Successful Higgs inflation from combined nonminimal and derivative couplings

TL;DR

This paper introduces a Higgs inflation model combining non-minimal and generalized non-minimal derivative couplings, achieving a prolonged inflationary phase with low tensor-to-scalar ratio and stable scalar perturbations, avoiding previous issues.

Contribution

It presents a novel inflationary scenario that merges NMC and GNMDC, overcoming their individual limitations and ensuring stable, prolonged inflation with observationally consistent predictions.

Findings

Achieves long inflationary phase via gravitational friction from GNMDC.

Maintains low tensor-to-scalar ratio due to NMC.

Heals instabilities in scalar perturbations by NMC dominance.

Abstract

We propose an inflationary scenario based on the concurrent presence of non-minimal coupling (NMC) and generalized non-minimal derivative coupling (GNMDC), in the context of Higgs inflation. The combined construction maintains the advantages of the individual scenarios without sharing their disadvantages. In particular, a long inflationary phase can be easily achieved due to the gravitational friction effect owed to the GNMDC, without leading to trans-Planckian values and unitarity violation. Additionally, the tensor-to-scalar ratio remains to low values due to the NMC contribution. Finally, the instabilities related to the squared sound-speed of scalar perturbations, which plague the simple GNMDC scenarios, are now healed due to the domination of the NMC contribution and the damping of the GNMDC effects during the reheating era. These features make scenarios with nonminimal and derivative couplings to gravity successful candidates for the description of inflation.