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arXiv · 1804.09116

Inflation with Gauss-Bonnet coupling

Zhu Yi·Yungui Gong·Mudassar Sabir
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Abstract

We consider inflationary models with the inflaton coupled to the Gauss-Bonnet term assuming a special relation $δ_1=2λε_1$ between the two slow-roll parameters $δ_1$ and $ε_1$. For the slow-roll inflation, the assumed relation leads to the reciprocal relation between the Gauss-Bonnet coupling function $ξ(ϕ)$ and the potential $V(ϕ)$, and it leads to the relation $r=16(1-λ)ε_1$ that reduces the tensor-to-scalar ratio $r$ by a factor of $1-λ$. For the constant-roll inflation, we derive the analytical expressions for the scalar and tensor power spectra, the scalar and tensor spectral tilts, and the tensor-to-scalar ratio to the first order of $ε_1$ by using the method of Bessel function approximation. The tensor-to-scalar ratio is reduced by a factor of $1-λ+λ\tilde η$. Comparing the derived $n_s$-$r$ with the observations, we obtain the constraints on the model parameters $\tildeη$ and $λ$.

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Zhu Yi, Yungui Gong, Mudassar Sabir. 2018-10-05. Inflation with Gauss-Bonnet coupling. https://doi.org/10.1103/physrevd.98.083521

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