Elliptic inflation: generating the curvature perturbation without slow-roll

Abstract

There are many inflationary models in which inflaton field does not satisfy the slow-roll condition. However, in such models, it is always difficult to generate the curvature perturbation during inflation. Thus, to generate the curvature perturbation, one must introduce another component to the theory. To cite a case, curvatons may generate dominant part of the curvature perturbation after inflation.However, we have a question whether it is unrealistic to consider the generation of the curvature perturbation during inflation without slow-roll. Assuming multi-field inflation, we encounter the generation of the curvature perturbation during inflation

Generating the curvature perturbation with instant preheating

“…Comparing Eq. (3.11) and (3.6), we find that the condition ζ DBI /ζ P R−DBI ≫ 1 that is needed for the "standard" fluctuation ζ DBI to dominate over ζ P R is written as 13) where δφ 2 ≃ H/2π is considered. Following Ref.…”

“…Inflation ends with waterfall Inflation ends with preheating Lyth[11] This paper m 1 ∼ m 2 T. Matsuda [13] W. Kolb,A. Riotto and A. Vallinotto[22] We consider the instant preheating model [18] as the process through which the inflaton decays into lighter particles.…”

Running spectral index from shooting-star moduli

“…See ref. [7] for more details of the fluctuation related to the target brane. In fact, the multi-inflaton model has been applied to brane inflation to solve the serious η-problem in string theory [7].…”

Brane inflation without slow-roll

“…9 In a common case, there is no exact symmetry that protects all the masses of the position moduli, and thus the equipotential surface of the potential becomes an ellipsoid [12]. On the other hand, if…”

“…The condition considered in ref. [12] is very common in brane inflationary models when extra dimensions are added. 5 The benefit of the model is that concern over symmetry is not warranted, as the potential along the equipotential surface is flat by definition.…”