Kavli Affiliate: Toshiya Namikawa
| First 5 Authors: Toshiya Namikawa, Toshiya Namikawa, , ,
| Summary:
The recent measurement of baryonic acoustic oscillations (BAO) by the Dark
Energy Spectroscopic Instrument (DESI) reveals a mild tension with observations
of the cosmic microwave background (CMB) within the standard $Lambda$CDM
cosmological model. This discrepancy leads to a preference for a total neutrino
mass that is lower than the minimum value inferred from neutrino oscillation
experiments. Alternatively, this tension can be eased within $Lambda$CDM by
assuming a higher optical depth ($tau simeq 0.09$), but such a value
conflicts with large-scale CMB polarization data. We point out that cosmic
birefringence, as suggested by recent Planck reanalyses, resolves this
discrepancy if the birefringence angle varies significantly during
reionization. Specifically, we consider the fact that the measured cosmic
birefringence angle $beta_0=0.34pm0.09,(1,sigma),$deg has the phase
ambiguity, i.e., the measured rotation angle is described by
$beta=beta_0+180n,$deg ($nin mathbbZ$). We show that cosmic
birefringence induced by axion-like particles with nonzero $n$ suppresses the
reionization bump, allowing a higher $tau$ consistent with data. We provide a
viable parameter space where the birefringence effect simultaneously accounts
for the low-$ell$ polarization spectra, the Planck $EB$ correlations, and the
elevated value of $tau$, suggesting a key role for cosmic birefringence in
current cosmological tensions.
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