  The angular power spectrum C_l is extracted from the 4 year COBE DMR data
with a 20 degree galactic cut, using the narrowest window functions possible.
The average power in eight multipole bands is also computed, and plotted
together with a compilation of power spectrum measurements from other
experiments. The COBE results are found to be consistent with an n=1 power
spectrum with the normalization Qrmsps=18 microkelvin reported by the COBE DMR
team. Certain non-standard cosmologies, such as "small universe" models with
nontrivial spatial topology, predict power spectra which are not smooth
functions. Rather, they contain bumps and wiggles that may not have been
detected by other data analysis techniques such as the Hauser-Peebles method
(Wright etal 1996), the band-power method (Hinshaw etal 1996) and
orthogonalized spherical harmonics (Gorski etal 1996), since these methods all
give broader window functions that can smear such features out beyond
recognition. On the large angular scales probed by COBE, the Universe thus
appears to be kind to us, presenting a power spectrum that is a simple smooth
function.
