More varieties of hybrid inflation

Abstract

It is pointed out that hybrid inflation can be implemented with the inflaton field rolling away from the origin instead of towards it. This `inverted&#39; hybrid inflation has a spectral index $ n < 1 $, in contrast with ordinary hybrid inflation which has $ n \gtrsim 1 $, so a measured value of $n$ substantially different from 1 would distinguish the two. Other generalisations of hybrid inflation are also considered.