Towards a classification of UV completable Higgs inflation in metric-affine gravity

TL;DR

This paper classifies UV-completable Higgs inflation models within metric-affine gravity, analyzing particle spectra and identifying parameter regions that avoid ghosts and tachyons, thus advancing understanding of consistent high-energy inflation theories.

Contribution

It provides a classification framework for UV-completable Higgs inflation in metric-affine gravity and identifies healthy parameter regions free of instabilities.

Findings

Identified parameter regions with healthy particle spectra

Demonstrated how small deformations affect dynamical fields

Found conditions to avoid ghosts and tachyons in the theory

Abstract

Towards a classification of UV completable Higgs inflation in the framework of parity-even metric-affine gravity, we investigate the particle spectrum of a deformed theory in the large-$N$ limit. In a simple Higgs inflation model in metric-affine gravity, it is known that its UV cutoff is much smaller than the Planck scale. While it calls for UV completion, a concrete example has not yet been found, even with the large-$N$ limit known as a successful technique to complete an original Higgs inflation defined on the Riemannian geometry. This motivates us to study how small deformation of the simple Higgs inflation affects the emergence and properties of dynamical fields particularly in the large-$N$ limit. As a UV theory has to be free of ghosts or tachyons at least around Minkowski space, we perform the parameter search and find the healthy parameter region where a new heavy particle can propagate without these pathologies.