Inflation with a constant rate of roll

By H. Motohashi, A. Starobinsky, J. Yokoyama. 2014

262 citations recorded by the source corpus.

We consider an inflationary scenario where the rate of inflaton roll defined by ̈ϕ/H ϕ̇ remains constant. The rate of roll is small for slow-roll inflation, while a generic rate of roll leads to the interesting case of ‘constant-roll’ inflation. We find a general exact solution for the inflaton potential required for such inflaton behaviour. In this model, due to non-slow evolution of background, the would-be decaying mode of linear scalar (curvature) perturbations may not be neglected. It can even grow for some values of the model parameter, while the other mode always remains constant. However, this always occurs for unstable solutions which are not attractors for the given potential. The most interesting particular cases of constant-roll inflation remaining viable with the most recent observational data are quadratic hilltop inflation (with cutoff) and natural inflation (with an additional negative cosmological constant). In these cases even-order slow-roll parameters approach non-negligible constants while the odd ones are asymptotically vanishing in the quasi-de Sitter regime.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/3ddddc49a785939611da9f8d12fed8c122f9a1a2

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Citations in the corpus

Primordial black holes from string inflation (2018, unknown): “These backgrounds are characterised by the parameter α defined as [72, 73]: φ̈ ≡ −(3 + α)Hφ̇ .”
Primordial black holes from a tiny bump/dip in the inflaton potential (2019, background): “where the potential term is given by the following exact expression [67] z′′ z = a(2)H(2) ( 2− 1 + 3 2 2 + 1 4 (2)2 − 1 2 1 2 + 1 2 2 3 ) , (A.”
Primordial black holes from α-attractors (2018, background): “[59], after examining particular solutions of the equation of motion for the inflaton field with constant-roll, i.”