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arXiv 0908.0425astro-ph.COgr-qc
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自序标量场的引力波

Gravitational waves from self-ordering scalar fields

Elisa Fenu, Daniel G. Figueroa, Ruth Durrer, Juan Garcia-Bellido

摘要:

在早期宇宙中,只要发生的过程足够剧烈,就会产生大量的引力波。这些引力波背景的光谱在亚视界尺度上已被广泛研究的文献。本文分析了产生时超视界尺度上的引力波谱的形状和振幅。这样的引力波是从随机取向的标量场的自排序中预期的,这些场可以在热相变期间或混合膨胀后的预热期间出现。我们发现,如果引力波源的行为只在哈勃时间的一小部分,在频率低于在生产时的膨胀率的引力波频谱表现为$Ω_{\rm GW}(f) \propto f^3$的振幅太小,无法观察到的引力波天文台,如LIGO,LISA或BBO。另一方面,如果源活动的时间长得多,直到一个给定的模式,最初是超视界($kη_* \ll 1$),进入视界,对于$kη\gtrsim 1$,我们发现,引力波能量密度是频率无关的,即标度不变。此外,它的幅度为大统一体规模的情况下,原来是在BBO的范围和灵敏度和边缘检测的LIGO和LISA。这种新的引力波背景可以与暴胀过程中产生的引力波竞争,区分两者可能需要额外的信息。

英文摘要:

Gravitational waves were copiously produced in the early Universe whenever the processes taking place were sufficiently violent. The spectra of several of these gravitational wave backgrounds on subhorizon scales have been extensively studied in the literature. In this paper we analyze the shape and amplitude of the gravitational wave spectrum on scales which are superhorizon at the time of production. Such gravitational waves are expected from the self ordering of randomly oriented scalar fields which can be present during a thermal phase transition or during preheating after hybrid inflation. We find that, if the gravitational wave source acts only during a small fraction of the Hubble time, the gravitational wave spectrum at frequencies lower than the expansion rate at the time of production behaves as $Ω_{\rm GW}(f) \propto f^3$ with an amplitude much too small to be observable by gravitational wave observatories like LIGO, LISA or BBO. On the other hand, if the source is active for a much longer time, until a given mode which is initially superhorizon ($kη_* \ll 1$), enters the horizon, for $kη\gtrsim 1$, we find that the gravitational wave energy density is frequency independent, i.e. scale invariant. Moreover, its amplitude for a GUT scale scenario turns out to be within the range and sensitivity of BBO and marginally detectable by LIGO and LISA. This new gravitational wave background can compete with the one generated during inflation, and distinguishing both may require extra information.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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