Parity in the cosmic microwave background: Space oddity

Assaf Ben-David, Ely D. Kovetz, Nissan Itzhaki

Research output: Contribution to journalArticlepeer-review

22 Scopus citations


We search for a direction in the sky that exhibits parity symmetry under reflections through a plane. We use the natural estimator, which compares the power in even and odd ℓ + m multipoles, and apply minimal blind masking of outliers to the Internal Linear Combination map in order to avoid large errors in the reconstruction of multipoles. The multipoles of the cut sky are calculated both naively and by using the covariance inversion method, and we estimate the significance of our results using ΛCDM simulations. Focusing on low multipoles, 2 ≤ ℓ ≤ ℓmax with ℓmax = 5, 6, or even 7, we find two perpendicular directions of even and odd parity in the map. While the even parity direction does not appear significant, the odd direction is quite significant - at least a 3.6σ effect.

Original languageEnglish
Article number39
JournalAstrophysical Journal
Issue number1
StatePublished - 20 Mar 2012
Externally publishedYes


  • cosmic background radiation
  • cosmology: observations

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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