Evading Lyth bound in models of quintessential inflation

TL;DR

This paper explores models of quintessential inflation that unify early universe inflation with late-time acceleration, demonstrating how the Lyth bound can be evaded even with large tensor-to-scalar ratios, while remaining consistent with nucleosynthesis constraints.

Contribution

It introduces two classes of quintessential inflation models—one with a non-canonical kinetic term and another based on brane world inflation—that evade the Lyth bound.

Findings

Lyth bound can be evaded in both models.

Post-inflationary dynamics satisfy nucleosynthesis constraints.

Models accommodate large tensor-to-scalar ratios.

Abstract

Quintessential inflation refers to an attempt to unify inflation and late-time cosmic acceleration using a single scalar field. In this letter we consider two different classes of quintessential inflation, one of which is based upon a Lagrangian with non-canonical kinetic term $k^2(\phi)\partial^\mu \phi \partial_\mu \phi$ and a steep exponential potential while the second class uses the concept of steep brane world inflation. We show that in both cases the Lyth bound can be evaded, despite the large tensor-to-scalar ratio of perturbations. The post-inflationary dynamics is consistent with nucleosynthesis constraint in these cases.