Mass Generation for an Ultralight Axion

TL;DR

This paper calculates the mass of an ultralight axion arising from symmetry breaking in a supersymmetric gauge theory, proposing it as a candidate for explaining the small cosmological constant.

Contribution

It provides a theoretical calculation of the axion mass in a supersymmetric SU(2) gauge theory, linking it to cosmological observations of dark energy.

Findings

Axion mass is extremely small when gauge symmetry breaks at high energy.

Identifies the axion as a potential ultralight boson for dark energy.

Supports the ultralight axion hypothesis for cosmological constant explanation.

Abstract

If a global chiral symmetry is explicitly broken by anomalies in nonabelian gauge theories, a pseudo Nambu-Goldstone boson (axion) associated with a spontaneous breakdown of such a global symmetry acquires a mass through nonperturbative instanton effects. We calculate the axion mass assuming a supersymmetric SU(2) gauge theory and show that the axion obtains an extremely small mass when the SU(2) gauge symmetry is broken down at very high energy, say at the Planck scale. We identify the axion with a hypothetical ultralight boson field proposed to account for a small but nonzero cosmological constant suggested from recent cosmological observations.