One-parameter dynamical dark energy: Hints for oscillations

Understand

There is mounting evidence from multiple cosmological probes that dark energy may be dynamical, with an equation of state that evolves over cosmic time.

• While this evidence is typically quantified using the Chevallier-Polarski-Linder (CPL) parametrization, based on a linear expansion of $w(a)$ in the scale factor, non-parametric reconstructions frequently suggest non-linear features, particularly at late times.
• In this work, we investigate four minimal one-parameter models of dark energy with non-linear dependence on the scale factor.
• These models are constrained using Cosmic Microwave Background (CMB) data from Planck, lensing reconstruction from ACT-DR6, Baryon Acoustic Oscillation (BAO) measurements from DESI-DR2, and three Type-Ia supernovae (SNe) samples (PantheonPlus, DESY5, and Union3), considered independently.