修正来自畴壁的引力波红外尾部
Fixing IR tail of gravitational waves from domain walls
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中文总结 AI 辅助
研究早期宇宙物质不均匀性产生引力波时红外光谱摆动问题，借助CosmoLattice代码模拟畴壁网络，提出消除寄生摆动的数值程序，可恢复真实光谱，该程序通用且能应用于其他假设源模拟。
中文摘要 AI 辅助
早期宇宙中物质不均匀性剧烈演化期间引力波（GW）产生的数值模拟产生了光谱中高度摆动的红外部分。这些摆动直接从两点相关函数获得，是非物理的，对应于GW平均平方振荡幅度中的寄生双频项，因此必须消除。深红外行为可基于一般原理预测，例如由因果关系考虑确定。然而，对于实际观测（如NANOGrav的观测）重要的以及只能从数值模拟推断的是光谱最大值附近的红外斜率。它反映了GW产生全盛期的动力学，因此必须准确预测。我们借助CosmoLattice代码对畴壁网络进行数值模拟来说明这个问题。我们提出了一种数值程序来消除这些寄生摆动，从而恢复真实光谱。该程序相当通用，可应用于早期宇宙中其他可能的GW假设源的数值模拟。该程序需要在GW产生终止后将模拟扩展几个哈勃时间。我们通过数值模拟检查发现，通过PRS处方对标量场方程中不同部分进行人工缩放可获得的技术上自然的长时间模拟扩展，即使源项适当重新缩放，也会给出错误的GW光谱。
英文摘要
Numerical simulations of gravitational waves (GW) production during violent evolution of matter inhomogeneities in the early Universe yield highly wiggle infrared parts of the spectra. Obtained directly from the two-point correlation function, these wiggles are nonphysical, corresponding to the parasitic, double frequency terms in naively averaged squared oscillation amplitudes of GW, and hence must be washed out. The deep infrared behavior can be predicted on general grounds, e.g. fixed by causality considerations. However, what matters for real observations, e.g. like that of NANOGrav, and what can be only inferred from numerical simulations, is the infrared slope near the maximum of the spectrum. It reflects the dynamics responsible for the GW production in its heyday, and hence must be accurately predicted. We illustrate the problem with numerical simulations of the Domain Wall network performed with the help of code CosmoLattice. We suggest a numerical procedure to smooth out these parasitic wiggles, which allows us to recover the true spectrum. Being quite generic, it may be applied to numerical simulations of other hypothetical sources of GW possibly operating in the early Universe. The procedure requires to extend the simulation by a few Hubble times after termination of the GW production. We checked with numerical simulations, that the technically natural long-time extension of simulations, which becomes available via artificial scaling of different parts in the scalar sector equations provided by PRS prescription, gives wrong GW spectra even if the source terms are properly rescaled.
