Gravity-Driven Acceleration of the Cosmic Expansion

TL;DR

This paper proposes that a dynamical Planck mass can cause the universe's expansion to accelerate through kinetic energy, offering a gravity-driven inflation model without requiring a potential or cosmological constant.

Contribution

It introduces a novel mechanism where a dynamical Planck mass induces cosmic acceleration via kinetic energy, providing a new perspective on gravity-driven inflation.

Findings

A dynamical Planck mass can lead to accelerated expansion.

The model can produce nonsingular bouncing universes.

Acceleration may be too weak to solve initial condition problems.

Abstract

It is shown here that a dynamical Planck mass can drive the scale factor of the universe to accelerate. The negative pressure which drives the cosmic acceleration is identified with the unusual kinetic energy density of the Planck field. No potential nor cosmological constant is required. This suggests a purely gravity driven, kinetic inflation. Although the possibility is not ruled out, the burst of acceleration is often too weak to address the initial condition problems of cosmology. To illustrate the kinetic acceleration, three different cosmologies are presented. One such example, that of a bouncing universe, demonstrates the additional feature of being nonsingular. The acceleration is also considered in the conformally related Einstein frame in which the Planck mass is constant.