Large scale anomalies in the microwave background: causation and correlation

Area of Science:

• Cosmology
• Astrophysics
• Cosmic Microwave Background (CMB) analysis

Background:

• Existing analyses of large-scale anomalies in the microwave sky are often post-hoc, lacking quantified look-elsewhere effects.
• Apparent anomalies may arise from specific inhomogeneities in the early Universe rather than statistical fluctuations.

Purpose of the Study:

• To contrast a priori physical models of early Universe inhomogeneities with a posteriori anomaly detection methods.
• To demonstrate that physical models can predict correlations with polarization and large-scale structure, mitigating cosmic variance.
• To quantitatively assess potential large-scale anomalies in the Universe through a generalized physical modeling approach.

Main Methods:

• Development and application of physical models for early Universe inhomogeneities.
• Computation of apparent spatial curvature induced by large-scale inhomogeneities.
• Illustrative example using a single plane wave inhomogeneity to model low-l mode alignment and power spectrum odd-even asymmetry.

Main Results:

• Physical models offer a framework for understanding and quantifying microwave sky anomalies.
• Apparent spatial curvature from inhomogeneities is typically small, enabling self-consistent analysis.
• A single plane wave inhomogeneity model successfully explains a significant portion of the claimed odd-even asymmetry in power spectra.

Conclusions:

• Physical models provide a more robust and quantitative approach to assessing large-scale cosmic anomalies.
• This methodology reduces reliance on statistical methods and addresses limitations like cosmic variance.
• The proposed approach can be generalized for a comprehensive analysis of cosmic anomalies.