TY - JOUR
T1 - Relaxing the cosmological moduli problem by low-scale inflation
AU - Ho, Shu Yu
AU - Takahashi, Fuminobu
AU - Yin, Wen
N1 - Funding Information:
This work is supported by GP-PU Program, Tohoku University (S.Y.H), by JSPS KAK-ENHI Grant Numbers JP15H05889 (F.T.), JP15K21733 (F.T.), JP17H02875 (F.T.), JP17H02878(F.T.), by NRF Strategic Research Program NRF-2017R1E1A1A01072736 (W.Y.), and by World Premier International Research Center Initiative (WPI Initiative), MEXT, Japan.
Publisher Copyright:
© 2019, The Author(s).
PY - 2019/4/1
Y1 - 2019/4/1
N2 - We show that the cosmological abundance of string axions is much smaller than naive estimates if the Hubble scale of inflation, H inf , is sufficiently low (but can still be much higher than the axion masses) and if the inflation lasts sufficiently long. The reason is that the initial misalignment angles of the string axions follow the Bunch-Davies distribution peaked at the potential minima. As a result, the cosmological moduli problem induced by the string axions can be significantly relaxed by low-scale inflation, and astrophysical and cosmological bounds are satisfied over a wide range of the mass without any fine-tuning of the initial misalignment angles. Specifically, the axion with its decay constant f ϕ = 10 16 GeV satisfies the bounds over 10 −18 eV ≲ m ϕ ≲ 10 TeV for H inf ≲ 10 keV-10 6 GeV. We also discuss cases with multiple axions and the QCD axion.
AB - We show that the cosmological abundance of string axions is much smaller than naive estimates if the Hubble scale of inflation, H inf , is sufficiently low (but can still be much higher than the axion masses) and if the inflation lasts sufficiently long. The reason is that the initial misalignment angles of the string axions follow the Bunch-Davies distribution peaked at the potential minima. As a result, the cosmological moduli problem induced by the string axions can be significantly relaxed by low-scale inflation, and astrophysical and cosmological bounds are satisfied over a wide range of the mass without any fine-tuning of the initial misalignment angles. Specifically, the axion with its decay constant f ϕ = 10 16 GeV satisfies the bounds over 10 −18 eV ≲ m ϕ ≲ 10 TeV for H inf ≲ 10 keV-10 6 GeV. We also discuss cases with multiple axions and the QCD axion.
KW - Beyond Standard Model
KW - Compactification and String Models
KW - Cosmology of Theories beyond the SM
KW - Supersymmetric Standard Model
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U2 - 10.1007/JHEP04(2019)149
DO - 10.1007/JHEP04(2019)149
M3 - Article
AN - SCOPUS:85064939326
SN - 1126-6708
VL - 2019
JO - Journal of High Energy Physics
JF - Journal of High Energy Physics
IS - 4
M1 - 149
ER -