NEW STATISTICAL TESTS APPLIED ON THE FOUR-YEAR COBE–DMR MAPS

Abstract

We apply new statistical tests on the four-year 53 GHz DMR data and show that there is excessive probability for the existence of coherent temperature discontinuities hidden in the CMB maps around the galactic poles. Such discontinuities could have been produced by long strings in our horizon. Comparing Monte–Carlo simulations with the 53 GHz DMR maps we find that the probability for the existence of a coherent discontinuity with amplitude 0.2×(δT/T) rms superposed on the Gaussian fluctuations is more than double the corresponding probability when no discontinuity is present. This result cannot be used as a detection because the DMR value of the introduced statistical variable MSD is consistent with a pure Gaussian map at a 20% level. However, when combined with the recent findings of Ferreira et al.1 it points out that the confidence by which the COBE maps are assumed to be Gaussian should probably be reduced.