Inflation with multiple vector fields and non-Gaussianities

TL;DR

This paper explores an inflation model with triplet vector fields, analyzing scalar and tensor perturbations, non-Gaussianities, and their observational constraints, highlighting the role of parity violation and vector field energy.

Contribution

It introduces a non-minimally coupled triplet vector field inflation model with parity violation, providing detailed predictions for power spectra and non-Gaussianities.

Findings

Vector fields contribute to gravitational wave spectra.

Parity violation induces chirality in gravitational signals.

Non-Gaussianities constrain model parameters.

Abstract

We consider a model of inflation consisting a triplet of $U(1)$ vector fields with the parity violating interaction which is non-minimally coupled to inflaton. The vector field sector enjoys global $O(3)$ symmetry which admits isotropic configuration and provides not only vector modes but also scalar and tensor modes. We decompose the scalar perturbations into the adiabatic, entropy and isocurvature perturbations and compute all power spectra and cross correlations of the scalar and the tensor sectors. The tensor modes associated with the vector fields contribute to the power spectrum of gravitational waves while the parity violating term generates chirality in gravitational power spectra and bispectra. We study nonlinear scalar and tensor perturbations and compute all bispectra and three-point cross-correlations. In particular, it is shown that the non-Gaussianity of curvature perturbations and gravitational waves are enhanced by the vector field perturbations. We show that non-Gaussianities put strong constraints on the model parameters such as the parity violating coupling and the fractional energy of the vector fields.