## Abstract

We revisit the notion of slow-roll in the context of general single-field inflation. As a generalization of slow-roll dynamics, we consider an inflaton ϕ in an attractor phase where the time derivative of ϕ is determined by a function of ϕ, ϕ˙=ϕ˙(ϕ). In other words, we consider the case when the number of e-folds N counted backward in time from the end of inflation is solely a function of ϕ, N=. N(ϕ). In this case, it is found that we need a new independent parameter to properly describe the dynamics of the inflaton field in general, in addition to the standard parameters conventionally denoted by ε, η, c_{s}^{2} and s. Two illustrative examples are presented to discuss the non-slow-roll dynamics of the inflaton field consistent with observations.

Original language | English |
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Pages (from-to) | 390-394 |

Number of pages | 5 |

Journal | Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics |

Volume | 747 |

DOIs | |

State | Published - 1 Jul 2015 |

### Bibliographical note

Funding Information:JG is grateful to the Yukawa Institute for Theoretical Physics for hospitality while this work was under progress. JG acknowledges the Max-Planck-Gesellschaft, the Korea Ministry of Education, Science and Technology, Gyeongsangbuk-Do and Pohang City for the support of the Independent Junior Research Group at the Asia Pacific Center for Theoretical Physics. This work is also supported in part by a Starting Grant through the Basic Science Research Program of the National Research Foundation of Korea ( 2013R1A1A1006701 ) and the JSPS Grant-in-Aid for Scientific Research (A) No. 21244033 .

Publisher Copyright:

© 2015 The Authors.