Precision calculations of the gravitational wave background spectrum from inflation
Precision calculations of the gravitational wave background spectrum from inflation
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DOI：
10.1103/physrevd.79.103501
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发表时间：
2008-04
影响因子：
5
通讯作者：
S. Kuroyanagi;T. Chiba;N. Sugiyama
中科院分区：
文献类型：
--
作者：
S. Kuroyanagi;T. Chiba;N. Sugiyama
本文对各种暴胀模型在宽频率范围内的暴胀过程中量子涨落引起的引力波背景谱进行了数值计算。我们考虑到四个成分：在通货膨胀期间的标量场动力学不使用慢滚近似，在再加热过程中的一个小的耦合常数的标量场的费米衰变，在辐射主导的时代，和自由流中微子的各向异性应力的有效自由度g{sub *}的变化。通过数值求解暴胀期间和暴胀之后到目前为止引力波的演化，所有这些效应都可以在广泛的频谱上得到全面而准确的研究，即使是在非常高的频率下。我们发现，频谱显示（i）一个很大的偏差，从频谱不太准确的泰勒展开周围的CMB规模使用慢滚近似，（ii）一个特征频率依赖性由于再加热效应，和（iii）阻尼由于g{sub *}的变化和中微子各向异性应力。我们建议，未来的引力波背景的分析应该考虑到这样一个事实，即使用泰勒展开的分析估计高估了频谱的振幅。
The spectrum of the gravitational wave background originating from quantum fluctuations during inflation is calculated numerically for various inflation models over a wide range of frequencies. We take into account four ingredients: the scalar field dynamics during inflation making no use of the slow-roll approximation, the fermionic decay of the scalar field with a small coupling constant during the reheating process, the change of the effective number of degrees of freedom g{sub *} in the radiation-dominated era, and the anisotropic stress of free-streaming neutrinos. By numerically solving the evolution of gravitational waves during and after inflation up to the present, all of these effects can be examined comprehensively and accurately over a broad spectrum, even at very high frequencies. We find that the spectrum shows (i) a large deviation from the spectrum less accurate obtained by Taylor expanding around the CMB scale using the slow-roll approximation, (ii) a characteristic frequency dependence due to the reheating effect, and (iii) damping due to the g{sub *} changes and the neutrino anisotropic stress. We suggest that future analysis of the gravitational wave background should take into consideration the fact that analytical estimates using the Taylor expansion overestimate the amplitude of the spectrum.