2018/06/30 by Chris Pattison, Vincent Vennin, Hooshyar Assadullahi +1 · 76 citations
Physics and Astronomy · #Attractor #Black Holes and Theoretical Physics #Cosmology and Gravitation Theories #Field (mathematics) #Geometry #Inflation (cosmology) #Inflaton #Inflection point #Mathematical analysis #Mathematical physics #Physics #Quantum mechanics #Slow roll #Solar and Space Plasma Dynamics #astro-ph.CO #gr-qc #hep-th
paper · pdf · doi:10.1088/1475-7516/2018/08/048
published in Journal of Cosmology and Astroparticle Physics 2018(08), 048 (Institute of Physics) · 23 pages, 6 figures, matches version published in JCAP
openalex publication_date 2018/08/31 · arxiv created 2018/09/11 · arxiv updated 2018/09/19 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
It is often claimed that the ultra-slow-roll regime of inflation, where the dynamics of the inflaton field are friction dominated, is a non-attractor and/or transient. In this work we carry out a phase-space analysis of ultra-slow roll in an arbitrary potential, V (ϕ). We show that while standard slow roll is always a dynamical attractor whenever it is a self-consistent approximation, ultra-slow roll is stable for an inflaton field rolling down a convex potential with M Pl V ''>| V '| (or for a field rolling up a concave potential with M Pl V ''<−| V '|). In particular, when approaching a flat inflection point, ultra-slow roll is always stable and a large number of \efolds may be realised in this regime. However, in ultra-slow roll, is not a unique function of ϕ as it is in slow roll and dependence on initial conditions is retained. We confirm our analytical results with numerical examples.