A new parameter in attractor single-field inflation

Jinn Ouk Gong, Misao Sasaki

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


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, cs2 and s. Two illustrative examples are presented to discuss the non-slow-roll dynamics of the inflaton field consistent with observations.

Original languageEnglish
Pages (from-to)390-394
Number of pages5
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
StatePublished - 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.


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