Higgs-Dilaton Inflation in Einstein-Cartan gravity

Matteo Piani, Javier Rubio


We study the phenomenology of the Higgs-Dilaton model in the context of EinsteinCartan 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.