Inflation and Linear Expansion in the Radiation Dominated era in Jordan-Brans-Dicke Cosmology

TL;DR

This paper explores a cosmological model within Jordan-Brans-Dicke theory, revealing a universe that begins closed and exponentially expands, then transitions to linear expansion with potential scale-invariant phases, influenced by matter presence.

Contribution

It introduces a scale-invariant cosmological model with a quartic potential, detailing the universe's expansion phases and effects of matter on dynamics.

Findings

Radiation dominated era begins with a closed universe.

Late radiation era expands linearly.

Presence of matter causes deceleration.

Abstract

We present several features of a cosmological model based on the Brans-Dicke-Jordan-Thirry action which is scale invariant with a quartic potential for the Jordan scalar field. We show that the radiation dominated era starts with a closed universe which expands exponentially and the late radiation dominated era expands linearly. We find that there may be a scale-invariant phase with stiff matter between these two radiation dominated eras. The introduction of matter in the linearly expanding universe causes deceleration.