TY - JOUR
T1 - Cosmological perturbations of axion with a dynamical decay constant
AU - Kobayashi, Takeshi
AU - Takahashi, Fuminobu
N1 - Funding Information:
This work is supported by MEXT KAKENHI Grant Numbers 15H05889 and 15K21733 (F.T.), JSPS KAKENHI Grant Numbers 26247042(F.T.), and 26287039 (F.T.), World Premier International Research Center Initiative (WPI Initiative), MEXT, Japan (F.T.).
PY - 2016/8/25
Y1 - 2016/8/25
N2 - A QCD axion with a time-dependent decay constant has been known to be able to accommodate high-scale inflation without producing topological defects or too large isocurvature perturbations on CMB scales. We point out that a dynamical decay constant also has the effect of enhancing the small-scale axion isocurvature perturbations. The enhanced axion perturbations can even exceed the periodicity of the axion potential, and thus lead to the formation of axionic domain walls. Unlike the well-studied axionic walls, the walls produced from the enhanced perturbations are not bounded by cosmic strings, and thus would overclose the universe independently of the number of degenerate vacua along the axion potential.
AB - A QCD axion with a time-dependent decay constant has been known to be able to accommodate high-scale inflation without producing topological defects or too large isocurvature perturbations on CMB scales. We point out that a dynamical decay constant also has the effect of enhancing the small-scale axion isocurvature perturbations. The enhanced axion perturbations can even exceed the periodicity of the axion potential, and thus lead to the formation of axionic domain walls. Unlike the well-studied axionic walls, the walls produced from the enhanced perturbations are not bounded by cosmic strings, and thus would overclose the universe independently of the number of degenerate vacua along the axion potential.
KW - axions, Cosmic strings
KW - cosmological perturbation theory
KW - domain walls
KW - monopoles
KW - physics of the early universe
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U2 - 10.1088/1475-7516/2016/08/056
DO - 10.1088/1475-7516/2016/08/056
M3 - Article
AN - SCOPUS:84985955343
VL - 2016
JO - Journal of Cosmology and Astroparticle Physics
JF - Journal of Cosmology and Astroparticle Physics
SN - 1475-7516
IS - 8
M1 - 056
ER -