scholarly journals Warm Inflation with Nonminimal Derivative Coupling

2014 ◽  
Vol 2014 ◽  
pp. 1-14 ◽  
Author(s):  
Kourosh Nozari ◽  
M. Shoukrani ◽  
N. Rashidi
Keyword(s):  
Scalar Field ◽  
Observational Data ◽  
Kinetic Term ◽  
Model Parameters ◽  
Detailed Calculation ◽  
Data Set ◽  
Derivative Coupling ◽  
Warm Inflation ◽  
Inflation Model ◽  
Planck Satellite

We study the effects of the nonminimal derivative coupling on the dissipative dynamics of the warm inflation where the scalar field is nonminimally coupled to gravity via its kinetic term. We present a detailed calculation of the cosmological perturbations in this setup. We use the recent observational data from the joint data set of WMAP9 + BAO +H0and also the Planck satellite data to constrain our model parameters for natural and chaotic inflation potentials. We study also the levels of non-Gaussianity in this warm inflation model and we confront the result with recent observational data from the Planck satellite.

scholarly journals CHAOTIC INFLATION ON THE RANDALL–SUNDRUM TWO-BRANE MODEL

2010 ◽  
Vol 25 (31) ◽  
pp. 2697-2713
Author(s):  
KOUROSH NOZARI ◽  
SIAMAK AKHSHABI
Keyword(s):  
Scalar Field ◽  
Field Potential ◽  
Friedmann Equation ◽  
Warp Factor ◽  
Model Parameters ◽  
Stabilization Mechanism ◽  
Brane Model ◽  
Inflation Model ◽  
Bulk Scalar Field ◽  
Chaotic Inflation

We construct an inflation model on the Randall–Sundrum I (RSI) brane where a bulk scalar field stabilizes the inter-brane separation. We study impact of the bulk scalar field on the inflationary dynamics on the brane. We proceed in two different approaches: in the first approach, the stabilizing field potential is directly appeared in the Friedmann equation and the resulting scenario is effectively a two-field inflation. In the second approach, the stabilization mechanism is considered in the context of a warp factor so that there is just one field present that plays the roles of both inflaton and stabilizer. We study constraints imposed on the model parameters from recent observations.

scholarly journals Light of Planck-2015 on Noncanonical Inflation

2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Kh. Saaidi ◽  
A. Mohammadi ◽  
T. Golanbari
Keyword(s):  
Scalar Field ◽  
Observational Data ◽  
Power Law ◽  
Hubble Parameter ◽  
Field Model ◽  
Kinetic Term ◽  
Inflationary Scenario ◽  
Slow Roll ◽  
Power Law Function ◽  
Free Parameters

Slow-roll inflationary scenario is considered in noncanonical scalar field model supposing a power-law function for kinetic term and using two formalisms. In the first approach, the potential is picked out as a power-law function, that is, the most common approach in studying inflation. Hamilton-Jacobi approach is selected as the second formalism, so that the Hubble parameter is introduced as a function of scalar field instead of the potential. Employing the last observational data, the free parameters of the model are constrained, and the predicted form of the potential and attractor behavior of the model are studied in detail.

scholarly journals LARGE NON-GAUSSIANITY FROM MULTI-BRID INFLATION

2011 ◽  
Vol 01 ◽  
pp. 108-113
Author(s):  
ATSUSHI NARUKO ◽  
MISAO SASAKI
Keyword(s):  
Scalar Field ◽  
General Feature ◽  
Present Model ◽  
The Other ◽  
Model Parameters ◽  
Exponential Potential ◽  
Inflation Model ◽  
Hybrid Inflation ◽  
Non Gaussian ◽  
Near Future

A model of multi-component hybrid inflation, dubbed multi-brid inflation, which may yield a large non-Gaussian paramter fNL, was proposed recently. In particular, for a two-brid inflation model with an exponential potential and the condition that the end of inflation is an ellipse in the field space, it was found that, while keeping the other observational quantities within the range consistent with observations, large non-Gaussianity is possible for certain inflationary trajectories. In this talk, in order to see if this result is a general feature of multi-brid inflation, we consider a model with a potential with an exponent quadratic in the scalar field components. We also consider a more general class of ellipses for the end of inflation. Focusing on the case of two-brid inflation, we find that large non-Gaussianity is also possible in the present model. Then by tuning the model parameters, we find that there exist models for which both the non-Gaussianity and the tensor-to-scalar ratio are large enough to be detected in the very near future.

