Kavli Affiliate: Toshiya Namikawa
| First 5 Authors: Dongdong Zhang, Elisa G. M. Ferreira, Ippei Obata, Toshiya Namikawa,
| Summary:
Cosmic birefringence, the observed rotation of the polarization plane of the
cosmic microwave background (CMB), serves as a compelling probe for
parity-violating physics beyond the Standard Model. This study explores the
potential of ultralight axion-like particle (ALP) dark matter to explain the
observed cosmic birefringence in the CMB. We focus on the previously
understudied mass range of $10^{-25}$ eV to $10^{-23}$ eV, where ALPs start to
undergo nonlinear clustering in the late universe. Our analysis incorporates
recent cosmological constraints and considers the washout effect on CMB
polarization. We find that for models with ALP masses $10^{-25}$ eV $lesssim
m_phi lesssim 10^{-23}$ eV and birefringence arising from late ALP
clustering, the upper limit on the ALP-photon coupling constant, imposed by the
washout effect, is stringently lower than the coupling required to account for
the observed static cosmic birefringence signal. This discrepancy persists
regardless of the ALP fraction in dark matter. Furthermore, considering ALPs
with masses $m_phigtrsim$ $10^{-23}$ eV cannot explain static birefringence
due to their rapid field oscillations, our results indicate that, all ALP dark
matter candidates capable of nonlinear clustering in the late universe and thus
contributing mainly to the rotation angle of polarized photons, are
incompatible with explaining the static cosmic birefringence signal observed in
Planck and WMAP data.
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