Tachyon-inspired viscous inflation using Hamilton–Jacobi’s formalism during high dissipative regime

2019 ◽  
Vol 28 (11) ◽  
pp. 1950136 ◽  
Author(s):  
Rabia Saleem
Keyword(s):  
Detailed Analysis ◽  
Model Parameters ◽  
Inflationary Model ◽  
Tachyon Field ◽  
Astrophysical Data ◽  
Slow Roll ◽  
Acceptable Range

This paper deals with warm viscous inflation inspired by tachyon field using an important inflationary method known as Hamilton–Jacobi’s Formalism. This method provides a way to solve the equations of inflationary model without using extra approximations other than slow-roll. In this scenario, a general inflationary formalism is developed for tachyon field and the work is restricted to high dissipative regime. A detailed analysis of the model is presented for three different cases of constant as well as variable bulk and dissipative coefficients. In each case, the model parameters are constrained to plot the physically acceptable range of the perturbed parameters. The parametric trajectories proved that the acquired results for all cases are compatible with Planck astrophysical data.

scholarly journals Induced gravity effect on inflationary parameters in a holographic cosmology

2020 ◽  
Vol 29 (02) ◽  
pp. 2050010 ◽  
Author(s):  
Aatifa Bargach ◽  
Farida Bargach ◽  
Ahmed Errahmani ◽  
Taoufik Ouali
Keyword(s):  
Model Parameters ◽  
Observational Constraints ◽  
Tachyon Field ◽  
Exponential Potential ◽  
Quadratic Potential ◽  
Induced Gravity ◽  
Slow Roll ◽  
Inflationary Parameters ◽  
Correction Terms ◽  
Good Agreement

We investigate the observational constraints on inflationary parameters in the context of a holographic cosmology with an induced gravity correction. We consider two situations where a universe is first filled with a scalar field and second with a tachyon field. Both cases are investigated in a slow-roll regime. We adopt a quadratic potential and an exponential potential for the scalar and the tachyon inflation, respectively. In this regard, the standard background and perturbative parameters characterizing the inflationary era are modified by correction terms. We show a good agreement between theoretical model parameters and Planck2018 observational data for both scalar and tachyon fields.

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.

Investigating inflation driven by DBI-essence scalar field

2020 ◽  
Vol 29 (12) ◽  
pp. 2050087
Author(s):  
Gargee Chakraborty ◽  
Surajit Chattopadhyay
Keyword(s):  
Scalar Field ◽  
Early Universe ◽  
Inflationary Model ◽  
Type Iii ◽  
Ultraviolet Cutoff ◽  
Big Rip ◽  
Slow Roll ◽  
Limiting Case

Motivated by the work of Nojiri et al., Phys. Lett. B 797, 134829 (2019), the present study demonstrates inflation driven by holographic DBI-essence scalar field. Considering a simple correction due to the Ultraviolet cutoff, we have studied the slow-roll parameters. It has been observed that the role of the UV-cutoff is not negligible and in the limiting case of [Formula: see text] the inflationary model is characterized by Type-III singularity but can avoid Big-Rip singularity. Finally, it has been observed that the trajectories in [Formula: see text] are compatible with the observational bound found by Planck. It has been concluded that the tensor to scalar ratio for this model can explain the primordial fluctuation in the early universe as well. However, under the purview of [Formula: see text] inflation, although the DBI-essence scalar field can explain primordial fluctuation, the holographic DBI-essence scalar field does not lead to [Formula: see text] trajectory satisfying the Planck’s observational bound.

scholarly journals Chameleon field dynamics during inflation

2018 ◽  
Vol 27 (04) ◽  
pp. 1850041 ◽  
Author(s):  
Nasim Saba ◽  
Mehrdad Farhoudi
Keyword(s):  
Scalar Field ◽  
Equation Of State ◽  
State Parameter ◽  
Big Bang ◽  
Late Time ◽  
Inflationary Model ◽  
Slow Roll ◽  
Equation Of State Parameter ◽  
The Common ◽  
The Universe

By studying the chameleon model during inflation, we investigate whether it can be a successful inflationary model, wherein we employ the common typical potential usually used in the literature. Thus, in the context of the slow-roll approximations, we obtain the e-folding number for the model to verify the ability of resolving the problems of standard big bang cosmology. Meanwhile, we apply the constraints on the form of the chosen potential and also on the equation of state parameter coupled to the scalar field. However, the results of the present analysis show that there is not much chance of having the chameleonic inflation. Hence, we suggest that if through some mechanism the chameleon model can be reduced to the standard inflationary model, then it may cover the whole era of the universe from the inflation up to the late time.

