Can axion clumps be formed in a pre-inflationary scenario?
Can axion clumps be formed in a pre-inflationary scenario?
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DOI：
10.1088/1475-7516/2021/02/015
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发表时间：
2020-04
影响因子：
6.4
通讯作者：
Hayato Fukunaga;N. Kitajima;Y. Urakawa
中科院分区：
文献类型：
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作者：
Hayato Fukunaga;N. Kitajima;Y. Urakawa
QCD轴子和类轴子粒子（ALP）是暗物质令人信服的候选者。对于QCD轴子，当Peccei-Quinn（PQ）对称性在暴胀后自发破缺时，大的初始涨落会导致轴子团簇的形成。另一方面，当对称性在暴胀过程中已经被破坏时，人们认为，由于初始轴子波动的振幅很小，轴子团的形成不会发生。我们重新审视这种普遍的理解，考虑QCD轴子和ALP。在我们的分析中，即使我们考虑一个非常微调的初始条件，也没有观察到QCD轴子的团块形成。同时，对于一个ALP，它允许一个更一般的潜在形式，我们表明，通过快子不稳定性或/和共振不稳定性，考虑多个余弦势的块的形成可以发生。
The QCD axion and an axion-like particle (ALP) are compelling candidates of dark matter. For the QCD axion, it is known that when the Peccei-Quinn (PQ) symmetry is spontaneously broken after inflation, the large initial fluctuation can lead to axion clump formation. On the other hand, when the symmetry is already broken during inflation, it has been believed that the axion clump formation does not occur due to the small amplitude of the initial axion fluctuation. We revisit this prevailing understanding, considering both the QCD axion and an ALP. In our analysis, the clump formation was not observed for the QCD axion even if we consider an extremely fine-tuned initial condition. Meanwhile, for an ALP which allows a more general potential form, we show that the clump formation can take place through the tachyonic instability or/and the resonance instability, considering a multiple cosine potential.