scholarly journals Warm constant-roll inflation in brane-world cosmology

2021 ◽  
Author(s):  
M. R. Setare ◽  
A. Ravanpak ◽  
K. Bahari ◽  
G. F. Fadakar
Keyword(s):  
Scalar Field ◽  
Analytical Solution ◽  
Friedmann Equation ◽  
Equation Of Motion ◽  
Brane World ◽  
Inflationary Model ◽  
Warm Inflation ◽  
Scalar Spectral Index ◽  
Good Consistency ◽  
Numerical Approaches

In this paper, we study a constant-roll inflationary model in the context of brane-world cosmology caused by a quintessence scalar field for warm inflation with a constant dissipative parameter [Formula: see text]. We determine the analytical solution for the Friedmann equation coupled to the equation of motion of the scalar field. The evolution of the primordial scalar and tensor perturbations is also studied using the modified Langevin equation. To check the viability of the model, we use numerical approaches and plot some figures. Our results for the scalar spectral index and the tensor-to-scalar ratio show good consistency with 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 α-Attractors and reheating in a nonminimal inflationary model

2020 ◽  
Vol 29 (10) ◽  
pp. 2050077
Author(s):  
R. Shojaee ◽  
K. Nozari ◽  
F. Darabi
Keyword(s):  
Scalar Field ◽  
Spectral Index ◽  
Parameter Space ◽  
Model Potential ◽  
Index Formula ◽  
Inflationary Model ◽  
Scalar Spectral Index ◽  
Canonical Scalar Field

We study [Formula: see text]-attractor models with both E-model and T-model potential in an extended Nonminimal Derivative (NMD) inflation where a canonical scalar field and its derivatives are nonminimally coupled to gravity. We calculate the evolution of perturbations during this regime. Then by adopting inflation potentials of the model we show that in the large [Formula: see text] and small [Formula: see text] limit, the value of the scalar spectral index [Formula: see text] and tensor-to-scalar ratio [Formula: see text] are universal. Next, we study reheating after inflation in this formalism. We obtain some constraints on the model’s parameter space by adopting the results with Planck 2018.

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.

scholarly journals IMPLEMENTING POWER LAW INFLATION WITH TACHYON ROLLING ON THE BRANE

2003 ◽  
Vol 18 (10) ◽  
pp. 691-697 ◽  
Author(s):  
M. SAMI
Keyword(s):  
Scalar Field ◽  
Power Law ◽  
Ground State ◽  
Friedmann Equation ◽  
Brane World ◽  
Tachyon Field

We study a minimally coupled tachyon field rolling down to its ground state on the FRW brane. We construct tachyonic potential which can implement power law inflation in the brane world cosmology. The potential turns out to be V0ϕ-1 on the brane and reduces to inverse square potential at late times when brane corrections to the Friedmann equation become negligible. We also do similar exercise with a normal scalar field and discover that the inverse square potential on the brane leads to power law inflation.

Scalar field thin shell collapse in the Brane-world geometry

2020 ◽  
Vol 35 (06) ◽  
pp. 2050028
Author(s):  
G. Abbas ◽  
M. R. Shahzad
Keyword(s):  
Black Hole ◽  
Scalar Field ◽  
Effective Potential ◽  
Thin Shell ◽  
Quadratic Function ◽  
Equation Of Motion ◽  
Brane World ◽  
Massive Scalar ◽  
Dynamical Equations ◽  
Massive Scalar Field

In this paper, we studied the dynamics of thin shell in the perfect fluid composed of scalar field. To formulate the equation of motion of the shell, we used the Israel thin-shell formalism for the Brane-world black hole in the two surrounding vacuum regions (interior and exterior). In this study, we considered the potential function as a quadratic function of scalar field. The resulting dynamical equations have been analyzed numerically for both the cases, massless and massive scalar field through the effective potential and radius of the shell by considering different settings of the parameters involved. We found that there are three possibilities in this geometry, thin shell in the scalar field can expand, collapse or attain equilibrium for a while, however, in most of the cases for large value of radius, thin shell collapses to zero size. The effects of the parameters [Formula: see text] and [Formula: see text] (involved due to the Brane-world geometry) on the expansion and collapsing rates have been analyzed and the obtained results compared with the Schwarzschild case ([Formula: see text], [Formula: see text]).

scholarly journals A New Solution of Intermediate Cosmological Inflation with the Effect of Scalar Field

2021 ◽  
Vol 41 (1) ◽  
pp. 112-121
Author(s):  
Shomi Aktar ◽  
Anjan Kumar Chowdhury
Keyword(s):  
Scalar Field ◽  
Power Law ◽  
Equation Of Motion ◽  
Rapid Expansion ◽  
Inflationary Universe ◽  
Inflationary Model ◽  
Cosmological Inflation ◽  
The Universe ◽  
Interior Solutions

According to the inflationary model, the universe had a brief period of extraordinarily rapid expansion or inflation during which its diameter increased by a factor at least 1025 times larger than previously thought. In this work an analysis is given on inflationary universe, which expands at a rate intermediate between that of power-law and exponential inflation. We have examined the model of Barrow which is solved exactly and leaded to power law inflation. We have tested a new potential by applying the scalar field using the equation of motion and found some new interior solutions. The Chittagong Univ. J. Sci. 40(1) : 112-121, 2019

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 SELF-TUNING DARK ENERGY IN BRANE WORLD COSMOLOGY

2001 ◽  
Vol 16 (17) ◽  
pp. 1089-1099 ◽  
Author(s):  
KUNIHITO UZAWA ◽  
JIRO SODA
Keyword(s):  
Dark Energy ◽  
Scalar Field ◽  
Vacuum Energy ◽  
Friedmann Equation ◽  
Brane World ◽  
Tuning Mechanism ◽  
Enormous Amount ◽  
Self Tuning ◽  
Bulk Scalar Field

In this letter, the self-tuning mechanism of dark energy is proposed by considering the cosmological matter in the brane world. In the first part of this letter, the effective four-dimensional Friedmann equation in the presence of the bulk scalar field is derived. In our model, the bulk scalar field takes the role of the dark energy and its value is slowly varying in time. The claim is that, even if the enormous amount of vacuum energy exists on the brane, the present value of the dark energy is self-tuned to be consistent with the current observations. This result will open the possibility to discuss the dark energy in the brane world in the context of the anthropic principle or quantum cosmology.

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 FERMIONIC AND SCALAR FIELDS AS SOURCES OF INTERACTING DARK MATTER–DARK ENERGY

2011 ◽  
Vol 20 (13) ◽  
pp. 2543-2558 ◽  
Author(s):  
SAMUEL LEPE ◽  
JAVIER LORCA ◽  
FRANCISCO PEÑA ◽  
YERKO VÁSQUEZ
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Scalar Field ◽  
Analytical Solution ◽  
Scalar Fields ◽  
Nonminimal Coupling ◽  
Field Equations ◽  
Fermionic Field ◽  
Minimal Coupling ◽  
Constant Type

From a variational action with nonminimal coupling with a scalar field and classical scalar and fermionic interaction, cosmological field equations can be obtained. Imposing a Friedmann–Lemaître–Robertson–Walker (FLRW) metric, the equations lead directly to a cosmological model consisting of two interacting fluids, where the scalar field fluid is interpreted as dark energy and the fermionic field fluid is interpreted as dark matter. Several cases were studied analytically and numerically. An important feature of the non-minimal coupling is that it allows crossing the barrier from a quintessence to phantom behavior. The insensitivity of the solutions to one of the parameters of the model permits it to find an almost analytical solution for the cosmological constant type of universe.

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