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 constraintthat the gravitational wave speed is in natural units, results to a constraintdifferential 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 , 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.

我们提供了一个改进的、更简化的爱因斯坦-高斯-博内暴胀理论框架，它与 GW170817 对引力波速度的观测约束兼容。与以前的工作一样，引力波速度是自然单位的约束导致了一个约束微分方程，该方程将标量场的耦合函数与高斯-博内不变量ξ ( ϕ ) 和标量势V ( ϕ ) 联系起来。对标量场和哈勃速率采用慢滚条件，与以前的工作相比，通过进一步假设，这是由慢滚参数激发的，我们成功地为慢滚指数、张量和标量光谱指数以及张量与标量比提供了更简单的表达式。我们通过使用一个简单的幂律标量耦合函数ξ ( ϕ ) ∼ ϕ ^ν的说明性示例来举例说明我们改进的理论框架，并且我们证明了由此产生的暴胀现象学与最新的普朗克数据兼容。此外，这个特定的模型产生了一个蓝色倾斜的张量光谱指数，所以我们简要讨论了用这个模型描述 NANOGrav 结果的观点，正如最近的文献中所指出的那样。