De Sitter Solutions in Einstein–Gauss–Bonnet Gravity

Vernov, S. Yu.; Pozdeeva, Ekaterina

doi:10.3390/universe7050149

Cited by 25 publications

(9 citation statements)

References 72 publications

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“…(28). A direct comparison of the final expressions for the slow-roll indices ( 22)-( 27), and of the tensor spectral index (34) and the tensor-to-scalar ratio (33), with the expressions obtained in Ref. [17], can show the simplicity of the expressions obtained in the present work.…”

Section: Simplified Einstein-gauss-bonnet Inflation Frameworksupporting

confidence: 62%

“…[17], with φ f being the value of the scalar field at the end of the inflationary era, and φ i is the value of the scalar field at the beginning of the inflationary era, precisely at the first horizon crossing time instance. Essentially, the slow-roll indices ( 22)-( 27), the tensor spectral index (34) and the tensor-to-scalar ratio (33) are the main results of this work. We shall use this simplified framework to examine whether a viable phenomenology can be obtained.…”

Section: Simplified Einstein-gauss-bonnet Inflation Frameworkmentioning

confidence: 98%

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A Refined Einstein-Gauss-Bonnet Inflationary Theoretical Framework

Oikonomou

2021

Preprint

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We provide a refined and much more simplified Einstein-Gauss-Bonnet inflationary theoretical framework, which is compatible with the GW170817 observational constraints on the gravitational wave speed. As in previous works, the constraint that the gravitational wave speed is c 2 T = 1 in natural units, results to a constraint differential equation that relates the coupling function of the scalar field to the Gauss-Bonnet invariant ξ(φ) and the scalar potential V (φ). Adopting the slow-roll conditions for the scalar field and the Hubble rate, and in contrast to previous works, by further assuming that κ ξ ξ 1, which is motivated by slow-roll arguments, we succeed in providing much more simpler expressions for the slow-roll indices and for the tensor and scalar spectral indices and for the tensor-to-scalar ratio. We exemplify our refined theoretical framework by using an illustrative example with a simple power-law scalar coupling function ξ(φ) ∼ φ ν and as we demonstrate the resulting inflationary phenomenology is compatible with the latest Planck data. Moreover, this particular model produces a blue-tilted tensor spectral index, so we discuss in brief the perspective of describing the NANOGrav result with this model as is indicated in the recent literature.

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Section: Simplified Einstein-gauss-bonnet Inflation Frameworksupporting

confidence: 62%

Section: Simplified Einstein-gauss-bonnet Inflation Frameworkmentioning

confidence: 98%

A Refined Einstein-Gauss-Bonnet Inflationary Theoretical Framework

Oikonomou

2021

Preprint

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“…The case of an exponential potential and r ∼ (N e + N 0 ) −2 was considered in [54,59]. Now, we consider the case of the exponential potential and r ∼ (N + N 0 ) −1 :…”

Section: Exponential Effective Potentialmentioning

confidence: 99%

“…In the present paper, models without the introduction of V(φ) and ξ(φ) leading to inflationary parameters of cosmological attractors with r ∼ (N e + N 0 ) −1 are considered. In our consideration, the effective potential formulated for Einstein-Gauss-Bonnet gravity [58] applicable near de Sitter solution [59] or in slow-roll regime [31,55] is used.…”

Section: Introductionmentioning

confidence: 99%

Deviation from Slow-Roll Regime in the EGB Inflationary Models with r ∼ Ne−1

Pozdeeva

2021

Universe

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We consider Einstein–Gauss–Bonnet (EGB) inflationary models using the effective potential approach. We present evolution equations in the slow-roll regime using the effective potential and the tensor-to-scalar ratio. The choice of the effective potential is related to an expression of the spectral index in terms of e-folding number Ne. The satisfaction of the slow-roll regime is mostly related to the form of the tensor-to-scalar ratio r. The case of r∼1/Ne2 leads to a generalization of α-attractors inflationary parameters to Einstein–Gauss–Bonnet gravity with exponential effective potential. Moreover, the cosmological attractors include models with r∼1/Ne. And we check the satisfaction of the slow-roll regime during inflation for models with r∼1/Ne.

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“…For a given proposed dark energy mode model, there are systematic methods for the investigation of the physical properties of the model. The derivation of exact and analytic solutions is an essential approach because analytic techniques can be used for the investigation of the cosmological viability of the model [17][18][19][20]. Furthermore, from the analysis of the asymptotic dynamics, that is, of the determination of the stationary points, the complete cosmological history can be constructed [21][22][23].…”

Section: Introductionmentioning

confidence: 99%

Dynamical Analysis and Cosmological Evolution in Weyl Integrable Gravity

Paliathanasis

2021

Universe

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We investigate the cosmological evolution for the physical parameters in Weyl integrable gravity in a Friedmann–Lemaître–Robertson–Walker universe with zero spatial curvature. For the matter component, we assume that it is an ideal gas, and of the Chaplygin gas, from the Weyl integrable gravity a scalar field is introduced by a geometric approach which provides an interaction with the matter component.We calculate the stationary points for the field equations and we study their stability properties. Furthermore, we solve the inverse problem for the case of an ideal gas and prove that the gravitational field equations can follow from the variation of a Lagrangian function. Finally, variational symmetries are applied for the construction of analytic and exact solutions.

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De Sitter Solutions in Einstein–Gauss–Bonnet Gravity

Cited by 25 publications

References 72 publications

A Refined Einstein-Gauss-Bonnet Inflationary Theoretical Framework

A Refined Einstein-Gauss-Bonnet Inflationary Theoretical Framework

Deviation from Slow-Roll Regime in the EGB Inflationary Models with r ∼ Ne−1

Dynamical Analysis and Cosmological Evolution in Weyl Integrable Gravity

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