arXiv 2007.042562020-07astro-ph.COgr-qc

原初引力波的传播速度

Propagating Speed of Primordial Gravitational Waves

William Giarè, Fabrizio Renzi

备注：: 25 pages, 8 figures. Edited to match Phys. Rev. D published version
发表信息：: Phys. Rev. D 102, 083530 (2020)
DOI：: 10.1103/PhysRevD.102.083530

摘要：

原初引力波，即由量子暴胀涨落引起的度规扰动的背景，如果被测量，既可以为原初暴胀提供实质性证据，也可以揭示极高能量尺度下的物理学。在这项工作中，我们专注于他们的传播速度。使用有效场论的方法，我们介绍了一个随时间变化的传播速度$c_{\rm T}(t)$表明，也从广义相对论（GR）预测$c_{\rm T}(t) = c$小偏差可以导致可测试的后果。我们推导出一组方程的传播速度和它的时间依赖性的暴胀参数和推广通常的慢卷一致性关系。通过引入新的广义相容关系，结合小尺度和大尺度数据，我们得到了具有非平凡原始张量速度的暴胀的模型无关约束。特别地，我们将其尺度依赖性限制为在68% C. L.时为$d\log c_{\rm T} / d\log k=0.082^{+0.047}_{-0.11}$。而我们只得到了95% C. L.时的下限$c_{\rm T}>0.22\,c$。.我们还将主尺度$k_*=0.05\rm{Mpc}^{-1}$处的张量标量比约束为95%C. L时的$r<0.0599$。这与普朗克合作提供的结果一致。由于张量谱的适当的小尺度参数化，我们得到严格的限制张量倾斜$n_{\rm T}=-0.084^{+0.10}_{-0.047}$在68% C. L。$α_{\rm T}=d\,n_{\rm T}/d\log k=0.0141^{+0.0035}_{-0.021}$和$β_{\rm T}=d\,α_{\rm T}/d\log k= -0.0061^{+0.010}_{-0.0014}$在其运行中均为68% C. L.。我们的研究结果表明，一个显着的协议与标准的慢滚的预测，并证明目前的数据可以显着约束偏离GR的暴胀能量尺度。

英文摘要：

Primordial Gravitational Waves, i.e. a background of metric perturbations sourced by the quantum inflationary fluctuations, if measured, could both provide a substantial evidence for primordial inflation and shed light on physics at extremely high energy scales. In this work we focus on their propagating speed. Using an effective field theory approach we introduce a time-dependent propagating speed $c_{\rm T}(t)$ showing that also small deviations from the General Relativity (GR) prediction $c_{\rm T}(t) = c$ can lead to testable consequences. We derive a set of equations that relate the propagating speed and its time dependence to the inflationary parameters and that generalize the usual slow roll consistency relations. Imposing the new generalized consistency relations and combining small and large scales data, we derive model independent constraints on inflation with non-trivial primordial tensor speed. In particular we constrain its scale dependence to be $d\log c_{\rm T} / d\log k=0.082^{+0.047}_{-0.11}$ at 68% C.L. while we only derive the lower bound $c_{\rm T}>0.22\,c$ at 95% C.L. . We also constrain the tensor-to-scalar ratio at the pivot scale $k_*=0.05\rm{Mpc}^{-1}$ to be $r<0.0599$ at 95% C.L. in agreement with the result provided by the Planck collaboration. Thanks to a proper small scale parameterization of the tensor spectrum we derive stringent constraints on the tensor tilt $n_{\rm T}=-0.084^{+0.10}_{-0.047}$ at 68% C.L. and on its runnings $α_{\rm T}=d\,n_{\rm T}/d\log k=0.0141^{+0.0035}_{-0.021}$ and $β_{\rm T}=d\,α_{\rm T}/d\log k= -0.0061^{+0.010}_{-0.0014}$ both at 68% C.L. Our results show a remarkable agreement with the standard slow roll predictions and prove that current data can significantly constrain deviations from GR on the inflationary energy scales.

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英文摘要：

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