Conversations in the dark: cross-correlating birefringence and LSS to constrain axions
S. Arcari, N. Bartolo, A. Greco, A. Gruppuso, M. Lattanzi, P. Natoli
arXiv:2407.02144v1 Announce Type: new
Abstract: Unveiling the dark sector of the Universe is one of the leading efforts in theoretical physics. Among the many models proposed, axions and axion-like particles stand out due to their solid theoretical foundation, capacity to contribute significantly to both dark matter and dark energy, and potential to address the small-scale crisis of $Lambda$CDM. Moreover, these pseudo-scalar fields couple to the electromagnetic sector through a Chern-Simons parity-violating term, leading to a rotation of the plane of linearly polarized waves, namely cosmic birefringence. We explore the impact of the axion-parameters on anisotropic birefringence and study, for the first time, its cross-correlation with the spatial distribution of galaxies, focusing on ultralight axions with masses $10^{-33},{rm eV}le m_phile10^{-28},{rm eV}$. Through this novel approach, we investigate the axion-parameter space in the mass $m_phi$ and initial misalignment angle $theta_i$, within the framework of early dark energy models, and constrain the axion-photon coupling $g_{phigamma}$ required to achieve unity in the signal-to-noise ratio of the underlying cross-correlation, computed with the instrument specifications of Euclid and forthcoming CMB-polarization data. Our findings reveal that for masses below $10^{-32},{rm eV}$ and initial misalignment angles greater in absolute value than $pi/4$, the signal-to-noise ratio not only exceeds unity but also surpasses that achievable from the auto-correlation of birefringence alone (up to a factor 7), highlighting the informative potential of this new probe. Additionally, given the late-time evolution of these low-mass axions, the signal stems from the epoch of reionization, providing an excellent tool to single out the birefringence generated during this period.arXiv:2407.02144v1 Announce Type: new
Abstract: Unveiling the dark sector of the Universe is one of the leading efforts in theoretical physics. Among the many models proposed, axions and axion-like particles stand out due to their solid theoretical foundation, capacity to contribute significantly to both dark matter and dark energy, and potential to address the small-scale crisis of $Lambda$CDM. Moreover, these pseudo-scalar fields couple to the electromagnetic sector through a Chern-Simons parity-violating term, leading to a rotation of the plane of linearly polarized waves, namely cosmic birefringence. We explore the impact of the axion-parameters on anisotropic birefringence and study, for the first time, its cross-correlation with the spatial distribution of galaxies, focusing on ultralight axions with masses $10^{-33},{rm eV}le m_phile10^{-28},{rm eV}$. Through this novel approach, we investigate the axion-parameter space in the mass $m_phi$ and initial misalignment angle $theta_i$, within the framework of early dark energy models, and constrain the axion-photon coupling $g_{phigamma}$ required to achieve unity in the signal-to-noise ratio of the underlying cross-correlation, computed with the instrument specifications of Euclid and forthcoming CMB-polarization data. Our findings reveal that for masses below $10^{-32},{rm eV}$ and initial misalignment angles greater in absolute value than $pi/4$, the signal-to-noise ratio not only exceeds unity but also surpasses that achievable from the auto-correlation of birefringence alone (up to a factor 7), highlighting the informative potential of this new probe. Additionally, given the late-time evolution of these low-mass axions, the signal stems from the epoch of reionization, providing an excellent tool to single out the birefringence generated during this period.