This paper asks whether the Ali CMB Polarization Telescope (AliCPT), a ground-based experiment in the Northern Hemisphere, can detect unusual large-scale patterns in the CMB E-mode polarization. These patterns, or “anomalies,” were first seen in temperature maps from WMAP and Planck and include a hemispherical power asymmetry (dipole modulation), a lack of correlations on very large angles, an alignment between the largest multipoles (quadrupole and octopole), and an odd–even parity imbalance. E-mode polarization provides an independent check because it comes from the same early conditions as the temperature signal but is measured in a different way, so it can help decide whether the temperature anomalies are flukes or signs of new physics.

The authors made forecasts by building 1,000 simulated skies that include a Gaussian CMB signal based on the Planck best-fit cosmology, realistic Galactic foregrounds (using the PySM3 sky model), and instrument noise. They processed the maps with a component-separation method called NILC (Needlet Internal Linear Combination), which aims to remove foregrounds and leave the E-mode signal. The simulations included two AliCPT noise cases—“baseline” (first-year sensitivity) and “goal” (four-year sensitivity, with a higher cumulative detector exposure of 48 mod·yr)—and a separate deep-scan region of about 13% of the sky. The main wide-scan footprint used in the forecasts covers roughly half the sky in the northern hemisphere.

To test anomaly detection, the team applied four statistical estimators to the cleaned E-mode maps. For dipole modulation they validated a local-variance estimator using a set of deliberately modulated simulations with an input modulation amplitude Ad = 0.07. They found that when AliCPT is combined with the Simons Observatory (SO) Large Aperture Telescope (LAT), the injected E‑mode modulation would likely be detected at about the 99% confidence level. More generally, combining AliCPT with SO brings the joint survey close to the statistics expected in an ideal full‑sky experiment, reducing the chance that limited sky coverage alone produces misleading results.