Tachyonic Preheating in Plateau Inflation

TL;DR

This paper develops an analytic theory of tachyonic preheating in plateau inflation models, showing inflaton fragmentation occurs rapidly and the scalar-to-tensor ratio remains extremely small, with numerical validation.

Contribution

It introduces a comprehensive analytic framework for tachyonic preheating in plateau inflation, including backreaction effects, and confirms rapid inflaton fragmentation across models.

Findings

Inflaton fragments within an e-fold in all studied models.

Scalar-to-tensor ratio is extremely small, below 10^{-7}.

Analytic predictions match numerical estimates.

Abstract

Plateau inflation is an experimentally consistent framework in which the scale of inflation can be kept relatively low. Close to the edge of the plateau, scalar perturbations are subject to a strong tachyonic instability. Tachyonic preheating is realized when, after inflation, the oscillating inflaton repeatedly re-enters the plateau. We develop the analytic theory of this process and expand the linear approach by including backreaction between the coherent background and growing perturbations. For a family of plateau models, the analytic predictions are confronted with numerical estimates. Our analysis shows that the inflaton fragments in a fraction of an $e$-fold in all examples supporting tachyonic preheating, generalizing the results of previous similar studies. In these scenarios, the scalar-to-tensor ratio is tiny, $r<10^{-7}$.