A search for cosmic topology in the final WMAP data

Abstract: A search for matched circle pairs of similar temperature fluctuations in the final WMAP 9yr data is carried out. Such a signature is expected if the space of the Universe is multiply connected. We investigate the relation between the pixel resolution of cosmic microwave background (CMB) maps and a Gaussian smoothing in order to lower the probability for missing matched circle pairs. CMB maps having the 3-torus topology are generated with the characteristics of the WMAP satellite in order to determine how large the smoothing should be chosen in CMB maps disturbed by detector noise. The V- and W-band data are analysed with respect to matched circle pairs and a tentatively signal is found for a circle pair, which lies, however, close to the plane of the Galaxy. It is, however, inconclusive whether this signal is generated by chance, is due to residual foregrounds contained in the V- and W-band maps, or is due to a genuine topology.