Relic Gravitational Waves and their Detection
Relic Gravitational Waves and their Detection
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DOI：
10.1103/physrevd.74.043503
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发表时间：
2006-04
影响因子：
5
通讯作者：
Wen Zhao;Yang-Hong Zhang
中科院分区：
文献类型：
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作者：
Wen Zhao;Yang-Hong Zhang
作为暴胀的有力证据，遗迹引力波（RGW）已经被广泛研究。虽然它们还没有被探测到，但通过观测已经获得了一些约束条件。未来的RGW探测实验主要有两种：微波背景实验和激光干涉仪。在本文中，我们研究了这些当前的约束和未来实验的检测能力。通过求解膨胀流方程，采用解析法和数值法两种方法计算了RGW ${\ensuremath{\Omega}}_{g}(k)$的强度。通过第一种方法，我们在$\ensuremath{\nu}=0.1\text{ }\text{ }\mathrm{Hz}$处获得了一个界${\ensuremath{\Omega}}_{g}l3.89\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}$，其中我们使用了当前对标量谱指数和张量-标量比的约束；此外，我们还考虑了红移抑制效应、加速膨胀效应和中微子对RGW的阻尼效应。但是${\ensuremath{\Omega}}_{g}(k)$的解析表达式依赖于特定的暴胀模型，并且不适用于频率非常高的波。数值方法对于高频率的波更为精确。给出了一个与暴胀参数无关的界${\ensuremath{\Omega}}_{g}l8.62\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}14}$，它适用于任何单场慢滚暴胀模型。在考虑当前对通货膨胀参数的约束后，该边界变为${\ensuremath{\Omega}}_{g}l2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}17}$。这两种方法得出了一致的结论：目前来自LIGO、大爆炸核合成和脉冲星定时的RGW约束过于宽松，无法给单场暴胀模型提供任何约束，而来自WMAP的约束相对更严格。未来的激光干涉仪对较小张量比的RGW探测效果更好，而CMB实验对较大张量比的RGW探测效果更好。这些检测方法对于RGW的检测是互补的。
As strong evidence for inflation, relic gravitational waves (RGW) have been extensively studied. Although they have not been detected yet, some constraints have been achieved by observations. Future experiments for RGW detection are mainly of two kinds: CMB experiments and laser interferometers. In this paper, we study these current constraints and the detective abilities of future experiments. We calculate the strength of RGW ${\ensuremath{\Omega}}_{g}(k)$ using two methods: the analytic method and the numerical method, by solving the inflationary flow equations. By the first method, we obtain a bound ${\ensuremath{\Omega}}_{g}l3.89\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}16}$ at $\ensuremath{\nu}=0.1\text{ }\text{ }\mathrm{Hz}$, where we have used the current constraints on the scalar spectral index and the tensor-scalar ratio; furthermore, we have taken into account the redshift-suppression effect, the accelerating expansion effect, and the neutrino damping effect on RGW. But the analytic expression of ${\ensuremath{\Omega}}_{g}(k)$ depends on specific inflationary models and does not apply well for the waves with very high frequencies. The numerical method is more precise for the waves with high frequencies. It gives a bound ${\ensuremath{\Omega}}_{g}l8.62\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}14}$, which is independent of the inflationary parameters, and applies to any single-field slow-roll inflationary model. After considering the current constraints on the inflationary parameters, this bound becomes ${\ensuremath{\Omega}}_{g}l2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}17}$. These two methods give consistent conclusions: the current constraints on RGW from LIGO, big bang nucleosynthesis, and pulsar timing are too loose to give any constraint for the single-field inflationary models, and the constraints from WMAP are relatively tighter. Future laser interferometers are more effective for detecting RGW with the smaller tensor-scalar ratio, but the CMB experiments are more effective for detecting the waves with the larger ratio. These detection methods are complementary to each other for the detection of RGW.