We study the contribution to the QCD axion dark matter abundance that is produced by string defects during the so-called scaling regime. Clear evidence of scaling violations is found, the most conservative extrapolation of which strongly suggests a large number of axions from strings. In this regime, nonlinearities at around the QCD scale are shown to play an important role in determining the final abundance. The overall result is a lower bound on the QCD axion mass in the post-inflationary scenario that is substantially stronger than the naive one from misalignment.

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来自琴弦的更多斧头

我们研究了所谓的结垢过程中弦缺陷产生的对QCD轴突暗物质丰度的贡献。发现了明显的违反音阶的证据，最保守的推断强烈表明弦上有大量的轴。在这种情况下，QCD尺度附近的非线性在确定最终丰度中起着重要作用。总体结果是，在通货膨胀后的情况下，QCD轴突质量的下限比未对准的天真的质量强得多。