Gauss–Bonnet Inflation after Planck2018

Inflationary models with a scalar field nonminimally coupled both with the Ricci scalar and with the Gauss–Bonnet term are studied. We propose the way of generalization of inflationary scenarios with the Gauss–Bonnet term and a scalar field minimally coupled with the Ricci scalar to the corresponding scenarios with a scalar field nonminimally coupled with the Ricci scalar. Using the effective potential, we construct a set of models with the same values of the scalar spectral index $$n_s$$ n s and the amplitude of the scalar perturbations $$A_s$$ A s and different values of the tensor-to-scalar ratio r.

Section: Introductionmentioning

confidence: 99%

Construction of inflationary scenarios with the Gauss–Bonnet term and nonminimal coupling

Pozdeeva

Vernov

2021

“…At present, the interest in inflationary scenarios in the cosmological models with Gauss-Bonnet term is growing [25][26][27][28][29][30][31][32][33][34][35]. In the present paper, we construct a gravity model with the Gauss-Bonnet term multiplied by a function of a scalar field which allows one to reconstruct expressions for the spectral index and the tensor-to-scalar ratio from cosmological attractor models in the slow-roll regime.…”

Section: Introductionmentioning

confidence: 99%

Generalization of cosmological attractor approach to Einstein–Gauss–Bonnet gravity

Pozdeeva

2020

We construct models with the Gauss–Bonnet term multiplied by a function of the scalar field leading to an inflationary scenario. The consideration is related to the slow-roll approximation. The cosmological attractor approach gives the spectral index of scalar perturbations which is in a good agreement with modern observation and allows for variability of the tensor-to-scalar ratio. We reconstruct models with variability of parameters, which allows one to reproduce cosmological attractor predictions for inflationary parameters in an approximation of the leading order of 1/N in Einstein–Gauss–Bonnet gravity.

“…In this simple model, the dominant modes of the primordial perturbations are predicted to be scale-invariant, adiabatic and Gaussian [31][32][33][34][35][36][37][38][39][40][41][42][43][44][45][46]. However, there is a lot of attention to the extended inflation models predicting the non-Gaussian distributed perturbations [46][47][48][49][50][51][52][53][54][55].…”

Section: Introductionmentioning

confidence: 99%

Viable intermediate inflation in the mimetic DBI model

Rashidi

Nozari

2021

Self Cite

We study the intermediate inflation in the mimetic Dirac–Born–Infeld model. By considering the scale factor as $$a=a_{0}\exp (bt^{\beta })$$ a = a 0 exp ( b t β ) , we show that in some ranges of the intermediate parameters b and $$\beta $$ β , the model is free of the ghost and gradient instabilities. We study the scalar spectral index, tensor spectral index, and the tensor-to-scalar ratio in this model and compare the results with Planck2018 TT, TE, EE + lowE + lensing + BAO + BK14 data at 68% and 95% CL. In this regard, we find some constraints on the intermediate parameters that lead to the observationally viable values of the perturbation parameters. We also seek the non-Gaussian features of the primordial perturbations in the equilateral configuration. By performing the numerical analysis on the nonlinearity parameter in this configuration, we show that the amplitude of the non-Gaussianity in the intermediate mimetic DBI model is predicted to be in the range $$-16.7<f^{equil}<-12.5$$ - 16.7 < f equil < - 12.5 . We show that, with $$0<b\le 10$$ 0 < b ≤ 10 and $$0.345<\beta <0.387$$ 0.345 < β < 0.387 , we have an instabilities-free intermediate mimetic DBI model that gives the observationally viable perturbation and non-Gaussianity parameters.