Two scalar fields inflation from scale-invariant gravity with modified measure

TL;DR

This paper introduces a gravity-matter model with a non-Riemannian measure that naturally produces a two-field inflationary scenario with a flat potential region, leading to a viable inflationary period and potential for particle creation.

Contribution

It proposes a novel scale-invariant gravity model with a non-Riemannian measure, resulting in a two-scalar-field inflationary framework with distinctive potential features.

Findings

The model yields a flat inflationary potential with a minimum for current vacuum energy.

Two scalar fields can drive inflation and particle creation, respectively.

The number of e-folds can be constrained in future studies.

Abstract

A new class of gravity-matter model defined with an independent non-Riemannian volume form is studied, in the second order formalism. The action has a global scale invariance symmetry, which can be broken by the equation of motion of the measure fields. By a conformal transformation the theory transforms into a theory which governed by two independent scalar fields and a specific potential. When the scale invariance symmetry is not broken also in the equations of motion, only one field appear in the effective potential. This effective potential has a flat region which is responsible for the inflation, and it ends with a minimum, which is responsible for the present vacuum energy. In the general case, with a spontaneous symmetry breaking of the scale symmetry, one scalar field is responsible for the inflation and the other could be responsible for the particle creation. The first field (inflaton) can slowly roll, while the second field (curvaton) is more strongly coupled to the potential. The number of e-folds for both models is also dissuaded and could be constraint in the future.