Blue-tilted inflationary tensor spectrum and reheating in the light of NANOGrav results
Blue-tilted inflationary tensor spectrum and reheating in the light of NANOGrav results
复制标题
DOI：
10.1088/1475-7516/2021/01/071
复制
发表时间：
2020-11
影响因子：
6.4
通讯作者：
S. Kuroyanagi;Tomo Takahashi;Shuichiro Yokoyama
中科院分区：
文献类型：
--
作者：
S. Kuroyanagi;Tomo Takahashi;Shuichiro Yokoyama
我们讨论了用具有蓝倾斜原始谱的膨胀引力波(IGW)解释最近的NANOGrav结果的可能性。虽然这种IGW可以解释NANOGrav信号而不与宇宙微波背景尺度下张量标量比的上限相矛盾，但预测的光谱与大爆炸核合成(BBN)和第二次LIGO-Virgo观测运行的随机引力波背景的幅度上限之间存在很大的张力。然而，宇宙的热历史，如重新加热和后期的熵产生，影响了IGW在高频下的光谱形状，并允许避开上限。我们证明，对于标准的重加热情形，当重加热温度相对较低时，蓝色张量谱可以解释最近的NANOGrav信号，而不会与BBN和LIGO-Virgo约束相矛盾。我们进一步发现，当人们考虑后期的熵产生时，NANOGrav信号即使在瞬间重新加热的情况下也可以解释。
We discuss the possibility of explaining the recent NANOGrav results by inflationary gravitational waves (IGWs) with a blue-tilted primordial spectrum. Although such IGWs can account for the NANOGrav signal without contradicting the upper bound on the tensor-to-scalar ratio at the cosmic microwave background scale, the predicted spectrum is in strong tension with the upper bound on the amplitude of the stochastic gravitational wave background by big-bang nucleosynthesis (BBN) and the second LIGO-Virgo observation run. However, the thermal history of the Universe, such as reheating and late-time entropy production, affects the spectral shape of IGWs at high frequencies and permits evading the upper bounds. We show that, for the standard reheating scenario, when the reheating temperature is relatively low, a blue tensor spectrum can explain the recent NANOGrav signal without contradicting the BBN and the LIGO-Virgo constraints. We further find that, when one considers a late-time entropy production, the NANOGrav signal can be explained even for an instant reheating scenario.