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 ΛCDM. 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 eV ≤ m_ϕ ≤ 10^-28 eV. Through this novel approach, we investigate the axion-parameter space in the mass m_ϕ and initial misalignment angle θ_i , within the framework of early dark energy models, and constrain the axion-photon coupling g_ϕγ 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 eV and initial misalignment angles greater in absolute value than π/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.

中文翻译：

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黑暗中的对话：交叉相关双折射和 LSS 约束轴子


揭开宇宙的暗区是理论物理学的领先努力之一。在提出的众多模型中，轴子和轴子类粒子因其坚实的理论基础、对暗物质和暗能量做出重大贡献的能力以及解决 ΛCDM 小规模危机的潜力而脱颖而出。此外，这些伪标量场通过违反 Chern-Simons 奇偶校验的项耦合到电磁扇区，导致线性极化波平面的旋转，即宇宙双折射。我们探讨了轴子参数对各向异性双折射的影响，并首次研究了它与星系空间分布的互相关，重点关注质量为 ^10-33 eV ≤ m_φ≤ ^10-28 eV 的超轻轴子 m。通过这种新颖的方法，我们在早期暗能量模型的框架内研究了质量 m_φ 和初始错位角 θ_i 中的轴子参数空间，并约束了实现基础互相关的信噪比统一的轴子-光子耦合 g_φγ，使用 Euclid 的仪器规格和即将到来的 CMB 极化数据计算。我们的研究结果表明，对于低于 ^10-32 eV 的质量和绝对值大于 π/4 的初始错位角，信噪比不仅超过了统一，而且超过了单独双折射自相关所能实现的（高达因子 7），突出了这种新探针的信息潜力。 此外，鉴于这些低质量轴子的后期演化，该信号源于再电离时代，为挑出在此期间产生的双折射提供了极好的工具。