Updated cosmological constraints on axion dark energy with DESI

TL;DR

This paper updates constraints on axion dark energy parameters using DESI data, finding they are consistent with theoretical expectations and supporting the dynamical dark energy hypothesis, though Bayesian evidence favors the simpler $w_0w_a$ model.

Contribution

It provides the first comprehensive cosmological constraints on axion dark energy parameters incorporating the latest DESI data.

Findings

Axion parameters are constrained to ultralight mass regime.

Results support the dynamical dark energy scenario.

Bayesian analysis favors phenomenological $w_0w_a$ model over axion dark energy.

Abstract

We present updated constraints on the parameters of an axion dark energy model, for which we took into account the properties of its characteristic potential and its full cosmological evolution. We show that the values of the axion parameters appear sufficiently constrained by the data, including the latest DESI DR1, and are consistent with the theoretical expectations of a field mass $m_a$ in the ultralight regime $\log (m_a c^2/~\mathrm{eV}) \simeq -32.60~\pm~0.12$, and an effective energy scale $f_a$ close to the reduced Planck energy $\log (f_a/~ M_\mathrm{Pl}) \simeq -0.28~\pm~0.19$. Our results also support the idea of dynamical dark energy, although Bayesian evidence still favors the phenomenological dark energy model $w_0w_a$ over the axion dark energy, with the Bayes factor indicating moderate and weak strength of the evidence, respectively, when the models are compared to the cosmological constant $\Lambda$. However, the results suggest that axion dark energy remains a well-motivated model and its parameters may be better constrained if the upcoming DESI data show further evidence for dynamical dark energy.