Primordial gravitational waves in DHOST inflation

TL;DR

This paper explores DHOST inflation models with shift symmetry, predicting potentially detectable primordial gravitational waves due to deviations from standard inflationary consistency relations.

Contribution

It introduces DHOST inflation models with broken shift symmetry, leading to unique tensor spectra and potential observational signatures.

Findings

Strong violation of single-field inflation consistency relation

Flat tensor spectrum with potential for future detection

Deviations from scale invariance in scalar and tensor perturbations

Abstract

We consider DHOST inflationary models with a shift symmetry leading to a de Sitter space-time at the background cosmological level. Deviations from scale invariance of the scalar and tensor perturbations follow from the breaking of the shift symmetry by quadratic and quartic operators. These models show a strong violation of the consistency relation of single-field inflationary models with a very flat spectrum of tensor perturbations. This opens up the prospects of future detection of primordial gravitational waves by mHz experiments.