Speaker
Description
In this talk, I present implications for the cosmic birefringence from recent cosmological observables. We begin by showing constraints on cosmic birefringence induced by ALPs using the Planck $EB$ power spectrum. We find that cosmic birefringence signal is consistent with a constant rotation model and some specific ALP masses are excluded. Next, we show that cosmic birefringence can explain a higher optical depth $\tau\simeq0.09$ as a result of the DESI BAO measurements and CMB observations within the standard cosmological model. Specifically, we use the fact that the recent cosmic birefringence measurement, $\beta_0=0.34\,$deg, has the phase ambiguity, $\beta=\beta_0+180n\,$deg with $n\in\mathbb{Z}$). An ALP-induced birefringence model with a nonzero $n$ can suppress the reionization bump in the $EE$ spectrum while allowing for a large optical depth. We show a viable parameter region that simultaneously explain the large-scale CMB polarization, Planck $EB$ power spectrum, and an eleveted value of $\tau$.
| References | https://arxiv.org/abs/2506.20824, https://arxiv.org/abs/2506.22999 |
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