, namely the spectral index, tensor to scalar ratio and number of e-foldings, are also expressed in terms of cosmography parameters. Finally, all relevant parameters are analyzed graphically for a known inflationary solution.

scholarly journals BICEP2 constrains composite inflation

2014 ◽  
Vol 23 (08) ◽  
pp. 1450070 ◽  
Author(s):  
Phongpichit Channuie
Keyword(s):  
Spectral Index ◽  
Cosmological Parameters ◽  
Inflationary Model ◽  
Composite State ◽  
Planck Data ◽  
Strongly Coupled ◽  
Yang Mills ◽  
Composite Models ◽  
Single Field ◽  
Inflationary Models

In light of BICEP2, we re-examine single field inflationary models in which the inflation is a composite state stemming from various four-dimensional strongly coupled theories. We study in the Einstein frame a set of cosmological parameters, the primordial spectral index ns and tensor-to-scalar ratio r, predicted by such models. We confront the predicted results with the joint Planck data, and with the recent BICEP2 data. We constrain the number of e-foldings for composite models of inflation in order to obtain a successful inflation. We find that the minimal composite inflationary model is fully consistent with the Planck data. However it is in tension with the recent BICEP2 data. The observables predicted by the glueball inflationary model can be consistent with both Planck and BICEP2 contours if a suitable number of e-foldings are chosen. Surprisingly, the super Yang–Mills inflationary prediction is significantly consistent with the Planck and BICEP2 observations.

scholarly journals General Slow-Roll Inflation in f(R) Gravity under the Palatini Approach

Symmetry ◽  
2020 ◽  
Vol 12 (12) ◽  
pp. 1958
Author(s):  
Sabit Bekov ◽  
Kairat Myrzakulov ◽  
Ratbay Myrzakulov ◽  
Diego Sáez-Chillón Gómez
Keyword(s):  
Scalar Field ◽  
Simple Model ◽  
Spectral Index ◽  
Effective Potential ◽  
Modified Gravity ◽  
Palatini Formalism ◽  
Slow Roll ◽  
Slow Roll Inflation

Slow-roll inflation is analyzed in the context of modified gravity within the Palatini formalism. As shown in the literature, inflation in this framework requires the presence of non-traceless matter; otherwise, it does not occur just as a consequence of the nonlinear gravitational terms of the action. Nevertheless, by including a single scalar field that plays the role of the inflaton, slow-roll inflation can be performed in these theories, where the equations lead to an effective potential that modifies the dynamics. We obtain the general slow-roll parameters and analyze a simple model to illustrate the differences introduced by the gravitational terms under the Palatini approach, and the modifications on the spectral index and the tensor to scalar ratio predicted by the model.

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.

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.

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