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arXiv · 2512.19888

Observational constraints on early time non-phantom behaviour of dynamical dark energy

Sk. Sohail·Sonej Alam·Md. Wali Hossain
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Abstract

We investigate dynamical dark energy models that admit non-phantom behaviour at early times, including thawing, scaling--thawing, and effective fluid extensions. Using current cosmological observations, we find that late-time background parameters remain stable across all models. Time-dependent parametrizations such as CPL show a $\sim2\sigma$ preference for phantom evolution at low redshift. Imposing non-phantom scaling dynamics at early times leads to strong lower bounds on the potential steepness, $\lambda \gtrsim 20$--$30$, constraining the early dark energy density to below the percent level at matter--radiation equality. Consequently, early scaling behaviour does not alleviate the Hubble tension and is penalised by Bayesian model selection. Our results indicate that while late-time dynamics can mildly improve the fit, early non-phantom scaling is strongly disfavoured by current data.

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Sk. Sohail, Sonej Alam, Md. Wali Hossain. 2025-12-22. Observational constraints on early time non-phantom behaviour of dynamical dark energy. https://arxiv.org/abs/2512.19888

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