Odd Parity Preference

Analyses of the CMB temperature field reveal a preference for odd-parity multipoles over even-parity multipoles at low ℓ, with the ratio of odd to even multipole power exceeding ΛCDM predictions at roughly the 2–3 sigma level. In a statistically isotropic Gaussian universe, there is no physical reason for parity to be preferred at any scale, and ΛCDM assigns the observed asymmetry to statistical chance. In SCT, parity asymmetry at cosmological scales is physically meaningful: it reflects the angular momentum vector of the collision, which is a pseudovector and therefore inherently parity-odd. The angular momentum-weighted collision geometry preferentially excites perturbations of odd parity in the CMB multipole expansion, because the two infalling pockets approached each other asymmetrically about the collision plane.

Specifically, the collision impact parameter defines a plane of symmetry, and the angular momentum vector is perpendicular to this plane. Perturbations in the plane of collision have even parity with respect to reflection through the plane, while perturbations perpendicular to the collision axis have odd parity. The net angular momentum deposited preferentially excites the odd-parity modes, producing the observed excess. This same mechanism that generates the odd-parity preference also generates the TB and EB correlations and the hemispherical power asymmetry; all four parity-related anomalies in the CMB are facets of the single pseudovector imprinted by the collision angular momentum, and SCT predicts that they will be correlated both in direction and in amplitude.