scholarly journals Constant-roll inflation driven by a scalar field with nonminimal derivative coupling

2019 ◽  
Vol 28 (12) ◽  
pp. 1950159 ◽  
Author(s):  
A. Oliveros ◽  
Hernán E. Noriega
Keyword(s):  
Phase Space ◽  
Scalar Field ◽  
Exact Solutions ◽  
Free Parameter ◽  
Model Parameters ◽  
De Sitter ◽  
Einstein Tensor ◽  
Derivative Coupling ◽  
New Exact Solutions ◽  
Type Potential

In this work, we study constant-roll inflation driven by a scalar field with nonminimal derivative coupling to gravity, via the Einstein tensor. This model contains a free parameter, [Formula: see text], which quantifies the nonminimal derivative coupling and a parameter [Formula: see text] which characterizes the constant-roll condition. In this scenario, using the Hamilton–Jacobi-like formalism, an ansatz for the Hubble parameter (as a function of the scalar field) and some restrictions on the model parameters, we found new exact solutions for the inflaton potential which include power-law, de Sitter, quadratic hilltop and natural inflation, among others. Additionally, a phase-space analysis was performed and it is shown that the exact solutions associated to natural inflation and a “cosh-type” potential, are attractors.

Warm inflation and WMAP9

2017 ◽  
Vol 15 (01) ◽  
pp. 1850010 ◽  
Author(s):  
S. Davood Sadatian
Keyword(s):  
Observational Data ◽  
Warm Inflation ◽  
Inflation Model

A warm inflation model, drawn upon the vector cosmology, was applied in the present work to calculate cosmological fluctuations. Moreover, parameters of the model were constrained and compared using the latest observational data such as Planck and WMAP9.

scholarly journals PPN parameters in gravitational theory with nonminimally derivative coupling

2017 ◽  
Vol 26 (02) ◽  
pp. 1750005 ◽  
Author(s):  
Zhu Yi ◽  
Yungui Gong
Keyword(s):  
Scalar Field ◽  
Gravitational Theory ◽  
Kinetic Term ◽  
Nonminimal Coupling ◽  
Derivative Coupling ◽  
Tensor Theory ◽  
Experimental Constraint ◽  
Stress Energy ◽  
Ppn Parameters ◽  
Dynamical Dark Energy

The nonminimal coupling of the kinetic term to Einstein’s tensor helps the implementation of inflationary models due to the gravitationally enhanced friction. We calculate the parametrized post-Newtonian (PPN) parameters for the scalar–tensor theory of gravity with nonminimally derivative coupling. We find that under experimental constraint from the orbits of millisecond pulsars in our galaxy, the theory deviates from Einstein’s general relativity in the order of [Formula: see text], and the effect of the nonminimal coupling is negligible if we take the scalar field as dynamical dark energy. With the assumed conditions that the background scalar field is spatially homogeneous and evolves only on cosmological timescales and the contribution to stress–energy in the solar system from the background scalar field is subdominant, the scalar field is required to be massless.

scholarly journals Inflation driven by massive vector fields with derivative self-interactions

2019 ◽  
Vol 28 (04) ◽  
pp. 1950064 ◽  
Author(s):  
A. Oliveros ◽  
Marcos A. Jaraba
Keyword(s):  
Vector Field ◽  
Vector Fields ◽  
Kinetic Term ◽  
Model Parameters ◽  
Tensor Model ◽  
De Sitter ◽  
Frw Universe ◽  
Derivative Coupling ◽  
Massive Vector ◽  
Slow Roll

