Non-perturbative gauge invariant scalar fluctuations of the metric in Higgs inflation from complex geometrical scalar-tensor theory of gravity

TL;DR

This paper explores gauge-invariant scalar metric fluctuations in Higgs inflation within a geometrical scalar-tensor gravity framework, showing nearly scale-invariant spectra consistent with Planck data and addressing the trans-Planckian problem.

Contribution

It introduces a non-perturbative, gauge-invariant approach to scalar fluctuations in Higgs inflation derived from complex geometrical scalar-tensor gravity.

Findings

Power spectrum nearly scale-invariant

Predicted spectral index and tensor-to-scalar ratio align with Planck 2018

Trans-Planckian problem can be avoided in this model

Abstract

In this letter we investigate gauge invariant scalar fluctuations of the metric in a non-perturbative formalism for a Higgs inflationary model recently introduced in the framework of a geometrical scalar-tensor theory of gravity. In this scenario the Higgs inflaton field has its origin in the Weyl scalar field of the background geometry. We found a nearly scale invariance of the power spectrum for linear scalar fluctuations of the metric. For certain parameters of the model we obtain values for the scalar spectral index $n_s$ and the scalar to tensor ratio $r$ that fit well with the Planck 2018 results. Besides we show that in this model the trans-planckian problem can be avoided.