High energy physics and the very early universe with LISA
High energy physics and the very early universe with LISA
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高能物理和 LISA 的早期宇宙
DOI：
10.1103/physrevd.63.064030
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发表时间：
2000
影响因子：
5
通讯作者：
A. Vecchio
中科院分区：
文献类型：
--
作者：
C. Ungarelli;C. Ungarelli;A. Vecchio
引力波实验将通过对早期宇宙产生的原始引力波背景设置严格的上限或检测引力波背景，在宇宙学前沿和高能基本场结构的研究中发挥关键作用。在这里，我们讨论了在低频窗口$\ensuremath{\sim}{10}^{\ensuremath{-}6}\char21{}1$ Hz工作的星载激光干涉探测器的影响；我们分析的目的是调查一个以分数能量密度${h}_{100}^{2}\ensuremath{\Omega}\ensuremath{\sim}{10}^{\ensuremath{-}16}\ensuremath{-}{10}^{\ensuremath{-}15},$为特征的原始背景，这与“慢滚”暴胀模型的预测相一致，是否可以被激光干涉仪空间天线（LISA）或后续任务探测到。在寻找随机背景时，目前计划的LISA任务缺少两个具有不相关噪声的探测器。我们分析了通过交叉相关来自一对LISA类检测器的数据流可以实现的灵敏度改进；我们表明，这种配置是非常引人注目的，导致检测随机背景弱如${h}_{100}^{2}\ensuremath{\Omega}\ensuremath{\simeq}5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}14}.$。然而，这种仪器灵敏度不能被充分利用来测量背景的原始成分，由于大量短周期太阳质量双星系统产生的信号具有压倒性的力量。我们估计原始背景只有在分数能量密度${h}_{100}^{2}\ensuremath{\Omega}$大于$\ensuremath{\approx}5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}.$时才能被观测到。我们分析的关键结论是，无论仪器噪声水平和积分时间如何，来自未解析双星系统的随机辐射对在$\ensuremath{\sim}{10}^{\ensuremath{-}6}$ Hz和0.1 Hz之间的频率范围内搜索原始背景的灵敏度设置了基本限制。事实上，LISA达到最佳灵敏度的mHz频段并不适合探测慢滚膨胀模型。我们简要讨论了针对$\ensuremath{\sim}0.1\char21{}1$ Hz频率区域的可能的后续任务，该频率区域可能不受天体物理起源的随机背景的影响：尽管技术挑战相当大，值得仔细研究，但似乎没有基本限制阻止我们到达${h}_{100}^{2}\ensuremath{\Omega}\ensuremath{\sim}{10}^{\ensuremath{-}16},$。
Gravitational wave experiments will play a key role in the investigation of the frontiers of cosmology and the structure of fundamental fields at high energies by either setting stringent upper limits on or by detecting the primordial gravitational wave background produced in the early Universe. Here we discuss the impact of space-borne laser interferometric detectors operating in the low-frequency window $\ensuremath{\sim}{10}^{\ensuremath{-}6}\char21{}1$ Hz; the aim of our analysis is to investigate whether a primordial background characterized by a fractional energy density ${h}_{100}^{2}\ensuremath{\Omega}\ensuremath{\sim}{10}^{\ensuremath{-}16}\ensuremath{-}{10}^{\ensuremath{-}15},$ which is consistent with the prediction of ``slow-roll'' inflationary models, might be detectable by the Laser Interferometer Space Antenna (LISA) or follow-up missions. In searching for stochastic backgrounds, the presently planned LISA mission suffers from the lack of two detectors with uncorrelated noise. We analyze the sensitivity improvements that could be achieved by cross-correlating the data streams from a pair of detectors of the LISA class; we show that this configuration is extremely compelling, leading to the detection of a stochastic background as weak as ${h}_{100}^{2}\ensuremath{\Omega}\ensuremath{\simeq}5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}14}.$ However, such instrumental sensitivity cannot be fully exploited to measure the primordial component of the background, due to the overwhelming power of the signal produced by large populations of short-period solar-mass binary systems of compact objects. We estimate that the primordial background can be observed only if its fractional energy density ${h}_{100}^{2}\ensuremath{\Omega}$ is greater than $\ensuremath{\approx}5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}13}.$ The key conclusion of our analysis is that the stochastic radiation from unresolved binary systems sets a fundamental limit on the sensitivity that can be achieved in searching for the primordial background in frequencies between $\ensuremath{\sim}{10}^{\ensuremath{-}6}$ Hz and 0.1 Hz, regardless of the instrumental noise level and the integration time. Indeed, the mHz frequency band, where LISA achieves optimal sensitivity, is not suitable to probe slow-roll inflationary models. We briefly discuss possible follow-up missions aimed at the frequency region $\ensuremath{\sim}0.1\char21{}1$ Hz, which is likely to be free from stochastic backgrounds of astrophysical origin: no fundamental limits seem to prevent us from reaching ${h}_{100}^{2}\ensuremath{\Omega}\ensuremath{\sim}{10}^{\ensuremath{-}16},$ although the technological challenges are considerable and deserve careful study.