TY - JOUR
T1 - Can axion clumps be formed in a pre-inflationary scenario?
AU - Fukunaga, Hayato
AU - Kitajima, Naoya
AU - Urakawa, Yuko
N1 - Publisher Copyright:
© 2021 IOP Publishing Ltd and Sissa Medialab.
PY - 2021/2
Y1 - 2021/2
N2 - 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.
AB - 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.
KW - axions
KW - particle physics - cosmology connection
KW - physics of the early universe
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U2 - 10.1088/1475-7516/2021/02/015
DO - 10.1088/1475-7516/2021/02/015
M3 - Article
AN - SCOPUS:85101524157
VL - 2021
JO - Journal of Cosmology and Astroparticle Physics
JF - Journal of Cosmology and Astroparticle Physics
SN - 1475-7516
IS - 2
M1 - 015
ER -