Inflation with a constant rate of roll
Abstract
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 slowroll inflation, while a generic rate of roll leads to the interesting case of 'constantroll' inflation. We find a general exact solution for the inflaton potential required for such inflaton behaviour. In this model, due to nonslow evolution of background, the wouldbe 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 constantroll 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 evenorder slowroll parameters approach nonnegligible constants while the odd ones are asymptotically vanishing in the quaside Sitter regime.
 Publication:

Journal of Cosmology and Astroparticle Physics
 Pub Date:
 September 2015
 DOI:
 10.1088/14757516/2015/09/018
 arXiv:
 arXiv:1411.5021
 Bibcode:
 2015JCAP...09..018M
 Keywords:

 Astrophysics  Cosmology and Nongalactic Astrophysics;
 General Relativity and Quantum Cosmology;
 High Energy Physics  Theory
 EPrint:
 12 pages, 11 figures