This paper forecasts how well the Ali CMB Polarization Telescope (AliCPT) can test a set of puzzling, large‑scale features seen in the cosmic microwave background (CMB) temperature maps, but now using E‑mode polarization. E‑mode polarization is an independent signal from the same early universe fluctuations that produced the temperature pattern. Because it is independent, a confirmed anomaly in E‑modes would be harder to dismiss as a random fluke in the temperature data.

The authors built 1,000 simulated sky maps and added models of Galactic foregrounds, instrument noise, and realistic observing footprints. They cleaned those maps with a component‑separation pipeline called NILC (a cleaning method) and ran four statistical tests that have been used to describe the temperature anomalies: dipole modulation (a hemispheric power asymmetry), lack of large‑angle correlations, alignment of the quadrupole and octopole modes, and a point‑parity asymmetry between odd and even spherical harmonics. They considered two noise cases for AliCPT — a “baseline” first‑year sensitivity and a deeper “goal” four‑year sensitivity — and also studied the effect of combining AliCPT with measurements from the Simons Observatory Large Aperture Telescope (SO LAT).

A concrete result concerns dipole modulation. The team injected a modulation of amplitude Ad = 0.07 into simulated E‑modes and tested a local‑variance estimator. They find that the combined AliCPT+SO dataset would very likely detect that injected modulation at about the 99% confidence level. In other words, if an E‑mode hemispheric asymmetry at that level exists, the joint observations should be able to reject the “fluke” hypothesis with high confidence.

The authors also highlight important limitations. AliCPT’s planned wide‑scan footprint is large (the paper treats a wide‑scan region and a smaller deep‑scan region) but not full sky. Limited sky coverage can bias some statistics or increase their uncertainty. In the simulations, AliCPT alone showed possible biases or enlarged errors for tests of the quadrupole‑octopole alignment and the point‑parity asymmetry. Adding SO’s northern or southern coverage largely restored the statistical distributions to those expected for an ideal full‑sky measurement, approaching the so‑called cosmic‑variance limit — the fundamental uncertainty from observing only one sky.