Dynamical dark energy in the no-scale Brans-Dicke gravity

TL;DR

This paper introduces a new scalar field in no-scale Brans-Dicke gravity with symmetry breaking, enabling it to act as dark energy and linking it to inflation and reheating, consistent with recent observations.

Contribution

It proposes a novel scalar field with symmetry breaking in no-scale Brans-Dicke gravity that can explain dark energy and connect to inflationary models.

Findings

Scalar field acts as quintessence for dark energy.

Model achieves super-Planckian decay constant compatible with observations.

Incorporates inflation and reheating mechanisms.

Abstract

We add a new scalar field in the no-scale Brans-Dicke gravity and require it to have a global O(2) symmetry with the original scalar field in the Brans-Dicke gravity. This gives us a new massless scalar field in the Einstein frame due to the SO(2) symmetry. We then explicitly break the O(2) symmetry to a $D_4$ symmetry, and this scalar field gains a periodic potential. This scalar field can serve as the quintessence field to explain dark energy. If we further add the $R^2$ term and the non-minimal coupling to the Higgs field, we can realize inflation and reheating, and this leads to a super-Planckian decay constant of the quintessence potential. The super-Planckian decay constant is consistent with the newly released observational data according to a recent analysis.