论文标题
GW170817之后恢复非最小Horndeski样理论：动力学耦合校正了Einstein-Gauss-Bonnet膨胀
Reviving non-Minimal Horndeski-like Theories after GW170817: Kinetic Coupling Corrected Einstein-Gauss-Bonnet Inflation
论文作者
论文摘要
在最近的两个中子恒星合并的GW170817事件之后，许多弦乐纠正了宇宙学理论，就面临着非可变性危险。这是由于以下事实：这些理论中的大多数原始产生了巨大的吸引力。其中包括在拉格朗日（Lagrangian）中包含非最小动力学耦合校正项的理论，属于Horndeski理论的子类。在这项工作中，我们演示了如何复兴这些理论，并展示了这些理论如何在天然单位中以$ C_T^2 = 1 $产生原始的引力波，从而符合GW170817事件。如我们所示，如果爱因斯坦 - 加斯 - 邦纳特理论的引力作用还包含形式的动力学耦合$ \ sim配对（ϕ）g^{μν} \partial_μx\partial_μx\ partial_v ϕ $在标量场依赖性耦合函数上，高斯 - 骨网项也是动力学耦合的非最小耦合。我们仅通过假设标量场的缓慢滚动动力学来广泛研究这种理论的现象学含义。因此，我们简要研究了标量场以恒定方式演变的案例。通过使用一些说明性示例，我们证明了手头理论框架的生存能力很容易实现。 Also, theories containing terms of the form $\sim ξ(ϕ)\Boxϕg^{μν}\partial_μϕ\partial_νϕ$ and $\sim ξ(ϕ)\left(g^{μν}\partial_μϕ\partial_νϕ\right)^2$ also lead to the same gravitational wave speed as the theory we shall study in this paper, so this covers a较大的Horndeski理论。
After the recent GW170817 event of the two neutron stars merging, many string corrected cosmological theories confronted the non-viability peril. This was due to the fact that most of these theories produce massive gravitons primordially. Among these theories were the ones containing a non-minimal kinetic coupling correction term in the Lagrangian, which belong to a subclass of Horndeski theories. In this work we demonstrate how these theories may be revived and we show how these theories can produce primordial gravitational waves with speed $c_T^2=1$ in natural units, thus complying with the GW170817 event. As we show, if the gravitational action of an Einstein-Gauss-Bonnet theory also contains a kinetic coupling of the form $\sim ξ(ϕ) G^{μν}\partial_μϕ\partial_νϕ$, the condition of having primordial massless gravitons, or equivalently primordial gravitational waves with speed $c_T^2=1$ in natural units, results to certain conditions on the scalar field dependent coupling function of the Gauss-Bonnet term, which is also the non-minimal coupling of the kinetic coupling. We extensively study the phenomenological implications of such a theory focusing on the inflationary era, by only assuming slow-roll dynamics for the scalar field. Accordingly, we briefly study the case that the scalar field evolves in a constant-roll way. By using some illustrative examples, we demonstrate that the viability of the theoretical framework at hand may easily be achieved. Also, theories containing terms of the form $\sim ξ(ϕ)\Boxϕg^{μν}\partial_μϕ\partial_νϕ$ and $\sim ξ(ϕ)\left(g^{μν}\partial_μϕ\partial_νϕ\right)^2$ also lead to the same gravitational wave speed as the theory we shall study in this paper, so this covers a larger class of Horndeski theories.
