Dynamic vacuum variable and equilibrium approach in cosmology

TL;DR

This paper introduces a modified gravity model with a dynamic vacuum variable that oscillates and diminishes over time, potentially explaining the observed vacuum energy and dark matter in the universe.

Contribution

It presents a novel cosmological model where the vacuum energy density oscillates and decreases, aligning with observed values and suggesting a link to dark matter.

Findings

Oscillating vacuum energy density with decreasing amplitude

Agreement of average vacuum energy with observed near-critical density

Potential contribution of oscillating vacuum to dark matter

Abstract

A modified-gravity theory is considered with a four-form field strength F, a variable gravitational coupling parameter G(F), and a standard matter action. This theory provides a concrete realization of the general vacuum variable q as the four-form amplitude F and allows for a study of its dynamics. The theory gives a flat Friedmann-Robertson-Walker universe with rapid oscillations of the effective vacuum energy density (cosmological "constant"), whose amplitude drops to zero asymptotically. Extrapolating to the present age of the Universe, the order of magnitude of the average vacuum energy density agrees with the observed near-critical vacuum energy density of the present universe. It may even be that this type of oscillating vacuum energy density constitutes a significant part of the so-called cold dark matter in the standard Friedmann-Robertson-Walker framework.