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arXiv · 2503.18120

Dynamical dark energy from an ultralight axion

Hoang Nhan Luu·Yu-Cheng Qiu·S. -H. Henry Tye
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Abstract

Recently the Dark Energy Survey (DES) Collaboration presented evidence that the equation of state $w$ of the dark energy is varying, or $w \simeq -0.948$ if it is constant. In either case, the dark energy cannot be due to a cosmological constant alone. Here we study an ultralight axion (or axion-like particle) with mass $m_\phi \simeq 2 \times 10^{-33}$ eV that has properties that can explain the new $w$ measurement. In particular, $w\ge -1$ and a negative cosmological constant $\Lambda < 0$ is preferred in this model. We also present a simple formula for $w$ for the model to ease data fitting.

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Hoang Nhan Luu, Yu-Cheng Qiu, S. -H. Henry Tye. 2025-03-23. Dynamical dark energy from an ultralight axion. https://arxiv.org/abs/2503.18120

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