What can WMAP tell us about the very early Universe? New physics as an explanation of the suppressed large scale power and running spectral index

The Wilkinson Microwave Anisotropy Probe microwave background data may be giving us clues about new physics at the transition from a 'stringy' epoch of the Universe to the standard Friedmann-Robertson-Walker description. Deviations on large angular scales of the data, as compared to theoretical expectations, as well as running of the spectral index of density perturbations, can be explained by new physics whose scale is set by the height of an inflationary potential. As examples of possible signatures for this new physics, we study the cosmic microwave background spectrum for two string inspired models: (1) modifications to the Friedmann equations and (2) velocity dependent potentials. The suppression of low 'l' modes in the microwave background data arises due to the new physics. In addition, the spectral index is red (n<1) on small scales and blue (n>1) on large scales, in agreement with data