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

TL;DR

This paper explores how the Chern-Simons interaction affects CMB polarization to probe dynamical dark energy, forecasting detection capabilities of the AliCPT experiment with improved sensitivity over existing data.

Contribution

It introduces a novel approach to studying dynamical dark energy through CMB polarization rotation measurements with AliCPT, including forecasts for detection significance and sensitivity to anisotropic effects.

Findings

AliCPT can detect polarization rotation angle with ~5σ significance after 11 module-years.

Large-aperture configuration improves sensitivity to anisotropic rotation spectrum by a factor of six.

Forecasts suggest competitive constraints on spatial fluctuations of dark energy.

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 $\sim 5\sigma$, 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 $\sigma_{A_{\mathrm{CB}}}\sim10^{-2}$, offering a sixfold improvement over the small-aperture design and enabling competitive tests of spatial fluctuations in the dark energy field.