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Rectifying Einstein-Gauss-Bonnet inflation in view of GW170817
Nuclear Physics B ( IF 2.8 ) Pub Date : 2020-08-07 , DOI: 10.1016/j.nuclphysb.2020.115135
S.D. Odintsov , V.K. Oikonomou , F.P. Fronimos

In this work we introduce a new theoretical framework for Einstein-Gauss-Bonnet theories of gravity, which results to particularly elegant, functionally simple and transparent gravitational equations of motion, slow-roll indices and the corresponding observational indices. The main requirement is that the Einstein-Gauss-Bonnet theory has to be compatible with the GW170817 event, so the gravitational wave speed cT2 is required to be cT21 in natural units. This assumption was also made in a previous work of ours, but in this work we express all the related quantities as functions of the scalar field. The constraint cT21 restricts the functional form of the scalar Gauss-Bonnet coupling function ξ(ϕ) and of the scalar potential V(ϕ), which must satisfy a differential equation. However, by also assuming that the slow-roll conditions hold true, the resulting equations of motion and the slow-roll indices acquire particularly simple forms, and also the relation that yields the e-foldings number is N=ϕiϕfξ/ξdϕ, a fact that enables us to perform particularly simple calculations in order to study the inflationary phenomenological implications of several models. As it proves, the models we presented are compatible with the observational data, and also satisfy all the assumptions made during the process of extracting the gravitational equations of motion. More interestingly, we also investigated the phenomenological implications of an additional condition ξ/ξ1, which is motivated by the slow-roll conditions that are imposed on the scalar field evolution and on the Hubble rate. As we shall show, the resulting constraint differential equation that constrains the functional form of the scalar Gauss-Bonnet coupling function ξ(ϕ) and of the scalar potential V(ϕ), is simpler in this case, and in effect the whole study becomes somewhat easier. As we also show, compatibility with the observational data can also be achieved in this case too, in a much simpler and less constrained way. Our approach opens a new window in viable Einstein-Gauss-Bonnet theories of gravity.



中文翻译:

鉴于GW170817修正了爱因斯坦-高斯-邦尼特的通货膨胀

在这项工作中,我们为爱因斯坦-高斯-邦纳特引力理论引入了一个新的理论框架,从而产生了特别优雅,功能简单且透明的运动引力方程,慢速滚动指数和相应的观测指数。主要要求是爱因斯坦-高斯-邦涅特理论必须与GW170817事件兼容,因此引力波速度CŤ2 必须是 CŤ21个以自然单位。这个假设也是在我们以前的工作中做出的,但是在这项工作中,我们将所有相关量表示为标量字段的函数。约束CŤ21个 限制标量Gauss-Bonnet耦合函数的函数形式 ξϕ 和标量势 Vϕ,它必须满足一个微分方程。然而,通过还假设慢摇条件成立,得到的运动方程和慢摇指数获得特别简单的形式,并且产生电子折叠数的关系为ñ=ϕ一世ϕFξ''/ξdϕ,这一事实使我们能够执行特别简单的计算,以便研究几种模型的通胀现象学含义。事实证明,我们提出的模型与观测数据兼容,并且还满足在提取运动引力方程的过程中所做的所有假设。更有趣的是,我们还研究了附加条件的现象学含义ξ/ξ''1个,这是由标量场演化和哈勃速率所施加的慢速滚动条件引起的。正如我们将要展示的那样,由此产生的约束微分方程约束了标量高斯-邦尼耦合函数的函数形式ξϕ 和标量势 Vϕ在这种情况下,更加简单,实际上整个研究变得更加容易。正如我们还显示的,在这种情况下,也可以以更简单和受约束更少的方式实现与观测数据的兼容性。我们的方法为可行的爱因斯坦-高斯-邦尼特引力理论打开了一个新窗口。

更新日期:2020-08-14
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