Quintessence Axion Dark Energy and a Solution to the Hubble Tension

TL;DR

This paper proposes a model where electroweak axion energy accounts for dark energy and a gravitino dark matter candidate helps resolve the Hubble tension by decaying after recombination.

Contribution

It introduces a minimal supersymmetric model with electroweak axion and gauged symmetry to simultaneously address dark energy and the Hubble tension.

Findings

Axion energy density matches observed dark energy.

Gravitino with ~1 GeV mass can decay after recombination.

Decaying gravitino helps reconcile Hubble constant measurements.

Abstract

We present a model in which the question about a nature of the dark energy and the recently raised Hubble tension can be addressed at once. We consider the electroweak axion in the minimal supersymmetric standard model where the axion energy density is identified with the observed dark energy. Along with this, imposing a gauged $Z_{10}$ symmetry makes it possible to have a gravitino dark matter whose mass amounts to $\sim\mathcal{O}(1)\,\,{\rm GeV}$. We find that the gravitino with mass $\sim\mathcal{O}(1)\,\,{\rm GeV}$ can be a good candidate of a decaying dark matter of which decay after recombination can reconcile discrepancy in local measurements of the Hubble expansion rate $H_{0}$ and that inferred from the cosmic microwave background observation.