QCD 交叉跃迁传递函数：PTA 频段标量诱导引力波
QCD Crossover Transfer Functions for Scalar-Induced Gravitational Waves in the PTA Band
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中文总结 AI 辅助
本文研究 QCD 交叉跃迁对 PTA 频段标量诱导引力波的影响，通过求解标准模型热历史中的运动方程并编制传递函数，发现该效应可改变谱高约 55%，且影响 NANOGrav 15 年数据推断的峰值参数。
中文摘要 AI 辅助
脉冲星计时阵列（PTA）合作组织已报告在纳赫兹频段存在随机引力波（GW）背景的证据。若由增强的原初曲率扰动在二阶上产生的标量诱导引力波对该信号有贡献，则尺度上的巧合使其直接对 QCD 交叉跃迁附近状态方程的软化敏感。我们求解了标准模型（SM）热历史中张量和标量运动方程，并编制了传递函数表，以供当前及未来的 PTA 分析直接使用。我们表明，相对于辐射主导预期，这一 SM 效应在 PTA 频段内可将诱导谱的高度改变高达约 55%，其符号取决于源模式是在交叉跃迁之前还是之后跨越视界。利用破缺幂律曲率功率谱拟合 NANOGrav 15 年数据，我们发现纳入交叉跃迁会使推断的峰值振幅和尺度发生偏移，其幅度可能已对与原初黑洞过产生约束的比较具有相关性。随着未来更灵敏的 PTA 数据集使振幅和尺度的统计不确定性减小，这一 SM 效应的重要性将日益增加，届时忽略它可能显著偏差推断结果。
英文摘要
Pulsar timing array (PTA) collaborations have reported evidence for a stochastic gravitational wave (GW) background in the nHz band. Should scalar-induced GWs, sourced at second order by enhanced primordial curvature perturbations, contribute to this signal, a coincidence of scales makes them directly sensitive to the softening of the equation of state around the QCD crossover. We solve the tensor and scalar equations of motion across the Standard Model (SM) thermal history and tabulate the transfer functions for direct use in present and future PTA analyses. We show that this SM effect modifies the height of the induced spectrum by up to $\approx55\%$ across the PTA band relative to the radiation-domination expectation, with either sign depending on whether the source modes cross the horizon before or after the crossover. Fitting the NANOGrav 15-year data with a broken-power-law curvature power spectrum, we find that including the crossover shifts the inferred peak amplitude and scale by an amount that could already be relevant for the comparison with primordial black hole overproduction bounds. The importance of this SM effect will grow as the statistical uncertainty on the amplitude and scale shrinks with future, more sensitive PTA datasets, at which point neglecting it could significantly bias the inference.
发表机构
- Università degli Studi di Padova（帕多瓦大学）
- INFN, Sezione di Padova（意大利国家核物理研究所帕多瓦分部）
- University of Sussex（萨塞克斯大学）
- University of Fukui（福井大学）
机构由 AI 辅助整理，请以论文原文为准。
