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 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.

CONFORMAL COUPLING'S OUTRAGEOUS LEGACY

2002 ◽  
Vol 11 (10) ◽  
pp. 1531-1536
Author(s):  
L. RAUL ABRAMO ◽  
LEON BRENIG ◽  
EDGARD GUNZIG
Keyword(s):  
Scalar Field ◽  
Scalar Curvature ◽  
The Other ◽  
Minimal Coupling ◽  
Quantum Stability ◽  
Paradoxical Situation ◽  
Other Hand ◽  
The One ◽  
Hilbert Action ◽  
Scalar Gravity

In Einstein's gravity, non-minimal coupling of a scalar field to the scalar curvature leads to a paradoxical situation. On the one hand, it opens the way to qualitatively new cosmological dynamics. On the other hand, there are sectors of non-minimally coupled scalar-gravity theories for which the Einstein–Hilbert action reverses its sign, which seems to indicate that the whole system is unstable. We show how conformal coupling bypasses this problem. Due to a subtle interplay between gravity and the scalar field, classical and quantum stability are guaranteed globally. This liberates conformal coupling from a serious obstacle. Inflationary solutions in the new sector are also presented, which are validated by current observations.

scholarly journals Numerical Modelling of Salt-Related Stress Decoupling in Sedimentary Basins–Motivated by Observational Data from the North German Basin

Geosciences ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 19
Author(s):  
Steffen Ahlers ◽  
Tobias Hergert ◽  
Andreas Henk
Keyword(s):  
Observational Data ◽  
Sedimentary Cover ◽  
Sedimentary Basins ◽  
Stress Fields ◽  
Salt Diapir ◽  
Model Parameters ◽  
Salt Layer ◽  
Stress Changes ◽  
Stress Orientations ◽  
Mechanical Decoupling

A three dimensional (3D) finite element model is used to study the conditions leading to mechanical decoupling at a salt layer and vertically varying stress fields in salt-bearing sedimentary basins. The study was inspired by observational data from northern Germany showing stress orientations varying up to 90° between the subsalt and the suprasalt layers. Parameter studies address the role of salt viscosity and salt topology on how the plate boundary forces acting at the basement level affect the stresses in the sedimentary cover above the salt layer. Modelling results indicate that mechanical decoupling occurs for dynamic salt viscosities lower than 1021 Pa·s, albeit this value depends on the assumed model parameters. In this case, two independent stress fields coexist above and below the salt layer, differing in tectonic stress regime and/or stress orientation. Thereby, stresses in the subsalt domain are dominated by the shortening applied, whereas in the suprasalt section they are controlled by the local salt topology. For a salt diapir, the orientation of the maximum horizontal stress changes from a circular pattern above to a radial pattern adjacent to the diapir. The study shows the value of geomechanical models for stress prediction in salt-bearing sedimentary basins providing a continuum mechanics–based explanation for the variable stress orientations observed.

scholarly journals CMB ANISOTROPIES REVEAL QUANTIZED GRAVITY

2005 ◽  
Vol 20 (07) ◽  
pp. 509-517 ◽  
Author(s):  
KEN-JI HAMADA ◽  
TETSUYUKI YUKAWA
Keyword(s):  
Quantum Gravity ◽  
Scalar Curvature ◽  
Early Universe ◽  
Time Constant ◽  
Power Spectra ◽  
Induced Gravity ◽  
Sharp Fall ◽  
Conformal Field ◽  
Expansion Time ◽  
Renormalizable Model

A novel primordial spectrum with a dynamical scale of quantum gravity origin is proposed to explain the sharp fall off of the angular power spectra at low multipoles in the COBE and WMAP observations. The spectrum is derived from quantum fluctuations of the scalar curvature in a renormalizable model of induced gravity. This model describes the very early universe by the conformal field fluctuating about an inflationary background with the expansion time constant of order of the Planck mass.

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 THE EFFECT OF DIFFERENT OBSERVATIONAL DATA IN CONSTRAINING COSMOLOGICAL PARAMETERS

2012 ◽  
Vol 10 ◽  
pp. 85-94 ◽  
Author(s):  
YUNGUI GONG ◽  
QING GAO ◽  
ZONG-HONG ZHU
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Observational Data ◽  
Cosmological Parameters ◽  
State Parameter ◽  
Wilkinson Microwave Anisotropy Probe ◽  
Model Parameters ◽  
Type Ia Supernova ◽  
Equation Of State Parameter ◽  
Type Ia