scholarly journals Asymptotic Solutions of a Generalized Starobinski Model: Kinetic Dominance, Slow Roll and Separatrices

Universe ◽  
2021 ◽  
Vol 7 (12) ◽  
pp. 500
Author(s):  
Elena Medina ◽  
Luis Martínez Alonso
Keyword(s):  
Asymptotic Expansions ◽  
Hubble Parameter ◽  
Initial Conditions ◽  
Asymptotic Solutions ◽  
Inflationary Model ◽  
Series Solutions ◽  
Fixed Amount ◽  
Inflaton Field ◽  
Slow Roll ◽  
Jacobi Formalism

We consider a generalized Starobinski inflationary model. We present a method for computing solutions as generalized asymptotic expansions, both in the kinetic dominance stage (psi series solutions) and in the slow roll stage (asymptotic expansions of the separatrix solutions). These asymptotic expansions are derived in the framework of the Hamilton-Jacobi formalism where the Hubble parameter is written as a function of the inflaton field. They are applied to determine the values of the inflaton field when the inflation period starts and ends as well as to estimate the corresponding amount of inflation. As a consequence, they can be used to select the appropriate initial conditions for determining a solution with a previously fixed amount of inflation.

scholarly journals KÄHLER MODULI INFLATION AND WMAP7

2011 ◽  
Vol 26 (06) ◽  
pp. 1073-1096 ◽  
Author(s):  
SUNGGEUN LEE ◽  
SOONKEON NAM
Keyword(s):  
Inflationary Model ◽  
Spectral Indices ◽  
Dimensional Problem ◽  
One Dimensional ◽  
Flux Compactification ◽  
Slow Roll ◽  
Wmap Data ◽  
Type Iib String Theory ◽  
Simple Potential

Inflationary potentials are investigated for specific models in type IIB string theory via flux compactification. As concrete models, we investigate several cases where the internal spaces are weighted projective spaces. The models we consider have two, three, or four Kähler moduli. The Kähler moduli play a role of inflaton fields and we consider the cases where only one of the moduli behaves as the inflaton field. For the cases with more than two moduli, we choose the diagonal basis for the expression of the Calabi–Yau volume, which can be written down as a function of four-cycle. With the combination of multiple moduli, we can express the multi-dimensional problem as an effective one-dimensional problem. In the large volume scenario, the potentials of these three models turn out to be of the same type. By taking the specific limit of the relation between the moduli and the volume, the potentials are reduced to simpler ones which induce inflation. For the case of two Kähler moduli, we exclude the potential as an inflationary model because the moduli might not be stable during inflation. As a toy model, we first consider the simple potential. We calculate the slow roll parameters ϵ, η and ξ for each inflationary potential. Then, we check whether the potentials give reasonable spectral indices ns and their running αs's by comparing with the recently released seven-year WMAP data. For both models, we see reasonable spectral indices for the number of e-folding 47<Ne<61. Conversely, by inserting the observed seven-year WMAP data, we see that the potential of the toy model gives requisite number of e-folds while the potential of the Kähler moduli gives much smaller number of e-folding. Finally, we see that two models do not produce reasonable values of the running of the spectral index.

scholarly journals DETAILED ANALYSIS OF p+p ELASTIC SCATTERING DATA IN THE QUARK–DIQUARK MODEL OF BIALAS AND BZDAK FROM $\sqrt{s} = 23.5~{\rm GeV}$ TO 7 TeV

2012 ◽  
Vol 27 (30) ◽  
pp. 1250175 ◽  
Author(s):  
F. NEMES ◽  
T. CSÖRGŐ
Keyword(s):  
Elastic Scattering ◽  
Energy Range ◽  
Detailed Analysis ◽  
Cross Section ◽  
Scattering Data ◽  
Model Parameters ◽  
Diquark Model ◽  
Proton Proton ◽  
Elastic Proton

