论文标题
诱导引力波作为宇宙热史的探测
Induced gravitational waves as a probe of thermal history of the universe
论文作者
论文摘要
标量扰动引起的重力波是小尺度上原始密度扰动光谱的探针。在本文中，我们表明他们还可以探测宇宙的热历史。我们假设宇宙经历了一个具有恒定状态参数$ w $的阶段，然后是传统的大爆炸宇宙的辐射阶段。我们发现，减速宇宙学的诱导随机引力波背景的功率谱的红外斜率与宇宙状态的方程式有关。此外，诱导的引力波谱通常在重新加热的尺度周围具有破碎的幂律形状。有趣的是，在状态参数方程的阈值$ w = 0 $以下，损坏的幂律为标量频谱中的Dirac Delta峰提供了峰值。对于有限的宽度峰，阈值根据宽度的值而变为$ W = -1/15 $。在某些情况下，这种损坏的幂律重力波谱可能会从其他来源（例如相变或全球宇宙字符串）退化为频谱。
The scalar perturbation induced gravitational waves are a probe of the primordial density perturbation spectrum on small scales. In this paper, we show that they can also probe the thermal history of the universe. We assume the universe underwent a stage with a constant equation of state parameter $w$, followed by the radiation-dominated stage of the conventional big bang universe. We find that the infrared slope of the power spectrum of the induced stochastic gravitational wave background for decelerating cosmologies is related to the equation of state of the universe. Furthermore, the induced gravitational wave spectrum has in general a broken power-law shape around the scale of reheating. Interestingly, below the threshold $w=0$ of the equation of state parameter, the broken power-law presents a peak for a Dirac delta peak in the scalar spectrum. For a finite width peak, the threshold changes to $w=-1/15$ depending on the value of the width. In some cases, such a broken power-law gravitational wave spectrum may degenerate to the spectrum from other sources like phase transitions or global cosmic strings.