We use the SNLS3 compilation of 472 type Ia supernova data, the baryon acoustic oscillation measurement of distance, and the cosmic microwave background radiation data from the seven year Wilkinson Microwave Anisotropy Probe to study the effect of their different combinations on the fittings of cosmological parameters. Neither BAO nor WMAP7 data alone gives good constraint on the equation of state parameter of dark energy, but both WMAP7 data and BAO data help type Ia supernova data break the degeneracies among the model parameters, hence tighten the constraint on the variation of equation of state parameter wa, and WMAP7 data does the job a little better. Although BAO and WMAP7 data provide reasonably good constraints on Ωm and Ωk, it is not able to constrain the dynamics of dark energy, we need SNe Ia data to probe the property of dark energy, especially the variation of the equation of state parameter of dark energy. For the SNLS SNe Ia data, the nuisance parameters α and β are consistent for all different combinations of the above data. Their impacts on the fittings of cosmological parameters are minimal. ΛCDM model is consistent with current observational data.

scholarly journals HIGGS INFLATION IN f(Φ, R) THEORY

2014 ◽  
Vol 23 (04) ◽  
pp. 1450029 ◽  
Author(s):  
GIRISH KUMAR CHAKRAVARTY ◽  
SUBHENDRA MOHANTY ◽  
NAVEEN K. SINGH
Keyword(s):  
Scalar Curvature ◽  
Spectral Index ◽  
Early Universe ◽  
Coupling Parameter ◽  
Planck Scale ◽  
Higgs Field ◽  
Coupling Model ◽  
Order Unity ◽  
Inflation Model ◽  
Higher Dimensional

We generalize the scalar-curvature coupling model ξΦ2R of Higgs inflation to ξΦaRb to study inflation. We compute the amplitude and spectral index of curvature perturbations generated during inflation and fix the parameters of the model by comparing these with the Planck + WP data. We find that if the scalar self-coupling λ is in the range 10-5–0.1, parameter a in the range 2.3–3.6 and b in the range 0.77–0.22 at the Planck scale, one can have a viable inflation model even for ξ ≃ 1. The tensor to scalar ratio r in this model is small and our model with scalar-curvature couplings is not ruled out by observational limits on r unlike the pure [Formula: see text] theory. By requiring the curvature coupling parameter to be of order unity, we have evaded the problem of unitarity violation in scalar-graviton scatterings which plague the ξΦ2R Higgs inflation models. We conclude that the Higgs field may still be a good candidate for being the inflaton in the early universe if one considers higher-dimensional curvature coupling.

Cosmological inflation in a generalized unimodular gravity

2017 ◽  
Vol 26 (10) ◽  
pp. 1750107 ◽  
Author(s):  
K. Nozari ◽  
S. Shafizadeh
Keyword(s):  
Observational Data ◽  
Einstein Frame ◽  
Model Parameters ◽  
Type Formula ◽  
Cosmological Inflation

We study some aspects of cosmological inflation in the framework of unimodular [Formula: see text] gravity. To be more clearer, we consider a generic [Formula: see text] of the type [Formula: see text]. By considering the Einstein frame counterpart of the unimodular [Formula: see text] gravity, we set the scalaron to be responsible for cosmological inflation in this setup. We confront our model parameters space with observational data and impose some constraints on the value of [Formula: see text] in this manner. We show that for the number of [Formula: see text]-folds [Formula: see text], the model is consistent with observation if [Formula: see text].

New constraint of an attractor GL model in braneworld context

2017 ◽  
Vol 32 (19n20) ◽  
pp. 1750119
Author(s):  
Z. Mounzi ◽  
A. Safsafi ◽  
M. Ferricha-Alami ◽  
M. Bennai
Keyword(s):  
Power Spectrum ◽  
Spectral Index ◽  
Index Formula ◽  
Brane Tension ◽  
Inflation Model ◽  
Scalar Spectral Index ◽  
Central Value ◽  
Braneworld Model ◽  
Inflationary Parameters

We are interested in studying the generalization of the first chaotic inflation model in supergravity, which was proposed by Goncharov and Linde (GL model) and was recently revisited, in the framework of the Randall–Sundrum type 2 braneworld model. This model predicts a tiny ratio [Formula: see text] and [Formula: see text]. Our scenario predicts a great tensor-to-scalar ratio [Formula: see text] of the order [Formula: see text] and the central value of the scalar spectral index [Formula: see text] for a particular choice of values of brane tension [Formula: see text] and the parameter [Formula: see text]. We have shown that this scenario reproduces successfully an attractor behavior. We have also derived all known spectrum inflationary parameters, in particular the running [Formula: see text] and the power spectrum of the curvature perturbations [Formula: see text] which are widely consistent with Planck observations.

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