Higgs-Dilaton Inflation in Einstein-Cartan gravity

TL;DR

This paper explores how Einstein-Cartan gravity influences Higgs-Dilaton inflation, revealing unique attractor behaviors and solutions due to torsion effects, which differ from metric and Palatini formulations.

Contribution

It demonstrates the impact of Holst and Nieh-Yan terms on inflationary predictions within Einstein-Cartan gravity, highlighting novel attractor solutions and the role of torsion.

Findings

Attractor-like inflationary behavior linked to field-space curvature.

Existence of an additional attractor from a cubic pole in kinetic term.

Distinct features of Einstein-Cartan formulation compared to metric and Palatini theories.

Abstract

We study the phenomenology of the Higgs-Dilaton model in the context of Einstein-Cartan gravity, focusing on the separate impact of the Holst and Nieh-Yan terms on the inflationary observables. Using analytical and numerical techniques, we show the predictions of these scenarios to display an attractor-like behaviour intrinsically related to the curvature of the field-space manifold in the metric formulation of the theory. Beyond that, the analysis of the Nieh-Yan case reveals the existence of an additional attractor solution induced by a cubic pole in the inflaton kinetic term that becomes relevant at large dilaton couplings. This constitutes a unique feature of the Einstein-Cartan formulation as compared to the metric and Palatini counterparts.