Inspired by the Generalized Proca Theory, we study a vector–tensor model of inflation with massive vector fields and derivative self-interactions. The action under consideration contains a usual Maxwell-like kinetic term, a general potential term and a term with nonminimal derivative coupling between the vector field and gravity, via the dual Riemann tensor. In this theory, the last term contains a free parameter, [Formula: see text], which quantifies the nonminimal derivative coupling. In this scenario, taking into account a spatially flat Friedmann–Robertson–Walker (FRW) universe and a general vector field, we obtain the general expressions for the equation of motion and the total energy–momentum tensor. Choosing a Proca-type potential, a suitable inflationary regimen driven by massive vector fields is studied. In this model, the isotropy of expansion is guaranteed by considering a triplet of orthogonal vector fields. In order to obtain an inflationary solution with this model, the quasi de Sitter expansion was considered. In this case, the vector field behaves as a constant. Finally, slow-roll analysis is performed and slow-roll conditions are defined for this model, which, for suitable constraints of the model parameters, can give the required number of e-folds for sufficient inflation.

scholarly journals NON-MINIMAL INFLATION ON THE RANDALL–SUNDRUM II BRANE WITH INDUCED GRAVITY

2009 ◽  
Vol 24 (39) ◽  
pp. 3205-3217 ◽  
Author(s):  
KOUROSH NOZARI ◽  
M. SHOUKRANI
Keyword(s):  
Scalar Curvature ◽  
Observational Data ◽  
Recent Observation ◽  
Model Parameters ◽  
Minimal Coupling ◽  
Induced Gravity ◽  
Inflaton Field ◽  
Inflation Model ◽  
Braneworld Model

We study an inflation model that inflaton field is non-minimally coupled to the scalar curvature on the Randall–Sundrum (RS) II brane. We investigate the effects of the non-minimal coupling on the inflationary dynamics of this braneworld model. Our study shows that the number of e-folds decreases by increasing the value of the conformal coupling. We compare our model parameters with the minimal case and also with recent observational data. In comparison with recent observation, we obtain a constraint on the values that conformal coupling attains.

scholarly journals Inflation with derivative self-interaction and coupling to gravity

2019 ◽  
Vol 79 (11) ◽  
Author(s):  
Gansukh Tumurtushaa
Keyword(s):  
Scalar Field ◽  
Observational Data ◽  
Power Spectra ◽  
Observational Constraints ◽  
Special Relation ◽  
Tensor Perturbation ◽  
Derivative Coupling ◽  
Inflaton Field ◽  
Cosmic Inflation ◽  
Single Term

Abstract We consider a subclass of Horndeski theories for studying cosmic inflation. In particular, we investigate models of inflation in which the derivative self-interaction of the scalar field and the non-minimal derivative coupling to gravity are present in the action and equally important during inflation. In order to control contributions of each term as well as to approach the single-term limit, we introduce a special relation between the derivative interaction and the coupling to gravity. By calculating observable quantities including the power spectra and spectral tilts of scalar and tensor perturbation modes, and the tensor-to-scalar ratio, we found that the tensor-to-scalar ratio is suppressed by a factor of $$(1+1/\gamma )$$(1+1/γ), where $$\gamma $$γ reflects the strength of the derivative self-interaction of the inflaton field with respect to the derivative coupling gravity. We placed observational constraints on the chaotic and natural inflation models and showed that the models are consistent with the current observational data mainly due to the suppressed tensor-to-scalar ratio.

EXPONENTIATED HALF-LOGISTIC LOMAX DISTRIBUTION WITH PROPERTIES AND APPLICATION

2019 ◽  
Vol XVI (2) ◽  
pp. 1-11
Author(s):  
Farrukh Jamal ◽  
Hesham Mohammed Reyad ◽  
Soha Othman Ahmed ◽  
Muhammad Akbar Ali Shah ◽  
Emrah Altun
Keyword(s):  
Real Data ◽  
Continuous Model ◽  
Model Parameters ◽  
Data Set ◽  
Lomax Distribution ◽  
Mathematical Properties ◽  
Proposed Model ◽  
Probability Weighted Moment ◽  
Record Statistics ◽  
Maximum Likelihood Criterion

A new three-parameter continuous model called the exponentiated half-logistic Lomax distribution is introduced in this paper. Basic mathematical properties for the proposed model were investigated which include raw and incomplete moments, skewness, kurtosis, generating functions, Rényi entropy, Lorenz, Bonferroni and Zenga curves, probability weighted moment, stress strength model, order statistics, and record statistics. The model parameters were estimated by using the maximum likelihood criterion and the behaviours of these estimates were examined by conducting a simulation study. The applicability of the new model is illustrated by applying it on a real data set.

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