Preprint typeset in JHEP style- HYPER VERSION The Strong Multifield Slowroll Condition and Spiral Inflation

Abstract

Abstract: We point out the existing confusions about the slowroll parameters and conditions for multifield inflation. If one requires the field to roll down the gradient flow, we find that only articles adopting the Hubble slowroll expansion are on the right track and a correct condition can be found in a recent book by Liddle and Lyth. We further analyze this condition and show that the gradient flow requirement is stronger than just asking for a slowly changing, quasi-de Sitter solution. Therefore it is possible to have a multifield slowroll model that does not follow the gradient flow. Consequently, it no longer requires the gradient to be small, so it even bypasses the first slowroll condition and some related no-go theorem from string theory. We provide the “spiral inflation” as a generic blueprint of such inflation model and show that it relies on a monodromy locus—a common structure in string theory effective potentials