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arXiv · 2511.04459

Study the nature of dynamical dark energy by measuring the CMB polarization rotation angle

Hua Zhai·Si-Yu Li·Yang Liu·Yiwei Zhong·Hong Li·Yaqiong Li·Congzhan Liu·Mingzhe Li·Xinmin Zhang
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Abstract

Recent results from the Dark Energy Spectroscopic Instrument (DESI) support the dynamical dark energy. Intriguingly, the data favor a transition of the dark energy equation of state across $w=-1$, a hallmark of the Quintom scenario. In this paper, we consider a different approach to the dynamical nature of dark energy by investigating its interaction with ordinary matters, specifically the Chern-Simons (CS) interaction with photons. In cosmology, this interaction rotates the polarized plane of the cosmic microwave background (CMB) photons, which induces non-zero polarized TB and EB power spectra. We forecast this measurement with the Ali CMB Polarization Telescope (AliCPT) experiment. We take the best-fit value of the isotropic rotation angle from Planck data as our fiducial input. We project that 11 module-year (modyr) of observations will yield an improved detection sensitivity with a significance $\sim 5σ$, given a calibration precision of $0.1^\circ$ in the polarization angle. We also forecast AliCPT's sensitivity to the amplitude of a scale invariant spectrum of the anisotropic polarization rotation field. With $50$~modyr of observations, the large-aperture configuration is expected to reach $σ_{A_{\mathrm{CB}}}\sim10^{-2}$, offering a sixfold improvement over the small-aperture design and enabling competitive tests of spatial fluctuations in the dark energy field.

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Hua Zhai, Si-Yu Li, Yang Liu, Yiwei Zhong, Hong Li, Yaqiong Li, Congzhan Liu, Mingzhe Li, Xinmin Zhang. 2026-08-20. Study the nature of dynamical dark energy by measuring the CMB polarization rotation angle. https://doi.org/10.1088/1475-7516%2F2026%2F08%2F008

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