Beyond the power spectrum: primordial and secondary non-Gaussianity in the microwave background

Understand

Cosmic microwave background observations are most commonly analyzed by estimating the power spectrum.

• In the limit where the CMB statistics are perfectly Gaussian, this extracts all the information, but the CMB also contains detectable non-Gaussian contributions from secondary, and possibly primordial, sources.
• We review possible sources of CMB non-Gaussianity and describe statistical techniques which are optimized for measuring them, complementing the power spectrum analysis.
• The machinery of $N$-point correlation functions provides a unifying framework for optimal estimation of primordial non-Gaussian signals or gravitational lensing.