运动弦线的自场

中文摘要 AI 辅助

我们讨论了最近提出的量 $J_{s}$ 在抑制弦线自场对其谱的贡献方面的有效性，该量在场论模拟中用于追踪衰变宇宙弦发射的轴子。我们计算了自场对该量谱的贡献，以及对无限长直弦通常计算的 $\phi\partial_{t}\alpha$ 谱的贡献。尽管我们证明了 $J_s$ 方法是一个实质性的改进，但我们也指出，这种高度对称的模型并未捕捉到自场对更复杂形状弦线（这在网络模拟中很典型）所发射谱的全部贡献。然后，我们使用正弦扰动的直弦模拟在数值上说明了这一点。对于这种简单构型，我们利用自场扣除方法，成功地将自场和辐射对 $J_{s}$ 谱的贡献分离开来。这使我们能够表明，$J_{s}$ 的谱仍然由弦振荡的 $n=1$ 模式主导，该模式可归因于自场，并且在去除自场时被大幅抑制。我们还证明，该模式主要由沿平行于弦方向的变化所激发，而这种变化在非连通段模型中缺失，arXiv:2512.13653 使用该模型声称 $J_{s}$ 在抑制自场对谱的贡献方面的有效性。

英文摘要

We discuss the effectiveness of the recently proposed quantity $J_{s}$ in suppressing the contribution of a string's self-field to its spectrum, which is used in field theory simulations to track the emission of axions by decaying cosmic strings. We compute the contribution of the self-field to the spectrum of this quantity and to the usually computed spectrum of $ϕ\partial_{t}α$ for an infinitely long straight string. Although we demonstrate that the $J_s$ approach is a substantial improvement, we also point out that this highly symmetric model doesn't capture the full contribution of the self-field to the spectrum emitted by strings of a more complex shape, which are typical in network simulations. We then illustrate this point numerically using a simulation of a sinusoidally perturbed straight string. For this simple configuration, we managed to separate the contribution from the self-field and the radiation to the spectrum of $J_{s}$, using the self-field subtraction method. This allows us to show that the spectrum of $J_{s}$ is still dominated by the $n=1$ mode of the string's oscillation, which can be attributed to the self-field and is largely suppressed when the self-field is removed. We also demonstrate that this mode is predominantly sourced by variations along the direction parallel to the string, which is missing in the unconnected segment model, used by arXiv:2512.13653 to claim the effectiveness of $J_{s}$ in suppressing the self-field's contribution to the spectrum.

补充信息

备注

8 pages, 3 figures;