Comparison of Spectral Index Determinations

The index n of a power law power spectrum of primordial density fluctuations, P (k) ∝ k, has been estimated using many different techniques. The most precise compare the COBE 1 DMR large angular scale ∆T to the amplitude of the large scale structure, but these are also the most model-dependent. The COBE DMR ∆T has also been compared to the degree-scale ∆T from several experiments. And finally, a relatively model-independent value of n can derived from the COBE data alone, but the small range of angular scales covered by COBE limits the precision of these methods.