The striking GW170817 event indicated that the graviton is nearly massless, since the gamma rays emitted from the two neutron stars merging arrived almost simultaneously with the gravitational waves. Thus, the graviton must also be massless during the inflationary and post-inflationary era, since there is no obvious reason to believe otherwise. In this letter we shall investigate the theoretical implications of the constraint that the graviton is massless to an Einstein-Gauss-Bonnet theory with linear coupling of the scalar field to the four-dimensional Gauss-Bonnet invariant. As we show, the constraint of having gravitational wave speed of the primordial gravitational waves equal to one severely restricts the dynamics of the scalar field, imposing a direct constant-roll evolution on it. Also, as we show, the spectral index of the primordial scalar perturbations for the GW170817-compatible Einstein-Gauss-Bonnet theory with linear coupling is different in comparison to the same t...

中文翻译：

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具有线性耦合的爱因斯坦-高斯-贝内通量的近乎无质量的引力意味着标量场的恒定侧倾

引人注目的GW170817事件表明引力子几乎是无质量的，因为两个中子星合流产生的伽马射线几乎与引力波同时到达。因此，在通货膨胀时代和通货膨胀后时代，引力子也必须是无质量的，因为没有明显的理由相信它。在这封信中，我们将研究标量场与四维高斯-贝内不变式线性耦合的引力子对爱因斯坦-高斯-邦内理论的无质量约束的理论含义。如我们所示，使原始引力波的引力波速度等于1的约束严重限制了标量场的动力学，并对其施加了直接的恒定侧倾演化。而且，正如我们所展示的，