The peak distribution in COBE maps: A non-linear test in a noisy environment

We analyse the statistical distribution of temperature maxima and minima in COBE-DMR maps. For power law spectra this distribution implies a quadrupole amplitude consistent with more conventional analyses of COBE data using fits of several harmonics, but not with the directly measured quadrupole. In our test the dependence of the quadrupole on the spectral index is relatively weak, so the discrepancy remains large even for a spectral indexn≈2. We thereby provide further support for the existence of an infrared cut-off in the cosmic spectrum.