The 4 year COBE normalization and large-scale structure

We present an analysis of the 4 year data from the COBE DMR experiment. We use a Karhunen-Loeve expansion of the pixel data to calculate the normalization and goodness of fit of a range of models of structure formation. This technique produces unbiased normalization estimates and is capable of determining the normalization of any particular model with a statistical uncertainty of 7%. We present a parameterization of the normalization and likelihood function which summarizes our results for a wide range of models. We use the COBE normalization to compute small-scale fluctuation amplitudes for a variety of models and discuss the implications of these results for theories of large-scale structure.