CBR anisotropy and the running of the scalar spectral index.

Accurate (∼ 1%) predictions for the anisotropy of the Cosmic Background Radiation (CBR) are essential for using future high-resolution (∼ 1) CBR maps to test cosmological models. In many inflationary models the variation (“running”) of the spectral index of the spectrum of density perturbations is a significant effect and leads to changes of around 1% to 10% in the CBR power spectrum. We propose a general method for taking running into account which uses the derivative of the spectral index (dn/d ln k). Conversely, highresolution CBR maps may be able to determine dn/d ln k, giving important information about the inflationary potential. 98.70.V, 98.80.C Typeset using REVTEX