On a possible compensation of the QCD vacuum contribution to the Dark Energy

TL;DR

This paper proposes a mechanism involving a cosmological Yang-Mills field to counteract the large negative QCD vacuum energy contribution, potentially explaining dark energy, and links it to color confinement and instanton solutions.

Contribution

It introduces a novel compensation mechanism using a cosmological Yang-Mills field to address the QCD vacuum energy problem in cosmology.

Findings

The Yang-Mills field can offset the QCD vacuum energy contribution.

The solution involves finite-time instantons and relates to color confinement.

A free normalization constant is needed for exact compensation.

Abstract

We suggest one of the possible ways to compensate the large negative quantum-topological QCD contribution to the vacuum energy density of the Universe by means of a positive constant contribution from a cosmological Yang-Mills field. An important role of the exact particular solution for the Yang-Mills field corresponding to the finite-time instantons is discussed. An interesting connection of the compensation mechanism to the color confinement in the framework of instanton models has been pointed out. Besides the $\Lambda_{\rm QCD}$ scale, this proposal relies on one yet free dimensionless normalisation constant which cannot be fixed by the perturbative QCD theory, and thus should be fine-tuned for the exact compensation to hold.