Electrically charged curvaton

TL;DR

This paper explores a curvaton model with a Standard Model hypercharge charge, linking early universe dynamics to particle physics, and analyzes its potential to generate observed density perturbations while considering new physical effects.

Contribution

It introduces a curvaton mechanism with an electric charge under the Standard Model hypercharge, incorporating gauge interactions and analyzing their impact on primordial perturbations.

Findings

Charge fluctuations are screened during inflation, avoiding observational constraints.

The model can produce the observed density perturbations at high Hubble rates.

Non-Gaussianity levels exceed observational bounds, indicating the need for non-linear analysis.

Abstract

We consider the possibility that the primordial curvature perturbation was generated through the curvaton mechanism from a scalar field with an electric charge, or precisely the Standard Model U(1) weak hypercharge. This links the dynamics of the very early universe concretely to the Standard Model of particle physics, and because the coupling strength is known, it reduces the number of free parameters in the curvaton model. The gauge coupling also introduces several new physical effects. Charge fluctuations are generated during inflation, but they are screened by electron-positron pairs therefore do not violate observational constraints. After inflation, the curvaton interacts with thermal radiation which destroys the curvaton condensate and prevents the generation of curvature perturbations, unless the inflaton dynamics satisfy strong constraints. The curvaton also experiences a period of parametric resonance with the U(1) gauge field. Using the standard perturbative approach, we find that the model can generate the observed density perturbation for Hubble rate H_* > 10^8 GeV and curvaton mass m > 0.01 H_*, but with a level of non-Gaussianity (f_NL > 130) that violates observational constraints. However, previous studies have shown that the parametric resonance changes the predicted perturbations significantly, and therefore fully non-linear numerical field theory simulations are required.