Mutated hilltop inflation revisited

TL;DR

This paper re-examines mutated hilltop inflation using Hamilton-Jacobi formalism, revealing two inflationary regimes with distinct observational predictions and showing its similarity to $ppa$-attractors.

Contribution

It provides a detailed analysis of mutated hilltop inflation dynamics and observational predictions, highlighting its connection to $ppa$-attractor models.

Findings

Two types of inflationary solutions identified: small and large field.

Predicted tensor-to-scalar ratio varies from negligible to high amplitude.

Inflationary observables are consistent with current data across parameter ranges.

Abstract

In this work we re-investigate pros and cons of mutated hilltop inflation. Applying Hamilton-Jacobi formalism we solve inflationary dynamics and find that inflation goes on along the ${\cal W}_{-1}$ branch of the Lambert function. Depending on the model parameter mutated hilltop model renders two types of inflationary solutions: one corresponds to small inflaton excursion during observable inflation and the other describes large field inflation. The inflationary observables from curvature perturbation are in tune with the current data for a wide range of the model parameter. The small field branch predicts negligible amount of tensor to scalar ratio $r\sim \mathcal{O}(10^{-4})$, while the large field sector is capable of generating high amplitude for tensor perturbations, $r\sim \mathcal{O}(10^{-1})$. Also, the spectral index is almost independent of the model parameter along with a very small negative amount of scalar running. Finally we find that the mutated hilltop inflation closely resembles the $\alpha$-attractor class of inflationary models in the limit of $\alpha\phi\gg 1$.