Perturbation, non-Gaussianity, and reheating in a Gauss-Bonnet 
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-attractor model

Nozari, Kourosh; Rashidi, Narges

doi:10.1103/physrevd.95.123518

Cited by 84 publications

(46 citation statements)

References 98 publications

(142 reference statements)

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“…The Gauss-Bonnet term is a topological invariant quantity in four dimensions but may have dynamical relevance if coupled to an evolving scalar field. The Gauss-Bonnet term coupled to a scalar field arises naturally in the string theory [1] and uses in string inspired cosmological models [2,3,4,5,6,7], because have interesting cosmological implications both for early Universe [8,9,10,11,12,13,14,15] and for the late time dynamics [16,17,18,19,20,21] 1 .…”

Section: Introductionmentioning

confidence: 99%

Stability analysis of de Sitter solutions in models with the Gauss-Bonnet term

et al. 2019

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We investigate the scalar field dynamics of models with non-minimally coupled scalar fields in the presence of the Gauss-Bonnet term and derive the structure of effective potential and conditions for stable de Sitter solutions in general. Specializing to specific couplings, we explore the possibility of realizing the stable de Sitter configurations which may have implications for both the early Universe and late time evolution. * 1 Non-local cosmological models with the Gauss-Bonnet term are actively developed as well [22,23,24,25,26].

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Section: Introductionmentioning

confidence: 99%

Stability analysis of de Sitter solutions in models with the Gauss-Bonnet term

et al. 2019

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“…Therefore, in this work, we consider inflationary models with a Gauss-Bonnet (GB) term to estimate the energy spectrum of the PGW and to provide constraints on the reheating parameters. Inflationary models with a GB term are not uncommon, and it is well studied in the context of inflation, dark energy, and the PGW [28][29][30][31][32][33][34][35][36], as well as for reheating [37][38][39].…”

Section: Introductionmentioning

confidence: 99%

Constraints on the reheating parameters after Gauss-Bonnet inflation from primordial gravitational waves

2018

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We study the effects of the Gauss-Bonnet term on the energy spectrum of inflationary gravitational waves. The models of inflation are classified into two types based on their predictions for the tensor power spectrum: red-tilted (n T < 0) and blue-tilted spectra (n T > 0), respectively, and then the energy spectra of the gravitational waves are calculated for each type of model. We find that the gravitational wave spectra are enhanced depending on the model parameter if the predicted inflationary tensor spectra have a blue tilt, whereas they are suppressed for the spectra that have a red tilt. Moreover, we perform the analyses on the reheating parameters involving the temperature, the equation-of-state parameter, and the number of e-folds using the gravitational wave spectrum. Our results imply that the Gauss-Bonnet term plays an important role not only during inflation but also during reheating whether the process is instantaneous or lasts for a certain number of e-folds until it thermalizes and eventually completes. * Electronic address: kundol.koh@jejunu.ac.kr † Electronic address: bhl@sogang.ac.kr ‡ Electronic address: gansuhmgl@ibs.re.kr arXiv:1807.04424v2 [astro-ph.CO]

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“…In some extended models, there is some additional terms in consistency relation. In other words, in those cases, the consistency relation is modified [40,41,81,82,83]. As we said, the constraint on the tensor-to-scalar ratio, from Planck2018 TT, TE, EE+ lowEB + lensing data, is as r < 0.16 [66].…”

Section: Dbi Modelmentioning

confidence: 99%

Mimetic DBI Inflation in Confrontation with Planck2018 Data

Nozari

Rashidi

2019

ApJ

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We study mimetic gravity in the presence of a DBI-like term which is a non-canonical setup of the scalar field's derivatives. We consider two general cases with varying and constant sound speeds and construct the potentials for both the DBI and Mimetic DBI models. By considering the power-law scale factor as a = a 0 t n , we seek for the observational viability of these models. We show that, the Mimetic DBI model in some ranges of the parameters space is free of ghost and gradient instabilities. By studying r − n s and α s − n s behavior in confrontation with Planck2018 data, we find some constraints on the model's parameters. We show that for the case with varying sound speed, although power-law DBI inflation is not consistent with Planck2018 TT, TE, EE+low E+lensing data, but the Mimetic DBI inflation is consistent with Planck2018 TT, TE, EE+low E+lensing data at 95% CL, in some ranges of the model's parameters space as 40 ≤ n ≤ 55 where the model is instabilities-free in these ranges of parameters too. For the constant sound speed, by adopting some sample values of c s , we study both DBI and Mimetic DBI model numerically and find n ∼ 10 2 for DBI model and n ∼ 10 for Mimetic DBI model. We also compare the results with Planck2018 TT, TE, EE+low E+lensing+BK14+BAO data and see that the DBI and Mimetic DBI model with varying sound speed are ruled out with these joint data. However, these models with constant sound speed are consistent with Planck2018 TT, TE, EE+low E+lensing+BK14+BAO data with n ∼ 10 2 for DBI model and n ∼ 10 for Mimetic DBI model. In this case, we find some tighter constraints on the corresponding sound speed. PACS: 98.80. Bp, 98.80.Cq, 98.80.Es

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Perturbation, non-Gaussianity, and reheating in a Gauss-Bonnet α -attractor model

Cited by 84 publications

References 98 publications

Stability analysis of de Sitter solutions in models with the Gauss-Bonnet term

Stability analysis of de Sitter solutions in models with the Gauss-Bonnet term

Constraints on the reheating parameters after Gauss-Bonnet inflation from primordial gravitational waves

Mimetic DBI Inflation in Confrontation with Planck2018 Data

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