Final results of a detailed analysis of p+p elastic scattering data are presented, utilizing the quark–diquark model of protons in a form proposed by Bialas and Bzdak. The differential cross-section of elastic proton–proton collisions is analyzed in a detailed and systematic manner at small momentum transfers, starting from the energy range of CERN ISR at [Formula: see text], including also recent TOTEM data at the present LHC energies at [Formula: see text]. These studies confirm the picture that the size of proton increases systematically with increasing energies, while the size of the constituent quarks and diquarks remains approximately independent of (or only increases slightly with) the colliding energy. The detailed analysis indicates correlations between model parameters and also indicates an increasing role of shadowing at LHC energies. Within the investigated class of models, a simple and model-independent phenomenological relation was discovered that connects the total p+p scattering cross-section to the effective quark, diquark size and their average separation. Our best fits indicate that the relative error of this phenomenological relation is 10–15% in the considered energy range.

scholarly journals Tachyonic inflation in loop quantum cosmology

2019 ◽  
Vol 79 (12) ◽  
Author(s):  
Kui Xiao
Keyword(s):  
Quantum Cosmology ◽  
Early Time ◽  
Field Energy ◽  
Loop Quantum Cosmology ◽  
Initial Condition ◽  
Tachyon Field ◽  
Slow Roll ◽  
Cosmological Inflation ◽  
Very High ◽  
Slow Roll Inflation

AbstractA tachyon field might be responsible for cosmological inflation at an early time and contribute to cosmological dark matter at a later time. We investigate tachyonic inflation by analyzing a tachyon field with different potentials in the framework of loop quantum cosmology. No matter which tachyon field energy dominates at the bounce, the evolution of the background can be divided into three phases: super-inflation, damping, and slow-roll inflation. The duration of each phase depends on the initial condition. During the slow-roll inflation, when the initial condition is $$V(T_\mathrm{B})/\rho _\mathrm{c}\ge 10^{-6}$$V(TB)/ρc≥10-6, the number of e-folds is very high ($$N\gg 60$$N≫60) for $$V\propto T^{-n}$$V∝T-n with $$n=1$$n=1 and 1 / 2. For an exponential potential, to get enough e-folds, $$V(T_\mathrm{B})/\rho _\mathrm{c}$$V(TB)/ρc should be greater than $$7.802\times 10^{-4}$$7.802×10-4. Furthermore, the probability of slow-roll inflation is obtained. We find that the probability of obtaining slow-roll inflation with 60 or more e-folds is very close to 1.

scholarly journals $$\alpha $$-attractor from superconformal E-models in brane inflation

2020 ◽  
Vol 80 (1) ◽  
Author(s):  
Mudassar Sabir ◽  
Waqas Ahmed ◽  
Yungui Gong ◽  
Yizhou Lu
Keyword(s):  
Friedmann Equation ◽  
High Energy ◽  
Model Parameters ◽  
Quadratic Term ◽  
Additional Parameter ◽  
Energy Limit ◽  
Brane Inflation ◽  
Slow Roll ◽  
Scalar Spectral Index ◽  
Braneworld Inflation

AbstractIn the large extra dimensional braneworld inflation, Friedmann equation is modified to include a quadratic term in energy density with an additional parameter $$\lambda $$λ called brane tension in addition to the usual linear term. The high energy brane corrections modify the slow-roll parameters and affect the behaviour of inflation. We analyse the superconformal inflation for E-models and find that there exist $$\alpha $$α-attractors in brane inflation. The predictions for the scalar spectral index $$n_s$$ns and the tensor-to-scalar ratio r are computed numerically, and approximate analytic formulas in the high energy limit have been given for the observable $$n_s$$ns and r. The constraints on the model parameters are obtained by using Planck 2018 and BICEP2 observational data.

scholarly journals General dissipative coefficient in warm intermediate inflation in Loop Quantum Cosmology in light of Planck and BICEP2

2014 ◽  
Vol 23 (10) ◽  
pp. 1450080 ◽  
Author(s):  
Ramón Herrera ◽  
Marco Olivares ◽  
Nelson Videla
Keyword(s):  
Quantum Cosmology ◽  
Loop Quantum Cosmology ◽  
Inflationary Model ◽  
Astronomical Observations ◽  
Hubble Rate ◽  
Slow Roll ◽  
Dissipative Coefficient ◽  
Perturbation Equations

In this paper, we study a warm intermediate inflationary model with a general form for the dissipative coefficient Γ(T, ϕ) = CϕTm/ϕm-1 in the context of Loop Quantum Cosmology (LQC). We examine this model in the weak and strong dissipative regimes. In general, we discuss in great detail the characteristics of this model in the slow-roll approximation. Also, we assume that the modifications to perturbation equations result exclusively from Hubble rate. In this approach, we use recent astronomical observations from Planck and BICEP2 experiments to restrict the parameters in our model.

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