Inflation with Gauss-Bonnet coupling

Zhu, Yanjun; Gong, Yungui; Sabir, Mudassar

doi:10.1103/physrevd.98.083521

Cited by 76 publications

(37 citation statements)

References 72 publications

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“…Now we discuss the first swampland criterion SCI for the field excursion. The Lyth bound tells us that [14,39] ∆φ > ∆N…”

Section: The Gauss-bonnet Inflationmentioning

confidence: 99%

“…In Ref. [39], we find a powerful mechanism to reduce the tensor to scalar ratio r. With the help of the Gauss-Bonnet term, for any potential, the tensor to scalar r is reduced by a factor 1 − λ with the order 1 parameter λ, which may possibly solve the swampland problem. Generally, the predictions of the inflation, n s and r, are calculated under the slow-roll condition, (V /V ) 2 1.…”

Section: Introductionmentioning

confidence: 99%

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Gauss–Bonnet Inflation and the String Swampland

Zhu

Gong

2019

Universe

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The two swampland criteria are generically in tension with the single field slow-roll inflation because the first swampland criterion requires small tensor to scalar ratio while the second swampland criterion requires large tensor to scalar ratio. The challenge to the single field slow-roll inflation imposed by the swampland criteria can be avoided by modifying the relationship between the tensor to scalar ratio and the slow-roll parameter. We show that the Gauss-Bonnet inflation with the coupling function inversely proportional to the potential overcomes the challenge by adding a constant factor in the relationship between the tensor to scalar ratio and the slow-roll parameter.For the Gauss-Bonnet inflation, while the swampland criteria are satisfied, the slow-roll conditions are also fulfilled, so the scalar spectral tilt and the tensor to scalar ratio are consistent with the observations. We use the potentials for chaotic inflation and the E-model as examples to show that the models pass all the constraints. The swampland criteria may imply Gauss-Bonnet coupling.

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“…Now we discuss the first swampland criterion SCI for the field excursion. The Lyth bound tells us that [14,39] ∆φ > ∆N…”

Section: The Gauss-bonnet Inflationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Gauss–Bonnet Inflation and the String Swampland

Zhu

Gong

2019

Universe

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“…As we already mentioned, the ghost-free f (G) model of Eq. (4) is a sort of scalar Einstein-Gauss-Bonnet model [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38][39], the cosmological perturbations of which were studied in Ref. [40].…”

Section: Inflationary Dynamics Of the Ghost-free F (G) Modelmentioning

confidence: 99%

Viable inflationary models in a ghost-free Gauss–Bonnet theory of gravity

et al. 2019

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In this work we investigate the inflationary phenomenological implications of a recently developed ghostfree Gauss-Bonnet theory of gravity. The resulting theory can be viewed as a scalar Einstein-Gauss-Bonnet theory of gravity, so by employing the formalism for cosmological perturbations for the latter theory, we calculate the slowroll indices and the observational indices, and we compare these with the latest observational data. Due to the presence of a freely chosen function in the model, in principle any cosmological evolution can be realized, so we specify the Hubble rate and the freely chosen function and we examine the phenomenology of the model. Specifically we focus on de Sitter, quasi-de Sitter and a cosmological evolution in which the Hubble rate evolves exponentially, with the last two being more realistic choices for describing inflation. As we demonstrate, the ghost-free model can produce inflationary phenomenology compatible with the observational data. We also briefly address the stability of first order scalar and tensor cosmological perturbations, for the exponential Hubble rate, and as we demonstrate, stability is achieved for the same range of values of the free parameters that guarantee the phenomenological viability of the models.

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“…Such a e-mail: tjgao@xidian.edu.cn (corresponding author) class of models can also produce a scale-invariant spectrum and is compatible with the observational constraints without the assumption of slow-roll approximation. The constantroll condition with small η H is compatible with the slow-roll inflation, and a special value η H = 3 amounts to the ultraslow-roll inflation [4,5], in which the potential is very flat and the inflaton almost stops rolling.The constant-roll inflationary models are discussed in more details in [6][7][8], and extended to modified theories of gravity [9][10][11][12][13][14] or two fields case [15], and using other constant-roll conditions [16][17][18]. Other developments are appeared in [19][20][21][22].…”

Section: Introductionmentioning

confidence: 99%

Gauss–Bonnet inflation with a constant rate of roll

Gao

2020

Eur. Phys. J. C

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In the model of the inflaton nonminimal coupling to the Gauss–Bonnet term, we discuss the constant-roll inflation with constant $$\epsilon _1$$ ϵ 1 , constant $$\epsilon _2$$ ϵ 2 and constant $$\eta _H$$ η H , respectively, with the additional assumption that $$\delta _1$$ δ 1 is a constant. Using the Bessel function approximation, we get the analytical expressions for the scalar and tensor power spectrum and derive the scalar spectral index $$n_{\mathcal {R}}$$ n R and the tensor to scalar ratio r to the first order of $$\epsilon _1$$ ϵ 1 . By using the Planck 2018 observations constraint on $$n_{\mathcal {R}}$$ n R and r, we obtain some feasible parameter space and show the result on the $$n_{\mathcal {R}}-r$$ n R - r region. The scalar potential is also reconstructed in some special cases.

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Inflation with Gauss-Bonnet coupling

Cited by 76 publications

References 72 publications

Gauss–Bonnet Inflation and the String Swampland

Gauss–Bonnet Inflation and the String Swampland

Viable inflationary models in a ghost-free Gauss–Bonnet theory of gravity

Gauss–Bonnet inflation with a constant rate of roll

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