Is cosmic birefringence due to dark energy or dark matter? A tomographic approach

A pseudoscalar "axionlike" field, $ϕ$, may explain the $3σ$ hint of cosmic birefringence observed in the $EB$ power spectrum of the cosmic microwave background (CMB) polarization data. Is $ϕ$ dark energy or dark matter? A tomographic approach can answer this question. The effective mass of dark energy field responsible for the accelerated expansion of the Universe today must be smaller than $m_ϕ\simeq 10^{-33}$ eV. If $m_ϕ\gtrsim 10^{-32}$ eV, $ϕ$ starts evolving before the epoch of reionization and we should observe different amounts of birefringence from the $EB$ power spectrum at low ($l\lesssim 10$) and high multipoles. Such an observation, which requires a full-sky satellite mission, would rule out $ϕ$ being dark energy. If $m_ϕ\gtrsim 10^{-28}$ eV, $ϕ$ starts oscillating during the epoch of recombination, leaving a distinct signature in the $EB$ power spectrum at high multipoles, which can be measured precisely by ground-based CMB observations. Our tomographic approach relies on the shape of the $EB$ power spectrum and is less sensitive to miscalibration of polarization angles.

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