Significance of the largest scale CMB fluctuations in WMAP
Abstract
We investigate anomalies reported in the cosmic microwave background maps from the Wilkinson Microwave Anisotropy Probe (WMAP) satellite on very large angular scales and discuss possible interpretations. Three independent anomalies involve the quadrupole and octopole: (1) The cosmic quadrupole on its own is anomalous at the 1in20 level by being low (the cutsky quadrupole measured by the WMAP team is more strikingly low, apparently due to a coincidence in the orientation of our Galaxy of no cosmological significance); (2) the cosmic octopole on its own is anomalous at the 1in20 level by being very planar; (3) the alignment between the quadrupole and octopole is anomalous at the 1in66 level. Although the a priori chance of all three occurring is 1 in 24000, the multitude of alternative anomalies one could have looked for dilutes the significance of such a posteriori statistics. The simplest small universe model where the universe has toroidal topology with one small dimension of order onehalf the horizon scale, in the direction toward Virgo, could explain the three items above. However, we rule this model out using two topological tests: the S statistic and the matched circle test.
 Publication:

Physical Review D
 Pub Date:
 March 2004
 DOI:
 10.1103/PhysRevD.69.063516
 arXiv:
 arXiv:astroph/0307282
 Bibcode:
 2004PhRvD..69f3516D
 Keywords:

 98.80.Es;
 Observational cosmology;
 Astrophysics;
 General Relativity and Quantum Cosmology;
 High Energy Physics  Theory
 EPrint:
 N.B. that our results do not rule out the recently proposed dodecahedron model of Luminet, Weeks, Riazuelo, Lehoucq &