Are the CMB large-angle anomalies statistical flukes or physics?
In plain words
Several odd patterns appear on the largest scales of the microwave sky, each with odds of roughly one in a hundred to one in a thousand. With a single sky to look at, it is hard to know if they mean anything.
Precise statement
The anomalies are: low quadrupole power, lack of temperature correlation above 60 degrees (S_1/2), quadrupole-octopole alignment, hemispherical power asymmetry, the cold spot and an odd-even parity asymmetry, each at $p \sim 0.1 \text{ to } 1\,\text{percent}$ in LCDM, with a posteriori choice of statistics. Decide whether they are flukes or physical by testing predictions fixed in advance on independent data (large-angle E-mode polarization, CMB lensing, galaxy surveys).
What would settle it
Pre-registered tests on large-angle polarization and lensing maps whose outcome under LCDM is predicted conditional on the temperature map.
Status in the literature
Unverified note
2025 re-analyses of foreground-cleaned low-multipole maps still find the temperature anomalies at similar significance.
Related problems
- More general than Is the hemispherical power asymmetry a real dipolar modulation?
- More general than Does the large-angle correlation deficit appear in E-mode polarization?