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.

Braneworld mimetic f(R) gravity

2019 ◽  
Vol 16 (03) ◽  
pp. 1950042 ◽  
Author(s):  
Kourosh Nozari ◽  
Naser Sadeghnezhad
Keyword(s):  
Scalar Field ◽  
Recent Work ◽  
Friedmann Equation ◽  
Equation Of Motion ◽  
Einstein’S Field Equations ◽  
Field Equations ◽  
Einstein's Field Equations ◽  
Bulk Scalar Field ◽  
Codazzi Equations ◽  
Mimetic Gravity

Following our recent work on braneworld mimetic gravity, in this paper, we study an extension of braneworld mimetic gravity to the case that the gravitational sector on the brane is modified in the spirit of [Formula: see text] theories. We assume the physical 5D bulk metric in the Randall–Sundrum II braneworld scenario consists of a 5D scalar field (which mimics the dark sectors on the brane) and an auxiliary 5D metric. We find the 5D Einstein’s field equations and the 5D equation of motion of the bulk scalar field in this setup. By using the Gauss–Codazzi equations, we obtain the induced Einstein’s field equations on the brane. Finally, by adopting the FRW background, we find the Friedmann equation on the brane in this [Formula: see text] mimetic braneworld setup.

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 STABLE TWO-BRANE MODELS WITH BULK TACHYON MATTER

2009 ◽  
Vol 24 (24) ◽  
pp. 4457-4471 ◽  
Author(s):  
A. DAS ◽  
SAYAN KAR ◽  
SOUMITRA SENGUPTA
Keyword(s):  
Stability Analysis ◽  
Scalar Field ◽  
Source Term ◽  
Warp Factor ◽  
Hierarchy Problem ◽  
Bulk Scalar Field ◽  
Brane Models

We explore the possibility of constructing stable, warped two-brane models which solve the hierarchy problem, with a bulk noncanonical scalar field (tachyon matter) as the source term in the action. Among our examples are two models — one with a warp factor (denoted as e-2f(σ)) which differs from that of the standard Randall–Sundrum by the addition of a quadratic piece in the f(σ) and another, where the warping is superexponential. We investigate the issue of resolution of hierarchy and perform a stability analysis by obtaining the effective interbrane potentials, in each case. Our analysis reveals that there does exist stable values of the modulus consistent with hierarchy resolution in both the models. Thus, these models, in which the bulk scalar field generates the geometry and also ensures stability, provide viable alternatives to the standard Randall–Sundrum two-brane scenario.

scholarly journals Interacting dark energy model in the brane scenario: A dynamical system analysis

2019 ◽  
Vol 16 (08) ◽  
pp. 1950115
Author(s):  
Sujay Kr. Biswas ◽  
Subenoy Chakraborty
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Scalar Field ◽  
Critical Points ◽  
System Analysis ◽  
Evolution Equations ◽  
Field Potential ◽  
Brane Cosmology ◽  
Brane Model ◽  
Barotropic Equation

The present work is a second in the series of investigations of the background dynamics in brane cosmology when dark energy is coupled to dark matter by a suitable interaction. Here, dark matter is chosen in the form of perfect fluid with barotropic equation of state, while a real scalar field with self-interacting potential is chosen as dark energy. The scalar field potential is chosen as exponential or hyperbolic in nature and three different choices for the interactions between the dark species are considered. In the background of spatially flat, homogeneous and isotropic Friedmann–Robertson–Walker (FRW) brane model, the evolution equations are reduced to an autonomous system by suitable transformation of variables and a series of critical points are obtained for different interactions. By analyzing the critical points, we have found a cosmologically viable model describing an early inflationary scenario to dark energy-dominated era connecting through a matter-dominated phase.

