We revisit the hybrid inflation model focusing on the dynamics of the
waterfall field in an analytical way. It is shown that inflation may last long
enough during the waterfall regime for some parameter regions, confirming the
claim of Clesse. In this case the scalar spectral index becomes red, and can
fall into the best fit range of the WMAP observation.
Progress of Theoretical Physics 02/2011; 126. DOI:10.1143/PTP.126.331 · 2.06 Impact Factor