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 WARPED GEOMETRY OF BRANE WORLDS

2002 ◽  
Vol 17 (29) ◽  
pp. 4297-4305 ◽  
Author(s):  
GARY FELDER
Keyword(s):  
Scalar Field ◽  
Three Dimensional ◽  
Field Potential ◽  
Brane World ◽  
Phase Portraits ◽  
Warp Factor ◽  
De Sitter ◽  
Dynamical Equations ◽  
Dimensional Dependence ◽  
Finite Distance

We study the dynamical equations for extra-dimensional dependence of a warp factor and a bulk scalar in 5D brane world scenarios with 3+1 de Sitter slices. We show that these equations are similar to the equations for 4D scalar field cosmology, but with the sign of the scalar field potential reversed. We construct three dimensional phase portraits for this system for a variety of potentials. We show that for many potentials there will be an unavoidable singularity occuring a finite distance from the brane. This singularity can be shielded by the addition of a second brane. The properties of these branes will generally fix the inter-brane separation and effective 4D cosmological constants, thus providing a possible mechanism for stabilizing the braneworld. Some of these results were previously known for some models, but we bring together a variety of results and show how they can all be easily seen using phase portraits.

Exact inflationary solution in the chaotic inflation model to non-minimally coupled scalar field

2009 ◽  
Vol 87 (11) ◽  
pp. 1181-1184
Author(s):  
Shiwu Chen ◽  
Xizhun Hao ◽  
Xiongwei Liu ◽  
Shuzheng Yang
Keyword(s):  
Scalar Field ◽  
Spectral Index ◽  
Hubble Parameter ◽  
Density Fluctuation ◽  
Minimal Coupling ◽  
Astronomical Observations ◽  
Scalar Density ◽  
Inflation Model ◽  
Exact Inflationary Solution ◽  
Chaotic Inflation

We present a new exact inflationary solution for the chaotic inflation model with non-minimal coupling, by taking the Hubble parameter directly as a function of a scalar field. We then prove that the spectral index of the scalar density fluctuation (and other parameters), which derived from the exact inflationary solution, is exactly consistent with recent astronomical observations.

scholarly journals BRANE COSMOLOGY WITH A BULK SCALAR FIELD

2002 ◽  
Vol 17 (20) ◽  
pp. 2774-2774
Author(s):  
M. RODRÍGUEZ-MARTÍNEZ
Keyword(s):  
Scalar Field ◽  
Friedmann Equation ◽  
Analytic Solutions ◽  
Scale Factor ◽  
Cosmological Evolution ◽  
World Sheet ◽  
Brane Cosmology ◽  
Static Solutions ◽  
Bulk Scalar Field ◽  
Bulk Scale

In the last few years, brane cosmological models with extra dimensions have been actively studied. In these scenarios, ordinary matter is confined in a (3+1)-dimensional surface (the world-sheet of a 3-brane) while gravity lives in the bulk space-time2,3. In this regard, it has been shown that the cosmology of such models is characterized by a non standard Friedmann equation4,5. Some analytic solutions have been found when the scalar field couples to the brane6, but they correspond to static solutions where the cosmological evolution is due to the motion of the brane into the bulk. In this talk I have presented two kinds of exact solutions obtained by solving Einstein's equations in the light-cone coordinate system and making two different assumptions : a. proportionality between the scalar field and the logarithm of the bulk scale factor7 and b. separable solutions. It has been shown that the first kind of solutions correspond to moving branes into static backgrounds : somehow the hypothesis of proportionality froze the evolution of the metric. On the contrary, in the second kind of solution the bulk is really dynamic. The induced cosmology in the brane has been explored for both types of solutions, confirming, in particular, the non standard cosmological evolution of the scale factor.

BULK SCALAR-FIELD INFLUENCED FRW UNIVERSE MODEL

2012 ◽  
Vol 27 (01) ◽  
pp. 1250003 ◽  
Author(s):  
TAE HOON LEE ◽  
SUNNYEO LEE
Keyword(s):  
Sigma Model ◽  
Scalar Fields ◽  
Einstein Gravity ◽  
Warp Factor ◽  
Nonlinear Sigma Model ◽  
Universe Model ◽  
Frw Universe ◽  
Brane Model ◽  
Bulk Scalar Field ◽  
The One

We consider a nonlinear sigma-model-like theory of bulk scalar fields coupled to the five-dimensional Einstein gravity. In Robertson–Walker spacetimes, we find some power-law cosmological solutions for the scale factor when the expansion rate of an extra dimension is proportional to one of our (3+1)-dimensional universe. Among them, the solution with a decreasing warp factor could be related to the one-brane model of Randall and Sundrum.

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